Clock wheel cutter

[raynerd]

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... 

Thanks... that really helped. I`ll let you know how it goes...

Chris

[bogstandard]

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

[John Rudd]

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.....

[raynerd]

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.

[raynerd]

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:







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.



..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:



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!



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




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


 

[75Plus]

Chris,

That bar is what I refer to as a "Linear Taper Remover"      (There is a story that goes with that name.)

Joe

[raynerd]

Did the trick anyway 

[sbwhart]

Making nice progress Chris    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

[raynerd]

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.

[NickG]

Looking really good Chris 

[raynerd]

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:


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.



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!



I also hardened the cutter this evening so tomorrow I really a ready to give it a whirl!

Chris

[NickG]

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

[Darren]

Looking good so far ... be interesting to see how this goes ...

[Stilldrillin]

Good luck Chris! 

[sbwhart]

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

[raynerd]

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!

[raynerd]

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



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:



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:



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.



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.



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...



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   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:



Then tidied it up a little more and now it looks like this:



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.....?

[raynerd]

Just reading back on my post, should I be feeding the wheel blank into the cutter on the X axis?

[Stilldrillin]

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! 

You need to rough out the profile, then go round again with a very sharp finishing tool.

My 2 pennorth...... 

David D

[andyf]

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 .

Andy

[sbwhart]

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

[Darren]

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.

[raynerd]

edit: sorry, will repost later, daughter just hit the keyboard and deleted entire message 

[raynerd]

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?



Chris   

[Bernd]

A quick search on Google under "clock wheel cutting" or "clock gear cutting" will help. Yhere's also vid's on doing this.

Bernd