MadModder
Gallery, Projects and General => Project Logs => Topic started by: raynerd on October 24, 2009, 04:03:06 PM
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I fancy having a go at making a clock wheel of course building up to my long term plans of a full clock build but before I can even consider the wheel, I`d need to make the cutter. In my plans that I ultimately want to use, the plans specify the wheel Pitch circle diameter, number of teeth and module cutter to use. Consequently I`ll need to make the specific cutter determined by the "module", so I decided to try and make a 0.8 module cutter and find the measurements to make the cutter! I had some learning to do and this is what I found:
(http://www.raynerd.co.uk/images/cuttt1.jpg)
So the most important measurements as far as I can see are:
1. dedendum - the distance between the bottom of the tooth to the pitch circle diameter.
2. addendum - distance between pitch circle diameter to the end of the tooth
3. Distance between tooth = (normally) = width of tooth
4. Radius of arc that forms the tooth.
Obviously this changed a little when your making the cutter as of course your cutting the gap and consequently forming half of two adjacent teeth.
I then found this site which has lots of formula for how the module relates to these dimensions. I can`t find a link to the site but I saved the image, here is the table:
(http://www.raynerd.co.uk/images/cuttt2.jpg)
So that kind of helped but now got me a bit hung up on this idea of module, as to me the minute you specified a module I expected that you were specifying or dictating a specific wheel (I thought this due to the link in the formula) needless to say I was wrong. It took me a while but I put together this spreadsheet which gave me examples of using the same module on two different sized wheels - so I used a module 0.5 cutter on a 1 pcd and 2 pcd wheel and then did the same calculations but using a 1 module cutter.
http://www.raynerd.co.uk/images/Gearing.xls
This proved in my head that in actual fact the module DOES dictate the tooth dimensions, simply if you’re using another sized wheel you are just adding teeth onto that wheel but with the same profile. Now I was happy that the module cutter is a specific cutter for a specific tooth form. I then calculated the dimensions for a 0.8 module cutter which is what I wanted to make - this is on the far right of the spreadsheet.
There are currently no formula in the spreadsheet but I am working on adding this (that is what the notes page is for) and if I finish it, I`ll post it up. I used a pen and calc and simply used excel to tabulate the info.
OK, well now I have the dimensions for the 0.8 module cutter:
Tooth arc diameter required would be 2.51968 mm (it was actually worked out as a radius for the arc but the way I`ll be forming it, described later will require the diameter). The addendum for this tooth profile is 0.0424 inches (1.07696 mm) and the dedendum is 0.0496 inches (1.25984 mm). Gap between teeth is 1.25mm
I have heard good things about John Shadle's wheel cutter as it is fully supported. The standard single point/tooth flycutter style is said to often brake and if it blunts during cutting, resharpening often changed the size. John's version is really clever as the forming tooth is fully supported by the body of the cutter:
http://onlineclockbuilding.com/DOWNLOADS/flycut.rtf
....... and sometimes I can do maths, but from here on in I am a novice. I`ll let the pictures do most of the talking:
My slither of apparently silver steel that I picked up from the scrappy. 2inc dia and about 8mm thick. Little bit of steel round stock to be used as the madrel:
(http://www.raynerd.co.uk/images/cutt.JPG)
Making the mandrel:
(http://www.raynerd.co.uk/images/cutt1.JPG)
Mistake number one - I threaded the mandrel, I think M8 and tried to hold the steel blank. Whenever I hit something a bit tought it just spun the disk. When I tried to tighten the bolt I threaded it and it just spun! Why did I thread it and did I do something wrong?
(http://www.raynerd.co.uk/images/cutt2.JPG)
Steel blank being drilled:
(http://www.raynerd.co.uk/images/cutt3.JPG)
So I had to drill the mandrel fully through and bolt the steel blank on using a bolt pulling it all the way through. It worked a treat but wasn`t as neat as my original idea.......comments appreciated:
(http://www.raynerd.co.uk/images/cutt4.JPG)
Then I used my parting off, grooving tool to cut the dedendum on each side to the correct depth and also gain the correct tooth gap or in this case, width of the tip of the cutter:
(http://www.raynerd.co.uk/images/cutt5.JPG)
Then I needed to put the radius on which I did using a 2.5mm drill bit. I made a template by drilling a 2.5mm hole and cutting it in half. I was going to use that tool next to it but it was too hard to get it to size.
(http://www.raynerd.co.uk/images/cutt6.JPG)
So I used an old 2.5mm drill and hand ground the radius on the end. I`m sure there must be a more accurate way but this is how John described doing it. I got it quite accurate and it seemed to fit the template well, it was just fiddly and very hard to mount in the tool post:
(http://www.raynerd.co.uk/images/cutt7.JPG)
I then prodded the sides to add the addendum that would create the tooth tip profile:
(http://www.raynerd.co.uk/images/cutt8.JPG)
Then dismanltled it all:
(http://www.raynerd.co.uk/images/cutt9.JPG)
Then chopped it in half and started to give it some profile:
(http://www.raynerd.co.uk/images/cutt10.JPG)
Then I drilled the off-set mounting hole and I think you can see the tip profile on this photo. I still have some sharpening and profiling to do but it is there! If you open the link I sent of John's article you will see that by mounting this off set hole in the arbor you automatically create relief below the cut.
(http://www.raynerd.co.uk/images/cutt11.JPG)
So, there we go!
Will it cut a wheel? Is it silver steel (seems very soft, definitely needs hardening!)?
I`m not too sure but I feel good that I`ve made it! Next job is to harden it and I may even purchase some case hardening compound.
What is the best way to mount this on the arbor? I just think that if I thread a hole on a mandrel it will spin and not hold properly like when I tried mounting the original blank earlier in the post. I could do with a key way or perhaps bolt it in two places...any suggestions?
All the best.
Chris
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Nice going Chris
You've certainly jumped in with this one. Makeing a clock is something I wan't to have a go at, I've read a number of diferent methods for making the tooth cutter, one thing that struck me is the crudness of the methods. I think of a clock as a presition instrument, but when you read how they made early clocks you realise that even using crude methods and the minimum of tooling you can make an intrument that will keep accuratle time.
