‘Reverse Engineering’ a Gear.

[John CParticipant @johnc47954]

I would like to try to cut a gear like this:

It is a chuck key for a 'MultiSize' Collet chuck. Working through the various books on gears I can't find a way to identify the properties of this gear from scratch. The dimensions are:

Without knowing the pressure angle, tooth form or modulus I am in the dark as to how to find a cutter! I know I could grind a single point cutter 'by eye' but i would like to try to work out the properties as a learning exercise. Any suggestions gratefully received.

Many thanks,

John

p.s. I would also like to reverse engineer the thread title to get the spelling right!

Edited By John C on 16/09/2016 14:46:25

[John CParticipant @johnc47954]

[Martin KyteParticipant @martinkyte99762]

You could start off with plasticine to get the tooth profile.

Martin

[John CParticipant @johnc47954]

Thanks Martin,

But wouldn't I just end up with a mirror image of the teeth….which is just like the teeth themselves……

Thanks,

John

[Brian HParticipant @brianh50089]

You could use the plasticine to create a mould into which you could pour some of the cold casting resin available from Ruberts Ltd or any other suitable casting resin.

[duncan webster 1Participant @duncanwebster1]

Wouldn't it be easier to go down your local engineers merchant and riffle through their box of unidentified chick keys until you find one?

[Michael GilliganParticipant @michaelgilligan61133]

Posted by duncan webster on 16/09/2016 18:33:06:

Wouldn't it be easier to go down your local engineers merchant and riffle through their box of unidentified chick keys until you find one?

.

Hypothetically possible; but rather unlikely, methinks.

The key in question is, I believe, shown here: **LINK**

http://www.gandmtools.co.uk/shop/burnerd-multisize-collet-chuck-collets-key-lo-fitting-80202464/

MichaelG.

[Anonymous]

Having looked at my Multisize collet key by Jacobs, and a Jacobs chuck key, I think that only in a loose sense are they gears. The collet key bears a passing relationship to a bevel gear, but it looks like it has been cut in one pass, so cannot be a true bevel gear. The mating gear teeth also seem too pointed to be a bevel gear. I expect they have been designed for ease of engagement, and simplicity of manufacture, rather than as gears per se.

Searching for the precise gear parameters is probably a lost cause as I doubt they were designed using those parameters in the first place. If the intention is just to create a useable key filing would be as good as any method.

Andrew

[frank brownParticipant @frankbrown22225]

I think that the secret is the number of teeth (11/13?). I found an obscure chuck key this way in some modern catalogue in a builders merchants in the Yorkshire Dale !! I suspect the web might have a wider choice.

Frank

[Michael GilliganParticipant @michaelgilligan61133]

Posted by John C on 16/09/2016 14:44:42:

The dimensions are:

.

12 ^^^

[MuzzerParticipant @muzzer]

Posted by Andrew Johnston on 16/09/2016 18:54:33:

……it looks like it has been cut in one pass…

In which case, presumably the challenge (solution) is to make a cutter with a profile that fits the machined valleys as accurately as you can. Then make up a suitably shaped blank and present it so that you reproduce the valleys in the same positions. With a rotary table set to the correct position and angle, that should be reasonably straightforward, involving simple passes of the tool.

I've got a couple of these myself, so I understand they are not pocket-sized. But that cuts both ways and means that you should find it easier to measure up than a standard drill chuck key.

You must post pics so we can see how you get on. Good luck!

Presumably this should be made in high carbon steel so you can harden it.

Edited By Muzzer on 16/09/2016 20:42:13

[Nick HulmeParticipant @nickhulme30114]

I'd just take it to my local tool stockist and see what they had, it's highly likely you'll find a chuck key that just needs a larger or smaller diameter chunk sticking out the front and that's easy,

– Nick

[John CParticipant @johnc47954]

Thanks for all the replies. The intention is to make the thing as an exercise. I think the ground up bit may be the way forward. I was hoping for a way to deduce which conventional cutter profile would be appropriate.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Nick Hulme on 17/09/2016 01:21:10:

I'd just take it to my local tool stockist and see what they had, …

.

You must have a very good 'local tool stockist', Nick.

MichaelG.

[John CParticipant @johnc47954]

Success! Thanks for the ideas. All credit to John Stevenson for his idea of modifying Ivan Law's method of making gear cutters using tapered milling cutters. I picked up a carbide tapered cutter from JB tools which worked very well.

Here is the cutter, dimensions obtained by repeated trying of different milling cutter sizes and distance apart. This was tried by eye up against the teeth of the pattern gear. I settled on using an 8mm with 6mm between centres to leave a 2mm stub. I drilled an 8mm hole in a piece of scrap and marked the tapered cutter where it touched the edges of this hole. I then repeated the cutting process on gauge plate with the tapered cutter set to the height to form cutting edges. The gauge plate was hardened and tempered. The cutter was held in a slot cut in round bar so that the cutter face was on the centre of the bar.

The blank was cut with the taper set on the topslide. I cut this from one piece of bar, bored and loctited this this to the shaft. The dividing head was offset to the angle of the base of the teeth. I hogged out the bulk of the teeth with a 3mm slitting saw, then set the cutter to centre height and made several passes to get to depth. Thanks to 'gear cutting for the Shay' by Patrick Ackermann on uTube for a demo of cutting bevel gears.

The result:

And it works!

[Michael GilliganParticipant @michaelgilligan61133]

Nicely done, John

MichaelG.

[Brian WoodParticipant @brianwood45127]

Hello John,

​That sort of job can give immense satisfaction and reward far in excess of the humble task it does, as well as being a useful exercise for the grey matter. Nicely done; much more satisfying than ratting through boxes of similar looking chuck keys to find a match for it.

​Brian

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