Material Recommendation

Hi,
For a variety of reasons I want to make my own (very small) gear cutters.
I have little facility for hardening so hope that it might be possible
to simply heat the pre-machined cutters to 'cherry red' and water quench
prior to final profile grinding.
What I would like from the group is a recommendation with regard to the
material I should use to make the cutters. I have seen Silver Steel
available up to about 20mm dia but my preferred size would be between 25
& 30mm.
TIA.
JG
Reply to
JG
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Silver Steel is readily available off the shelf up to 40mm, after that it's special order.
What sizes [ dia ], widths, qty etc are you looking for. Must have some offcuts around here somewhere.
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Regards,
John Stevenson Nottingham, England.
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Reply to
John Stevenson
John Stevenson said
I've not looked in the right place then :)
I need to make Cutter Nos. 1, 2, 3, 5, 6 & 7, they need to be 3mm finished thickness and ideally 30mm dia. If you do have suitable offcuts I would be grateful for the opportunity to purchase same - probably enough to make two 'sets'.
Very useful John. Some of it I am already familiar with but there are some 'gems' there so it is now printing . . . . printed.
It is my intention to 'generate' the correct involute at 5 times size and use the pantograph I've built to dress the grinding wheel to the profile. As I said before these are very small gears at 0.25 Mod - the smallest will be 4.5mm OD - 16 tooth, the majority 40 tooth 10.5mm OD and one 620tooth 155.5mm OD. As they will all be brass I'm hoping that I'll get away with no 'relief' since the 'land' on a 30mm dia cutter (six flute) will be less than 3mm. Your advice on this aspect would be most appreciated.
JG
Reply to
JG
From page 31 of latest J&L flyer:
Silver Steel 30mm x 500mm 10:80ukp 1 1/4" x 13" 12:35ukp
Reply to
Neil Barnes
I'll have a look tomorrow but I'm certain I have plenty of 30mm in stock.
Those are small, they translate to 101.6DP for imperial sizes. I presume you say you will grind each side up with a profiled wheel ? as with a tooth space this small you wont be able to get inside.
No relief in brass will be OK but back off as much as you can. Top off at an angle to leave about 1mm land.
Machine up in silver steel and harden out. Don't temper, leave hard. The reason for this is brass needs a fine edge and it's soft enough not to shatter the tooth. Added to this the amount of heat generated by the face grinding process to sharpen the cutter after hardening will be enough to drop the temper just a tad.
I found this out making special form cutters for hardwoods. If I tempered down to straw colour by the time we had reground a couple of times we couldn't keep an edge.
There is a program on the internet called Geargen, do a web search for it. It's shareware but no longer supported and fortunately it's not crippled. Old DOS program, download this and select your pressure angle 20 or 14-1/2 [ no other choices in this program] enter the number of teeth and the DP which in this case is 0.25 mod x 5 converted to DP = 20.32
Generate gear then go into plot and select gear 1 and hen you have a choice on saving as a DXF file either 1 tooth, 1 space or the whole gear. This will give you a geometrically correct tooth / space form at fives time the size. You need to do this for each tooth count
-- Regards,
John Stevenson Nottingham, England.
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Reply to
John Stevenson
I make mine from old files. Heat the file red hot, and cool very slowly. It machines like the proverbial butter!
Steve R.
Reply to
Steve R.

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