Any way if it is silver steel the fly cutter is made of it won't case harden. What you need to do is heat it to cherry red and quench it in water, then polish it up, then yoo need to aneal it back a bit, to do this heat it up again on a bed of sand (this slows the temp rise) until its a straw colour then quench it again in water.
You need to make the arbour with a plain diameter thats a nice fit on the cutter with a short threaded length to take the bolt it will look like this
(http://i431.photobucket.com/albums/qq32/sbwhart/Tool%20Post%20Grinder/100_2602.jpg)
Hope this helps
Stew
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Stew, thanks for the help. So basically I need an external thread that I can slip the cutter onto it and then bolt up. Would you bolt up directly against the cutter or would you slip on a washer to give more surface contact against the cutter. I can just imagine it not locking it tight enough and when it comes to cutting the wheel it spinning the cutter around rather than making the cut. I know commercial cutters have a notch or keyway in the mandrel and cutter to stop it spinning.
Chris
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Yes a washer would be a good idea :thumbup:
Stew
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Thankyou :wave:
Got half term week off so I should give this a go over the next few days.
I`m still questioning whether this was silver steel - seems on the softer side.
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On hardening I have been advised once to heat to cherry red and quench and then anneal by putting it in the deep fat frier ( chip maker) cold then heat to max for 30min and turn the power off. This is supposed to heat slowly to 190-200 deg and then cool slowly.????
I have never tried it because I have always heated it so just the cutting end is cherry red so -hardening only the tip.
About slipping -A washer and nut should do just feed slowly as the cutting pressure would be interupted.
Hope some of this helps.
Gerhard
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Geroli - with the tip on my cutter being fully supported I wondered also whether to head the cutting edge to cherry red and not aneal it. It will be brittle but very hard and unlikely to shatter because of the cutter shape... ?
Chris
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:(
Stew, just spent a while in the shop making an arbour for this cutter as you suggested. The hole in the cutter is 5mm so I made the arbour and threaded it M5. As I predicted (because it has happened to me before) when I came to tighten up the bolt against the cutter and put some proper force against it, the bolt just started to spin and ruin my thread!
I`m using an M5 domer die but something is clearly not right with my thread. Any suggestions - as I described in my first post this also happened the other way around when I threaded my bore in the mandrel to hold the cutter blank when I tightened up the bolt it started to spin in the hole.
I`m using force but nothing excessive....
Anyone help?
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Chris, is there enough room on the face of the mandrel and in the tool to fit an off-centre locating peg? Then, you wouldn't have to clamp up so hard - the peg, not the tightness of the bolt, would stop the tool spinning.
Looking at your tool, it strikes me that if it does turn out to be silver steel, the tip might be a bit brittle if you don't temper after hardening it, particularly with the constant hammering of an interrupted cut.
Andy
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Would you bolt up directly against the cutter or would you slip on a washer to give more surface contact against the cutter. I can just imagine it not locking it tight enough and when it comes to cutting the wheel it spinning the cutter around rather than making the cut.
Chris
Cupping the washer slightly will increase the pressure on its periphery when the screw is tightened.
Joe
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Chris
Don't know what your doing wrong can you post a pic of the bits to give us a clue.
Stew
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:(
Stew, just spent a while in the shop making an arbour for this cutter as you suggested. The hole in the cutter is 5mm so I made the arbour and threaded it M5. As I predicted (because it has happened to me before) when I came to tighten up the bolt against the cutter and put some proper force against it, the bolt just started to spin and ruin my thread!
I`m using an M5 domer die but something is clearly not right with my thread. Any suggestions - as I described in my first post this also happened the other way around when I threaded my bore in the mandrel to hold the cutter blank when I tightened up the bolt it started to spin in the hole.
I`m using force but nothing excessive....
Anyone help?
Hmm.. what are the dimensions(diameters) you use, when making an M5 thread :scratch:? Be it tapping or an external thread?
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Hi Guys, I`ll post a picture later, I`ve been at a family part all afternoon. I can thread the bolt on tight and then when I come to give it the extra "nip" it turns the bolt about half a turn and loses any sort of torque. I guess it must be stripping the thread? I`ve re-done it but I don`t dare give it that extra that it needs, it is really tight so I think I`m going to go with AndyF suggestion of an offset locating pin. Basically I have room to put in a short M4 stub off centre that will butt up against the cutter and give me added piece of mind that it isn`t going to slip.
Picture later.
Chris
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Ok well, here it is at present. Sorry picture is rubbish, taken on my phone as I didn`t have the camera handy:
(http://www.raynerd.co.uk/images/cutt15.JPG)
(http://www.raynerd.co.uk/images/cutt16.JPG)
This new thread seems to have tightened up much better but I still don`t want to put on the extra little nip for fear of stripping it. As you can see on the photo, there is plenty of room to add a small pin at the bottom to stop it rotating. Now, I must confess, being new to this hobby I like to ensure everything is the best it can be for practice and if it isn`t, I start again but I did have a quite useful accident. I went to thread the ofset pin hole and I picked up one of my cheapo m4 taps, needless to say it snapped in the hole but with about 15mm depth and left a little stub about 4mm above the surface sticking out! Now I did consider grinding this flat and tapping the other side but to be honest, although it was a dreadful mistake, it is serving an excellent purpose so I` going to leave it. No picture but again I`ll take on tomorrow. I think this bolt has actually locked it up but at least I know it won`t spin with the stub in place.
So next job tomorrow is to try and harden it and then it should be ready for a trial wheel run. Certainly looks good and a bit of fine tuning of the method I should be able to make some pretty accurate cutters. I think I`ve learnt a lot from making this one.
Chris
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Chris, the end-on pic shows why holding it by a single nut is probably doomed to failure. The tool-tip will hit the work on the interrupted cut, and any tiny shift of the tool will be anti-clockwise. That will tend to loosen the nut, and the next contact will make things worse, so you will end up with the arbor rotating and the tool stationary :(.
