Clock wheel cutter

[raynerd]

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

[Bernd]

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

[raynerd]

I`m a bit lost with what your saying Bernd  - 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

 

[bogstandard]

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

[raynerd]

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

[bogstandard]

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

[raynerd]

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

[John Stevenson]

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:




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.

[raynerd]

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.

[John Stevenson]

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.

[andyf]

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

[NickG]

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

[Bernd]

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

[Bluechip]

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

[bogstandard]

Dave,

I remember it as the CURRY point.

RED HOT a**e, when you lose your grip on things.


Bogs

[raynerd]

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?:

[Bluechip]

Dave,

I remember it as the CURRY point.

RED HOT a**e, when you lose your grip on things.


Bogs

  

Not keen on curries now ... Ricky Nelson did a song about 'em years ago ...

'Hello Vindaloo, Goodbye A**e' ..

Or similar .. memory fades ..

Bit  ain't it?

Dave BC

[raynerd]

I thought it was  Johnny Cash:

"and it burns, burns, burns, burns
the ring of fire, the ring of fire, the ring of fire"

[sbwhart]

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

[raynerd]

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.

[raynerd]

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.

[sbwhart]

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

[John Stevenson]

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.

[Darren]

I've bee reading your page recently John, picked up quite a bit from it ..   

Thanks for writing and making it available 

[NickG]

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