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Making a pinion with a fly cutter

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Chris TickTock20/09/2020 13:31:34
576 forum posts
41 photos

In order not to attempt walking in to many directions at the same time i am sticking with but paying close attention to detail of the single point cutter.

I am wondering if a M42 end mill will cut a radius on HSS steel on my Sherline mill. HSS steel simplifies things as I believe it has the same hardness as hardened silver steel and gauge plate.

Whilst there seems a consensus of speed between 200 to a max 500 I am yet to understand if too slow a feed rate can cause issues, obviously too fast feed could.

Chris

Michael Gilligan20/09/2020 14:13:24
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16342 forum posts
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Posted by John Haine on 20/09/2020 12:04:47:

.

Quite right Michael, but the multi-tooth cutter is better balanced and maybe not so critical on feed rate as there's always a temptation to feed too fast.

.

We’re both right ... All is well : There is peace and harmony yes

MichaelG.

John Haine20/09/2020 14:21:44
3320 forum posts
176 photos

M42 is HSS. You need carbide to cut HSS. Your mill may not have the rigidity to do this, but try it.

With too slow a feed rate a cutter rubs and looses its edge.

Considering that many people have made single point and multi-tooth cutters from gauge plate and successfully cut pinions with them I suggest to stick with it rather than introducing another challenge, machining HSS!

It has often been said that carbon steel (silver steel or gauge plate) can be harder and take a better edge than HSS, but HSS has the ability to cut at a high speed without softening.

Chris TickTock20/09/2020 14:53:44
576 forum posts
41 photos
Posted by John Haine on 20/09/2020 14:21:44:

M42 is HSS. You need carbide to cut HSS. Your mill may not have the rigidity to do this, but try it.

With too slow a feed rate a cutter rubs and looses its edge.

Considering that many people have made single point and multi-tooth cutters from gauge plate and successfully cut pinions with them I suggest to stick with it rather than introducing another challenge, machining HSS!

It has often been said that carbon steel (silver steel or gauge plate) can be harder and take a better edge than HSS, but HSS has the ability to cut at a high speed without softening.

Your right John on all counts. Looking at everything it might be the case I heated to orange as opposed to red whilst hardening. What are the effects of over heating by this margin, possibly 100 degrees C above. In future only remedy is reducing light. All these small points add up.

Chris

Chris TickTock21/09/2020 14:55:05
576 forum posts
41 photos

Update after re think

I think it might be beneficial for me to post my thoughts after attempting and succeeding cutting a pinion.

Firstly it is not easy, take your eye off the ball and you will readily cock it up.

Secondly the method I used was given to me by Jerry Kieffer an American horologist and craftsman, some folk despise his machinist stance others like me admire him. Jerry has always been patient and polite and I respect him as I do to all who post with good intent. Having said that Jerry is really patient and kind to give advise but you have to learn to use your machinary well and think for your self at the end of the day.

This was a good example of a relative greenhorn taking on a fairly difficult task. I cocked up many ways until i thought why. The main reason was lack of experience and yes...tiredness.

Thirdly I have looked at alternative ways of making a pinion and in particular Mike Crossfield has been very kind in helping out on this. As far as I can best fathom from looking at Mike's way there are different ways to achieve the same outcome and I cannot see why one is superior to the other. Mikes cutter will possibly reduce vibration so will be something for me to try when I have a few spare hours to compare.

Anyway I have attached a photo of my first, second and third attempt. The third when polished up would work, is a fair product but will hopefully get better with a tweek here and there in future.

Regards to all

Chris3 stages pinions.jpg

 

Edited By Chris TickTock on 21/09/2020 14:55:38

SillyOldDuffer21/09/2020 16:41:51
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6309 forum posts
1380 photos

Posted by Chris TickTock on 21/09/2020 14:55:05:

...

Anyway I have attached a photo of my first, second and third attempt. The third when polished up would work, is a fair product but will hopefully get better with a tweek here and there in future.

...3 stages pinions.jpg

If your No 1 were my first attempt I'd be pleased with it. Although I've picked up several tricks since retiring into Model Engineering, tackling a pinion like that would be a new challenge for me and highly likely to go wrong.

Expectation management is all part of the game. Sooper-dooper equipment and materials with a dash of good advice doesn't guarantee instant success; we have to develop skills. And recognise it takes time and they're unlikely to develop in a straight line. Not uncommon for second attempts to take a step back, and for number 3 or 4 to leapfrog ahead. Or for skills to plateau before improving again.

Main thing is to not be discouraged by poor results: take a break, ponder the problem, and try again.

Dave

Chris TickTock21/09/2020 16:51:50
576 forum posts
41 photos
Posted by SillyOldDuffer on 21/09/2020 16:41:51:

Posted by Chris TickTock on 21/09/2020 14:55:05:

...

Anyway I have attached a photo of my first, second and third attempt. The third when polished up would work, is a fair product but will hopefully get better with a tweek here and there in future.

...3 stages pinions.jpg

If your No 1 were my first attempt I'd be pleased with it. Although I've picked up several tricks since retiring into Model Engineering, tackling a pinion like that would be a new challenge for me and highly likely to go wrong.

Expectation management is all part of the game. Sooper-dooper equipment and materials with a dash of good advice doesn't guarantee instant success; we have to develop skills. And recognise it takes time and they're unlikely to develop in a straight line. Not uncommon for second attempts to take a step back, and for number 3 or 4 to leapfrog ahead. Or for skills to plateau before improving again.

Main thing is to not be discouraged by poor results: take a break, ponder the problem, and try again.

Dave

Dave,

Wise words 'expectation management', I expected it to be easier than it was. Of course it will become so with practice, providing I learn.

chris

Dave S21/09/2020 19:15:51
53 forum posts

If you are losing the edge on your cutter rapidly that suggests either the heat treat was not good or you are running it too hard and this drawing the temper, which leads to softening, which then rubs and heats and so on in an unfortunate feedback loop. Are you using cutting oil? How fast are you turning the tool and what feed rate?

My silver steel cutters were a bit hit and miss until I bought an enamelling kiln. I didn’t buy it for heat treating, but it goes hot enough, is pretty well controlled on the temperature and is convenient as it’s in the workshop anyway.
Since I started to use it for heat treat my hardened parts have been much better and more consistent. Not suggesting you need a heat treat oven, but judging temperature by eye on a scaled up piece in a flame is not a thing I ever mastered...

Coventry Grinders sell quality Silver steel at reasonable price.

Dave

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