Thinking about it, it might have been better to drill and tap the end of the mandrel and use a bolt to secure the tool. Your nut is probably only about 4 or 5 threads deep, and common or garden nuts are often a sloppy fit and made of something almost, but not entirely, quite unlike proper steel. A bolt 15mm into the mandrel would engage over about 18 threads. That might solve the stripped thread problem, though the tool and bolt would still be knocked anti-clockwise in the absence of something like a pin to support the tool.
Andy
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Do you know that the cutter is mounted in the wrong direction for cutting?
If it was the other way around, it would be trying to tighten the nut rather than undo it.
Bogs
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No I didn`t, thanks for pointing it out! I`ve just flipped it around now and understand exactly what you mean. I didn`t consider that :doh:
Chris
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Chris,
Also, when making the arbor, did you do it with an accurate plain diameter that fits into the hole in the cutter?
I noticed that when you made your arbor for making the cutter you didn't really, it was just mounted on the thread of the bolt which isn't the most accurate. Also, you then took it out of the chuck, losing any concentricity you had machined into it. So the trick for machining outside profiles is to have the component you are machining ready to bolt onto the arbor and once you have turned the accurate location diameter, you don't take it out of the chuck, mount the component on it and gently turn the OD. You have to watch the rigidity and take light cuts here though otherwise you'll get chatter and will mess the whole thing up depending on how good the arbor design is. This is the way I do things like flywheels and loco wheels etc.
What are you going to make the clock wheel out of? Presumably it's going to be very thin so you'll be taking extremely light cuts I would imagine anyway?
Nick
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Nick - it will be 16g (1.55mm) CZ120 brass plate.
I`ve been reading over your post and I think, if I have read your post correctly, that that is what I did with this cutter. I machined the diameter, fitted the cutter on and then continued to take it down a fraction to the threading dia without taking it out of the chuck..... is this what you mean?
Chris
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Yeah that's right Chris, sorry, I just wasn't sure whether you did, that's the best practice. I suppose you didn't need to go to those lengths of accuracy when you were just making the profile for the cutter itself.
Good work.
Nick
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Yes Chris, good work, I'm following too with interest.
Agree about using a bolt an not the nut though :thumbup:
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Just a quick note as I think I need a lesson in arbours.
I`ve gone right back to Stews first post where he shows a picture of an arbour. Can someone explain, if your cutter, tool, wheel blank ... whatever you are mounting is sat on the nice polished surface with no thread, clearly the bolt isn`t going to be able to be threaded down all the way to clamp it up. So what is normally used to apply the pressure from the bolt onto the piece being held.
I`ve drawn a crappy exadurated diagram incase I`m not making any sense:
(http://www.raynerd.co.uk/images/madrel.JPG)
Darren - sorry, what are you agreeing with? I thought I should be threading the rod and using a nut not a bolt like I intially did to hold the wheel blank?
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The length of the plain diameter on your arbor should be marginally less than the thickness of the cutter. You could always put another nut on to lock it but as bogs said, it will try to tighten rather than loosen.
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:doh: obvious now! Ta
Chris
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When making arbors like you have, and if they are made to be used again with different thickness cutters, then you would make a recessed washer for each thickness of cutter you are going to be using.
The C-o-C below should explain it. It can be used with a threaded arbor as well as one used with a bolt.
Bogs
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Thank you John - I now understand perfectly and that has also cleared up what Darren said about the bolt and not a nut. Since the cutter is sitting on the plain diameter section true to the main body of the arbour, the bolt is just there to lock it on yet won`t effect it running true... :thumbup:
Thanks... that really helped. I`ll let you know how it goes...
Chris
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With a single point tool as you are contemplating using, and because you are only cutting thin material, even if the tool was wobbling about all over the place, it shouldn't really matter, because the tool will be in the same position in the short arc of rotation you are cutting in.
It only makes a real difference when you have multi point tools or long distances to cut, then everything should be running flat and concentric.
Bogs
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Chris,
Referring back to John's sketch, Do you recall how some of the cheap slit saw arbours work? They have a stepped series of shoulders for the differing size of hole in the blade, then use a recessed washer.....
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Do you recall how some of the cheap slit saw arbours work? They have a stepped series of shoulders for the differing size of hole in the blade, then use a recessed washer.....
John, any day previous I would have said no but I was in RDG today and coincidently picked one up while browsing in their little pots of goddies. I don`t actually own a slitting saw, it is on my "to buy" list, so this is really my first use of an arbor of any sort. Infact, as you have tried to highlight, if I would have used a slitting saw in the past I think I would have had a better understanding.
Thanks again for your input...feel like I`m getting somewhere with all this.
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Continuing with the clock wheel cutter, I`ve posted the rest of my progress in the pictures below. I do try and take the advice given to me (although perhaps misinterpreted) and I have remade the arbor and also used the same idea for the clock wheel arbor but using a 2MT soft steel blank. Now I was much happier with my cutter arbor but with the constant interrupted cut I decided I had room to fit a M3 screw off-centre so I have also included this in the new arbor. It makes it look more cluttered but in terms of functionality, at least there is no chance of the cutter slipping.
The conversation primarily with Stew has made me think about a few things in terms of the error transferred when moving the arbor from the lathe for cutting and truing to the rotary table for cutting the teeth. One option was to mount the wheel arbor in the chuck and use a MT chuck adaptor for the rotary table to simply shift the chuck from the lathe to the RT. My adaptor I made had bad run-out and although I was prepared to pay Chronos price of £35 for the Boxford adaptor or attempt to remake it I thought the method I have used would be equally as good with limited error. Also, my chucks are bulky and mounting a chuck on the rotary table reduces available space. What I did do is shown below, putting the 2MT wheel arbor in a 3MT sleeve and mounting directly in the boxford headstock. I used an open sleeve and my intention is to pull the arbor through with a long drawbar - unfortunately, I didn`t have anything long enough so for now I used live centre (probably not best as it was pushing on the bolt) but in actual fact, it was held solid and didn`t spin just in the MT alone.
