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Gearotic for clock wheels?

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Peter Bell30/05/2011 19:55:45
399 forum posts
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Just dowloaded the very impressive Gearotic and amongst other things I see it will do clock wheels even down to smallish sizes ie 0.6M.
 
At this sort of module it quotes a min milling cutter size of around 0.75mm
 
Question is has anyone used Gearotic to produce clock wheels in brass of this sort of module?
 
Thanks Peter
John Stevenson30/05/2011 20:27:22
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Peter, smallest I have done with Gearotic is 1 mod, turned out good, never tried finer as I don't use small cutters. Sorry can't be of more help but the program does work well.
 
John S.
Pat30/05/2011 20:50:44
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I have used Gear Wheel Designer a similar program but limited to circular gears. For a 0.6 module tooth you need an end mill less than 1mm diameter for a 60 tooth wheel and 0.4 mm diameter for the pinions. This is getting very fragile for the average milling exercise. Yes it is possible to use a slitting saw and the appropriate milling path which is getting near to using the conventional profile cutters traditionally used by clock makers. The surface finish is all important and there is a lot of polishing to be done after milling teeth compared to using a profile cutter.
 
Hope this helps by putting numbers on the end mill diameter. Regards _ Pat
Peter Bell31/05/2011 08:24:24
399 forum posts
167 photos

Thanks John & Pat for the replies and putting the numbers against the modules.
 
That Gear Wheel Designer also looks impressive.
 
Never thought about a slitting saw for the smaller sizes, when you say lot of polishing, is the finish really bad using a slitting saw?
 
Regards Peter
Pat01/06/2011 02:46:40
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In a single word yes. The problem is with the ridges caused by the slitting saw as it moves to traverse the tooth profile using the 4th axis.  I have done this on a large pinion but resorted to a fine file to make it run (20 teeth some 75mm diameter from memory).  You might have luck grinding the profile of the slitting saw to suit the gap between the teeth. Small slitting saws are cheap and if the edges are well ground then polished to match the gap between teeth then it might be a very good tool - possibly as good as module cutter. May be some one has tried this on clock gears and with luck will respond.   What I am talking about is thinning each side of the saw keeping the manufactured rake and tip clearances.  The modified saw would then rub on the sides and if the tool is well polished should leave a nice finish as clock wheels are high leaded brass.  Gashing of the teeth is often done to save the delicate fly cutter from roughing out as well as finish cutting. However this may also be a rigidity issue with fly cutting wheel cutters.
 
Regards - Pat

Edited By Pat on 01/06/2011 02:51:53

Edited By Pat on 01/06/2011 02:53:33

John Stevenson01/06/2011 07:01:38
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5068 forum posts
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Peter,
At the risk of setting various people off again were you going to use CNC to cut these pinions as that is what Gearotic is aimed at ?

John S.
Peter Bell01/06/2011 08:11:55
399 forum posts
167 photos
John & Pat
 
It just looks such a good neat solution I wondered just how feasible it is really. I have a selection of wheel/pinion cutters but somehow you never seem to have the right combination.
 
I want to make some 0.75m & 0.6m 112t wheels in brass and matching 12t pinions in mild steel. I see that a 0.6 12t pinion is quoted as needing a max mill dia of 0.6842---is that feasible---sounds a very small end mill to me!
 
Hope to get the 4th axis soon---you may have been working on it John (I hope!)
 
Pat,
 
Asked Gear wheel desiger the question about the 0.6m wheel and got the following reply.
"There is no problem making these gears but the software only supports the use of an end mill"
 
Thanks Peter
 
 
John Stevenson01/06/2011 20:54:32
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Peter,
 
4th axis being worked on at the moment..
 
One option that is being looked at in Gearotic is the ability for Gearotic to make it's own cutter to suit any profile.
 
It goes a bit against what it was designed for, i.e.using an off the shelf end mill, but will allow a cutter to be made to suit the smaller pitches.
 
Not written in stone yet but the idea is to take a silver steel blank and in the 4th axis mill a flat on to just above the centre line, then rotate 180 degrees and mill a second flat to form a spade bit.
 
Then rotate 10 degrees or so and mill the involute shape down one side, rotate 180 and repeat.
 
The 10 degree angle will give side relief. Then the cutter is hardened and tempered.
 
Cutting from then on is simple in that it's only feed to depth and pass thru the blank, index and repeat.
 
In fact if you can get someone who is CNC equipped to make the cutter the gear could be cut by all manual means with dividing head etc.
 
At the moment Art is working on sorting the bevel gear cutting code out and I'm hoping the cutter will be addressed later.
It can be done at the moment but you have to do it by various moves but hopefully later the whole process will be automated so you just fill boxes in and the code is generated to do the cutter.
 
John S.
Peter Bell01/06/2011 22:02:21
399 forum posts
167 photos

John,
 
Thanks for the good news all round.
 
I think that I had read about Gearotic making cutters somewhere else, it all sounds a bit too good to be true really but it would certainly help for the 0.35 wheels I need to cut. As I do not need them immediatly it may be ready in time.
 
Made single point cutters before by trial and error to match antique wheel with great success and look forward to receiving the 4th Axis
 
Peter
John Stevenson01/06/2011 22:48:17
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5068 forum posts
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Peter,
If it's not give me a shout and I can code it up longhand just for the one cutter.
 
John S.

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