The new cutter arbor and cutter:
(http://www.raynerd.co.uk/images/cut10.JPG)
(http://www.raynerd.co.uk/images/cut11.JPG)
(http://www.raynerd.co.uk/images/cut12.JPG)
The wheel arbour with a 2MT in a 3MT sleeve mounted in headstock. Proded to get it roughly to size and shape it into a wheel.
(http://www.raynerd.co.uk/images/cut13.JPG)
..and then taken down to size. It looked to be running true using the live centre but should be more accurate when using the draw bar:
(http://www.raynerd.co.uk/images/cut14.JPG)
Hummm, then wondered how the hell I was going to get it all out! I went to have a look in the box that came with the boxford and found this lying next to the collet draw bar - just the job!
(http://www.raynerd.co.uk/images/cut15.JPG)
So this is what I have so far ... now need to harden and fine tune the cutter and then mount the wheel arbour directly in the rotary table 2MT centre
(http://www.raynerd.co.uk/images/cut16.JPG)
Any advice or comments more than welcome. Have I overlooked where error is going to creep in with this method, in my mind this would be as accurate as moving the arbor mounted in the chuck and shifting the chuck from lathe to rotary table.
Cheers
Chris
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Chris,
That bar is what I refer to as a "Linear Taper Remover" :D :D (There is a story that goes with that name.)
Joe
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Did the trick anyway :ddb:
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Making nice progress Chris :thumbup: when you come to cut the teeth dont forget to sadwitch the blank between a couple of backing plates or you will end up with bent gear teeth. And give the mystery steel cuter a try out on a bit of scrap brass first.
Good luck
Stew
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Yes, thanks for the reminder ... I`ll need to modify my arbor to suit. Probably just a case of extending the mounting section. I`ve seen this done a couple of ways, I`ve seen them cut without any support, I`ve seen them cut by sandwiching between two thicker disks of the root diameter allowing you to take a cut up to the support disk for the correct depth of cut and I`ve also seen the blank backed up against a thicker wooden sacrificial backplate. I`m strongly considering using the later as the wooden backplate really supports everything and stops the teeth bending back as the cutter tries to push to formed teeth back. I once went to a clockbuilders house a few years ago and this was the method he adopted.
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Looking really good Chris :thumbup:
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As Stew advised, or at least a varient, I need something to back the whole thing so that the brass teeth don`t bend under the force of the cutter. I have decided to back it with a piece of sacrificial wood. The cutter will follow through the brass into the wood and so will support the teeth from bending. I`ve seen this used in practice so I know it can work .... whether I can do it is a different story!
This is the wood I`m going to use with the wheel sat on top of it:
(http://www.raynerd.co.uk/images/wood1.JPG)
After some working on the wood (don`t like them damn brown flakes, they get everywhere!!) I got it down to size. I also used a thick brass sheet off-cut, turned it into a washer and mounted this at the front of the plate. This seemed to work really well, everything looks to be held down flush, running true and secure.
(http://www.raynerd.co.uk/images/wood2.JPG)
I then mounted the wheel blank in my RT and used a draw bolt to pull it through and clamp it down. Just need to change the chuck to my er32 collet chuck, mount the cutter and off I go .... in theory!
(http://www.raynerd.co.uk/images/wood3.JPG)
I also hardened the cutter this evening so tomorrow I really a ready to give it a whirl!
Chris
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That setup looks great to me Chris. Good luck. So is this just proving a theory, or are you going to start whittling up the rest of the clock wheels if this works?
Nick
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Looking good so far ... be interesting to see how this goes ... :dremel:
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Good luck Chris! :thumbup:
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Looking good Chris
Just check that the job is standing away from the RT far enough for the cutter to clear, its not a bad idea to rig a stop up on the table so that you dont run the cutter into the RT, gives you one less thing to worry about, when cutting a lot of teeth you want to focus on geting the indexing right.
Hope this helps
good luck
Stew
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Cheers guys ...
Nick - if this works then yes the aim is to start the clock since the wheels are a major part of the battle!
Stew - yes I can imagine a stop would be useful as running the cutter into the RT is something I could do!
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I wouldn`t call it a complete disaster, I did end up with something that loosely resembles a clock wheel but I have a long way to go so before I start, please feel free to post any comments, criticisms or advice. The more the better!
OK - so all the equipment was setup as shown in previous pictures. I also centered the cutter to the wheel centre and also leveled it square with the wheel blank. Stew mentioned above the issue of running the cutter too far and into the rotary table but once I set it up I realised there was no possibility of this happening as I was only moving the wheel blank into the cutter on the Y axis. So as I feed the Y axis, the tooth gap begins to form
(http://www.raynerd.co.uk/images/wheel1.JPG)
The first issue arose as I started taking the second cut, I didn`t get a picture of it but the teeth seem bent and not straight! The first tooth to form looked more bent than the others so I don`t know why this happened! Perhaps my cutter is profiled at an angle and is therefore cutting wonky teeth? OR, and I could check this, is the cutters cutting area, i.e the cutter tooth, not at 90 deg to the arbor?? I think this is most possible but will need to check it again tomorrow. This will explain why the teeth are at a little angle but not why the teeth look a little bent and especially the first!
Well I know this wasn`t going to be used in my clock but I wanted to finish it to see what other problems arise:
(http://www.raynerd.co.uk/images/wheel2.JPG)
Tooth form looks quite good so far!
Look at the first tooth and how bent it is ... obviously it is the furthest one away from the current cut in the next photo:
(http://www.raynerd.co.uk/images/wheel3.JPG)
Then I finally got back to the start and that was just using 6 deg divisions on my RT, soon I`ll need to use a dividing plate and that should help a lot with spacing.
(http://www.raynerd.co.uk/images/wheel4.JPG)
Next problem is the brass and how the cut is being taken. The brass is being bent rather than shaved or cut off. Notice how the teeth look a little convex ... not sure why this is happening BUT this is a scrap piece of brass and not the recommended CZ120 for clock wheels. Could this be the reason but look at the little bits that have been pushed forward and back instead of cut off. This is a major problem and needs sorting.
(http://www.raynerd.co.uk/images/wheel5.JPG)
Notice the two teeth that a very close together at the top, this is where I made my final cut to come back around to the finish. I a dividing head will help here but I`m a little unsure why this happened as the error was not carried forward as I was simply cutting every 6 deg rather than adding up any errors...if that makes sense? Also the first tooth being bent doesn`t help the issue...
(http://www.raynerd.co.uk/images/wheel6.JPG)
Then I had a brain wave, popped it back in the lathe to skim off these bits off the front of the teeth gap. What an idiot :bang: I caught the teeth tips with the cutting tool and stripped off the nice radius....from now on in the pics the top of the tooth profile looks flat, that is my fault!
Then it was time to strip off the wooden support. WOW the brass really had just been pushed back and not cut off! It was literally bent into the wood:
(http://www.raynerd.co.uk/images/wheel7.JPG)
Then tidied it up a little more and now it looks like this:
(http://www.raynerd.co.uk/images/wheel8.JPG)
Like I said, not a total failure, I learnt a lot but I have a lot of issues to sort out as this would be nowhere near good enough. I wonder if the brass type has a lot to do with it, maybe using the cz120 would cut rather than bend back?
Any thoughts.....?
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Just reading back on my post, should I be feeding the wheel blank into the cutter on the X axis?
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Just reading back on my post, should I be feeding the wheel blank into the cutter on the X axis?
Yes, I thought that was what you were going to do! :scratch:
You need to rough out the profile, then go round again with a very sharp finishing tool.
My 2 pennorth...... :thumbup:
David D
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Hmm. The teeth do seem to be a bit bent over in a slightly spiral shape. I wonder if, as you go round and start each new cut, the bending occurs because one flank is supported by solid brass where you haven't yet made a cut, whereas the other has less support, because the previous cut is there?
You could try going round a first time making every other cut, then a second time to fill in the gaps. But that might cause a similar effect, with each pair of teeth splaying out away from the cutter on the second time round. Or you could try going round and round, just nicking the periphery the first time round, then deepening each cut a little on the second rotation, and continuing until you are at the right depth or (if earlier) the repetition drives you mad :lol:.
Andy
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Looks like your cutter is blunt or you've got the wrong cutting angles, you should use a high speed, the type of material will definatly make a diference, but a darn good try I've learnt something watching.
Cheers
Stew
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The teeth looked pushed out rather than cut?
I know you wanted to make the cutting tool, but it might be a good idea to buy one to start with.
Would eliminate one possible problem and allow you to master the actual setup and process.
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edit: sorry, will repost later, daughter just hit the keyboard and deleted entire message :doh:
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OK - I totally agree, the teeth gaps look pushed out rather than cut out. I think I`ve made a huge error as I aligned the cutter and wheel on the x-axis and then fed the wheel straight into the cutter on the Y-axis. Consequently, is this not simply pusing out the groove rather than using the cutting angle and cutting it out or have I done it right? I appreciate the tool may not be to correct size for module .8 cutter but in terms of the cutting angles and rake, the tool looks fine and is sharp. Have I been cutting with it incorrectly? In my mind, thinking about it now, I`ve been "hitting" into the face of the brass with the face of the cutter rather than using the cuting edges, no?
(http://www.raynerd.co.uk/images/wheel.JPG)
Chris
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A quick search on Google under "clock wheel cutting" or "clock gear cutting" will help. Yhere's also vid's on doing this.
Bernd
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If you do find any links Bernd that will help then please post them. I can do a google search myself and have done many but none seem to be specific to my issues and setup. I have spent hours and hours, if not days searching for clock wheel cutting over the last months as well as aquiring many books and emails containing specific scans of pages of books. Research is not lacking, it is understanding.
Would appreciate any video links - haven`t found many of use.
This is an escape wheel but he feeds in the Y-axis as I did:
This feeds into the X axis:
&feature=related
Chris
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Research is not lacking, it is understanding.
Chris
Well then practice, practice till you get it right. With all that information that you've gathered it's going to take some time till you get the "knack" of cutting clock wheels. Rome wasn't built in a day, right?
Bernd
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I`m a bit lost with what your saying Bernd :poke:- I am practicing hence the wheel I`ve cut and all the information I`ve posted in this thread. No point going hell for leather at another wheel and wasting more brass without asking for advice as to where I could have gone wrong?
Anyway .....
I`ve just been speaking to someone who is a clock repairer and although he agrees that I have had issues with either the profile or height setup of my cutter (and so the wonky teeth) he said that the problem with my cutting is down to the brass I have used, apparently it is "sticky" plate brass- NBG and I need to use engraving quality leaded brass and cut in one pass. Now I need to order some spare cz120 brass!
Chris
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It looks like you have a few noticeable problems.
Your metal must be some sort of soft brass alloy, it surely isn't the hardened brass that a wheel of this type would be made of.
Your cutter is either blunt or doesn't have the correct clearance angles on it. As brass can usually get away with zero top rake, I would definitely suspect it being blunt. It needs to be honed to an edge that you could shave with.
On the first vid, it seems as though he is plunge cutting, but I suspect he is actually feeding the cutter in on the X axis as well, and only putting the cut on the Y. It is very difficult to see as the X axis movement would be very small. If you notice, he took well over a couple of minutes to cut the tooth. It has to be done slow and steady just as he showed. So for a 30 tooth gearwheel, over an hour to cut.
With regards to tooth positions, it looks almost certain that your blank or arbor has moved somewhat, due to cutting pressures.
Bogs
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John, really appreciate the reply. I didn`t realise that it should be that sharp, I thought sharp was just a clean front edge! How would I achieve such a sharp edge .... people talk about having sharp HSS lathe tools and it is the same there, I thought it just means a good clean cutting edge.
Regarding the process of taking the cut, I`ve spoken to a few people tonight and believe the best way to do this is to feed along the X-axis and take the entire cut very slowly but in one pass. This is the information I was given and I hope that Jim doesn`t mind me passing this information on:
Reading the information I have been given on here and in the message below, I think I have fallen on a few accounts...
Chris,
Really nice job of documentation on your blog. And congratulations on your first wheel, be it a bit less than perfect. I don’t think my first one was perfect either.
To your questions, I have cut many hundreds of wheels and pinions, so I will comment on what works for me and my thoughts as to where you may have gone a bit wrong.
1. It looks to me as if you cutter is not really “sharp” as in really sharp - as john mentioned above
a. Is it very hard? If not, it will be difficult to sharpen and will give you ragged teeth like you are getting
2. I feed from the X axis into the cutter rotating into the gear blank
a. I cut full depth in a single pass (if and when I measured it well and set it up properly)
3. I use coolant/lubrication . I realize there are many books that say it is not necessary, I think a lot of writers have not cut very many gears. Yes it is messy.
4. I suspect you may not have a “free machining” brass. Some brass formulations cut far better than others. I use ½ hard engraving brass for all my work and have for a very long time. I have tried some surplus brass that originated in China that was nearly impossible to machine, just FYI, even with coolant /lube and sharp cutters
5. Both wheel and pinion cutting likes a very rigid mount for both the blank and the cutter
6. I back up my blanks with either scrap aluminum or brass
7. I use fly cutters only as a last resort, but they work fine when the other 6 points above are in order
8. Cutter speed for fly cutting should be fast….. it is hard to rotate the cutter too fast on most mills…..I would push for at least 1500 rpm minimally
9. Feed rate should be slow into the cutter
Quite scary actually - reading all the above I think I have issues or done things incorrectly in nearly all aspects.
Time to try again....
Chris
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At a push, you can get away with a fine oilstone, they sell them on markets for a couple of squid, rough on one side, fine on the other. Forget about the side faces, you should flat the front face, the one that hits the work first, that should sharpen up all cutting edges. For lathe tools, you sharpen using the top face. It doesn't take long at all, you will soon see when the face has a chrome like finish, and you are liable to cut yourself on the edges. Then you know you have a sharp tool.
I actually use an Arkansas wetstone because it has a much finer grain structure than oilstones, and gives a super sharp cutting edge. Diamond laps can be used on HSS, and even with lots of water as lubrication, it will tend to clog up and ruin the lap. I keep those for putting a keen edge on carbide. Do not use the diamond laps with holes in, they are really useless for the size of tools we use.
Bogs
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Just been looking at commerical cycloidal form wheel cutters, as Darren said although a cost it would allow me to concentrate on setup and relieve some of the issues with the cutter. I thought I only needed two cutters, 0.6 and 0.8 mod as these are the only ones mentioned in my plans. The cheapest I can find, including postage are P. P. Thornton and they are £52 per cutter for mod 1 and below!
Too much for me to spend on two cutters.
Then I researched into a little more and discovered that in actual fact, the cutters are for 20 teeth and over and I would also need an individial 0.8 and 0.6 cutters for the pinions as these are 10 leaf and below! It would cost £208 on cutters alone. I`m acutally going to convert the pinions to lantern pinions so I won`t need cutters for this but £104 is still too expensive for two cutters that will be used only a few times. I`m going to have to work on my profile of my cutter! It did do the job, I`ll try and make another I think and take my time.
I was quite excited when I noticed RDG sold cutters for £18.50 but then noticed they were involute cutters and not cyloidal ... since all books I have read discuss cyloidal I guess the involute system will not be suitable.
Chris
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(http://www.raynerd.co.uk/images/wheel2.JPG)
Tooth form looks quite good so far!
Look at the first tooth and how bent it is ... obviously it is the furthest one away from the current cut in the next photo:
(http://www.raynerd.co.uk/images/wheel3.JPG)
Any thoughts.....?
In the first pic above the tool looks bent as if it bowed under hardening, may be the angle but if you didn't recheck centre then that will account for the leaning teeth.
In the second pic you don't have enough clearance on the cutter, not the brass smear marks behind the cutting edge, tool is nowhere near sharp enough.
If making silver steel cutters for brass or wood harden out to cherry read and quench, preferably water as oil isn't a sharp enough quench and the heat inside the cutter can cause it to temper at the same time as it transfers to the edge.
Then contrary to what you read don't temper. Brass and wood cutters can run at a higher hardness than ones for steel as it's a softer material.
The face grinding operation will actually put enough heat into the material to temper it slightly.
If you temper to what the books say the grind you actually reduce the temper, believe me brass and wood are far better at higher hardness's.
Wood is no good as a backing, far too soft, try alloy but remember to lubricate it with a drop of paraffin or WD40.
John S.
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Cheers John, I`ve just this second come back in from cutting out two more blank wheel cutter disks. You are spot on, the wheel cutter seems to have bowed out - it is soft and not sharp and this was NOT silver steel. I have cut my new blanks from silver steel guage plate that was advertised as "suitable for hardening for tool steel". I`ve also done a little test, filed a little edge of a scrap piece then heated to cherry and quenched, then tried to re-file it. It was 100% significantly harder but my file could still dig in a little. Is this still right, even after hardening should I be able to file it a little, i.e make a mark? I don`t want to spend hours making a cutter and then find out that I can`t harden it again. How long do I need to hold the piece at cherry red before quenching?
I appreciate your advice regarding not needing to tempter the steel - I will try the cutter without tempring.
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No once hardened a file should skid off it.
Get it bright red, hold it there for a couple of minutes and drop into a can of cold water and leave.
Then try that.
John S.
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Cherries vary in shade. In one of his books, L C Mason said it was better to go beyond most cherries to the colour of boiled carrots, where orange is beginning to creep in. That seems to work for me.
Andy
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Chris,
I think you have all the answers now, everybody has mentioned what I was going to say and I think you've started addressing the issues. Just to summarise incase people miss anything:
Firstly, you know the profile of your cutter should be right as you profiled it cylindrically and sectioned it. As you said, it didn't look like silver steel so it's too soft. Only the 2 Johns picked up on the fact that it has infact no clearance angle, because it's made from round, the work piece is actually tangential to it when it's cutting and as John S said, that's why you can see brass pick up on it. This and a combination of soft brass and not being sharp enough has to be why it's not cutting properly and bending the material.
The only way the angles can be out is if your tramming is out (unlikely) or you didn't get back to centre height.
As Bogs said, the guy that feeds on the Y axis must also feed a little each way on X too, otherwise he'd have a radiused bottom to his teeth (however small that may be as it's very thin). So you might as well set the depth of cut and just feed on X.
Excellent thread, well done, good first attempt - keep up the good work. You've gone onto another level now and are certainly carrying out more complex machining than I am.
Nick
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One more thing about hardening the cutter. I've read magazines that call for hardening a piece that a magnet is used to tell when the part is ready for quenching. The part you are heating will no longer hold the magnet. This does not mean to leave the magnet on the part as you heat it but getting close with the magnet untill it doesn't attract the part anymore. Then drop it in your quenching medium.
The part should actually be swished around in the quenching medium due to pockets of vapor forming near the heated part, thus insulating it from the quench meduim. This causes certain sections to be harder than others.
Good luck on making your new cutters. Hope you have success this time around and above all take your time.
Bernd
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Bernd
Called the 'Curie Point'.
http://www.britannica.com/facts/5/622880/Curie-point-as-discussed-in-steel-metallurgy
Lots of other sites to search the subject if you like long words ..
Dave BC
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Dave,
I remember it as the CURRY point.
RED HOT a**e, when you lose your grip on things.
Bogs
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Just regarding the clearence on the cutter as John mentioned earlier. I totally understand what you are saying, your saying that the bottom edge is following through into the work but John Sheadle doesn`t mention doing anything to change this on his plans, infact since the mounting point is off-set there should naturally be clearence on this bottom edge. I wonder what I could have done wrong?:
(http://www.raynerd.co.uk/images/shadle.jpg)
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Dave,
I remember it as the CURRY point.
RED HOT a**e, when you lose your grip on things.
Bogs
:lol: :lol:
Not keen on curries now ... Ricky Nelson did a song about 'em years ago ...
'Hello Vindaloo, Goodbye A**e' ..
Or similar .. memory fades ..
Bit :offtopic: ain't it?
Dave BC
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I thought it was Johnny Cash:
"and it burns, burns, burns, burns
the ring of fire, the ring of fire, the ring of fire"
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Chris
Your adventures with gear cutting have been very interesting, at some point in the future I'll be attempting a clock, and I've been putting a lot of thought into making the tooling, that is one of the reasons I made the tool post grinder, I'm not going to give away too much about my ideas as I'm still working them up, and they may end up in a complete disaster, but if they work out I'll end up with cutters of the same module you are after, that you can have the use of with pleasure, but you'll have to wait a while .
I've though of using lantern pinion that can be made without a special cutter, but if you do this you have to be carful that you've enough room in the gear train to fit the bigger lanterns, I've also read than lantern pinions work better with a wheel with a slimmer tooth form.
Have fun
Stew
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Stew, I`m intregued and can`t wait for you to make a start. If I have limited success with my own cutters, I may come crying to you to borrow some! Will yours be made from toolsteel and multi-tooth? If so, then you`ll be able to stick to normal pinions rather than lanterns. Regarding the lanterns the info I have been given it to use the circle through the center of the trundles (wires) as the pitch circle and make the wires 1.25 x module in diameter.
I`ve pretty much posted everything up here but a more concise account of my progress is here:
http://clockbuilding.blogspot.com/
I`m actually managed to speak to a few clockbuilders over the last few days and although they have pretty much said everything that has been mentioned here, they have really stressed the need to use engravers brass and not sticky "normal" brass. Although I appreciate I had many issues I do believe some of it was due to the type of brass. They all explained that sticky brass tends to bend and push out rather than cut out as flakes.
Stew, have you decided what clock you are attempting? I do so hope it is the same as my selection, I think I remember seeing it at your house, that way I`ll be able to watch your progress log and directly relate it to my build, there is no doubt I`ll get stuck at certain areas. I have purchased the plans and paid quite a lot of money for the plate brass for Colin Thorne's Skeleton Timepiece.
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I've though of using lantern pinion that can be made without a special cutter, but if you do this you have to be carful that you've enough room in the gear train to fit the bigger lanterns.
Stew, considered this also but got told that since all wheels need depthing out to scribe onto the frame, the small adjustments needed by lanterns would hardly be noticed. Only what I got told.
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Chris
I've got ideas to make a multi tooth pinion cutter.
As for the clock all I've decided is that it will be a skeleton clock.
I'm still very much getting the kit around me before i make a start, I also want to get a couple of other projects done and I want to complete the lubricator and boiler feed pump for my loco first, so I guess I wont be making a start until the new year.
Stew
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I know it's for involute cutters but here's an article I wrote many years ago.
http://www.metalwebnews.com/howto/gear/gear1.html
John S.
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I've bee reading your page recently John, picked up quite a bit from it .. :coffee:
Thanks for writing and making it available :beer:
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Chris,
Even though it is offset, imagine if you could zoom right in on the cutting edge, the clearance angle on the bottom edge is tiny, it's still almost tangential since it is a radius so some rubbing will occur, why not grind a straight line clearance between each end of that arc, then you know you've got a decent clearance angle.
Nick
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OK, well I`ve set off on the next attempt at the cutter. I have decided a few things since my last attempt.
1. Use the correct material, a suitable carbon steel and ideally heat treat a piece to test it.
2. I need to be more accurate. I did some more calculations and the difference between module cutters is tiny, clearly I need more precision.
3. I need to really sharpen the cutter.
So with that in mind I decided to dig out my mitutoyo calipers and guage vernier that was given to me from a bloke at work a few weeks ago. I haven`t used them yet and I think now is the time to learn. It puts me off because they are imperial but I`m getting much better now switching between metric and imperial over the last few months of reading both.
(http://www.raynerd.co.uk/images/cuttere1.JPG)
For the material I ordered some guage plate or ground flat stock as John Shadle suggests in his plans. Whats more, it acutally was advertised as "suitable for hardening for tooling".
(http://www.raynerd.co.uk/images/cuttere2.JPG)
I next cut the out a rough disk with the hacksaw. Drilled a hole in the centre and mounted it on the actual arbour that it will be situated on when the cutter is finished. I then trued it up in the lathe and immediately hit problems. This stuff is pretty hard! I remembered a conversation we had on here a few days ago with John (Bogs) and remembered about honing in with a stone on the cutting tip. What a difference it made, the steel started curling and shaving off. I then continued cutting in from both sides, skimming slithers off until eventually I got to a width of .05" for the tooth tip or what will become the gap between teeth. I then took this down to the correct depth for the dedendum of the teeth.
(http://www.raynerd.co.uk/images/cuttere3.JPG)
Next I needed to put on the radius 2.5mm. I really wanted to find a more accurate way of doing this but couldn`t think of anything better than John Shadle suggests in the plans. A well if it is good enough there it is good enough for me. I rounded an old 2.5mm drill bit to profile and mounted this in a little holder I made and held it with a grub screw:
(http://www.raynerd.co.uk/images/cuttere4.JPG)
I mounted this in the tool post and run the lathe on very slow with lots of oil. I thought I`d hit problems but to my astonishment, the steel started peeling off! I continued until I got to depth for the addendum and removed it all from the chuck:
(http://www.raynerd.co.uk/images/cuttere5.JPG)
If you look at the top of the picture below you can see the nice radius profile on the cutter. It looks much better than my previous attempts - much better
(http://www.raynerd.co.uk/images/cuttere6.JPG)
.... and then the battery went on the camera!
I`ve not done too much more other than remove it from the arbour and litterally cut the disk in half with a hack saw. I have then taken my time and really sharpened and honed in on the cutter edge. It is now really sharp and shiney. The great thing about this method is that you actually end up with two cutters (each half of the disk) and if an offset hole is drilled on both sides of the half disks, you end up with two cutting sides on both halfs of the cutter. John Shadle says this method takes an hour and I`ve probably put a good two hours already but I`m nearly there. I really hope this works otherwise I`m going to be pestering Stew to get this tool post grinder wheel cutting idea up and running :whip: lol.
I`ll take more pictures tomorrow, hopefully of a finished cutter.
:wave:
Chris
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Have you seen this one Chris?
http://images.google.co.uk/imgres?imgurl=http://lesgrenz.homestead.com/files/Testing_the_Broach_fs.jpg&imgrefurl=http://lesgrenz.homestead.com/horology.html&usg=__f5sKa7dZKWZfRueXmSv5g5KpcRI=&h=480&w=640&sz=44&hl=en&start=190&sig2=pHSAYOZa_kE81JN0Tk-yZA&um=1&tbnid=a8fdc4_9xLn88M:&tbnh=103&tbnw=137&prev=/images%3Fq%3Drotary%2Bbroach%26ndsp%3D18%26hl%3Den%26safe%3Doff%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-GB:official%26sa%3DN%26start%3D180%26um%3D1&ei=NszwSuveH8yvjAf93ozJCA
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I checked out the rest of his web site. Very nice. He's got some nice machines.
Bernd
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At last Chris,
You are starting to settle down, rather than jumping in with both boots on and making a balls of it.
Take your time and inwardly digest everything that you read and are told about.
Everything you require is at your fingertips, and if you follow it, rather than going off at a tangent to try your own thing first, you will have success.
You can play about later, after you have got the basic scalps hanging from your belt (or lathe tool).
Because you are making a clock, you will have plenty of time in the future for experimentation. :lol:
Bogs
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Darren - yes I have come accross his website and it has quite a few nice tips. I need to do a post in resources at some point, as much for my own good, with a collection of all these clock related websites. I`ve stupidly not been saving them to my favourates.
Bogs - You are starting to settle down, rather than jumping in with both boots on and making a balls of it.
, yes I`ve been too eager to see the outcome. I figure that if I really am going to make this, then time isn`t something I should be worrying about (excuse the irony of the pun!)
Chris
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I was over on PP Thornton website and it got me thinking:
(http://www.ppthornton.com/images/homepage_08.jpg)
(http://www.clock-works.clara.net/cata/catimage/CATCUT1t.jpg)
If I took my time and ground a similar profile on it, could I not turn my blank into a multi tooth:
(http://www.raynerd.co.uk/images/cuttere5.JPG)
Obviously I would have to take some material of the back edge of each, as it would be central mounted and therefore the relief would be need to be cut into each "tooth".
Am I missing something?
Chris
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If I remember right. Cutters like those are cut on a relieving lathe. The cross slide runs on a cam that makes the tool cut the relieve as the cutter revoles. That's about the least complicated way of explainging it.
Got the pics you wanted posted in the clock thread I started.
Bernd
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Am I missing something?
Time and experience I suspect, that's what your paying for by buying one of their cutters, if you believe you can match their product then go for it .........
One reason for buying the cutter is .......... you can, ......... One reasons for making your own is ....... you believe you can, finances obviously come into the equation too ...... whatever you choose. good luck and enjoy the ride.
CC
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Bernd got it spot on, a long time ago I used one of those lathes along with a grinder that did a similar job.
Having said that there is another way to do a multi tooth cutter with an off set mandrel, but your too far into the job now to do it.
Have fun
Stew
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Cheers guys, yes, I`m going to stick with this for now - it is working so I don`t know why I`m considering changing anything! I guess I was just curious. I have been speaking to someone lately who simply grinds the profile out of a piece if square tool steel and locks it into a fly cutter! That must take a steady hand on the grinder, the profile is tiny!
Anyway, just got in from the shop from making a pillar.... I`ve actually started :dremel: :clap: I guessed I could start on some of the other parts while I figure out this gear cutting!