Gear, Gauge, or Cutter ?

[Michael GilliganParticipant @michaelgilligan61133]

On a whim … I bought this yesterday :

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If nothing else, it will make a pretty paperweight !

It has the look of High Speed Steel, and there is a double ‘rake’ on the teeth … so it seems unlikely to be just a gear … so now I’m wondering if it might be a tool for shaping internal gears.

Any ideas ?

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

[Nigel Graham 2Participant @nigelgraham2]

It could indeed be a gear-shaper cutter though I'd have thought it would have a key-way or dowel holes in it to ensure the cutter and work-piece rotate correctly.

Alternatively as you question suggests, a master or calibration gear for a gear-measuring machine of some sort?

Elegant engraving!

[Pete.Participant @pete-2]

Looks like wear on the tip of the teeth in the second photo, I think you may be correct, possibly used on a slotting machine.

[DC31kParticipant @dc31k]

It is a cutter for a gear shaper.

Perhaps the best known manufacturer of the machines that use it is Fellows. In the UK, Drummond made one.

There are some YouTube videos by them on 'The Art of Gear Generation' and the Vintage Machinery site has a copy of their book of a similar name.

http://vintagemachinery.org/mfgIndex/detail.aspx?id=2186&tab=3

Dathan were or maybe still are a gear specialist.

Edited By DC31k on 24/04/2021 14:56:08

[Dave HalfordParticipant @davehalford22513]

There's normally a few on ebay

[JourneymanParticipant @journeyman]

Dathan are indeed still in business ** LINK ** http://www.dathan.co.uk/

John

[Bill Davies 2Participant @billdavies2]

I was in manufacturing and inpecting similar ones at W E Sykes, a gear cutting machine tool manufacturer, who also made gear shaper cutters, hobs, shaving tools, standard gears (for gear rolling tests; e.g. Parkson) and some gear measurement equipment. The front angle is probably 5 degrees, dish ground. If there is a second angle, it's only to reduce grinding wheel wear when re-sharpening. The clearance angle, relative to the axis, is probably 6 degrees. Note; all from memory.

The shaper cutters can take a lot of resharpening on the front face before they are beyond use.

Bill

[Michael GilliganParticipant @michaelgilligan61133]

Thank you, Gentlemen, for the very informative replies.

Quite pleased with my deductive logic … but embarrassed that I didn’t think to look-up Dathan

… I wrongly assumed that it was the owner’s name, not the manufacturer’s

MichaelG.

[Bill Davies 2Participant @billdavies2]

Looking again, I assume the double rake that Michael refers to is the chamfer on the back of the teeth, which makes them a bit safer to handle, and limits the regrinds. The profile changes towards the back and at some point could produce an inaccurate profile on the gear produced.

There were two methods used to produce the cutter's tooth space. One was to grind each flank separately to its involute shape. The wheel and work would 'roll' to produce the involute. The second method, using a reciprocating grinding wheel formed to the appropriate form using a Diaform pantograph to dress the grinding wheel. This had the advantage of allowing 'corrections' in the form such as chamfering the gear tooth tips, or to give a well-formed fillets for maximum strength. Slight undercuts produced by 'protuberances' on the cutter tip to give undercuts for gears that would be finished by shaving. This was the case for motor vehicle transmission gears.

Too much info, I know. I find gears and their cutters things of beauty probably due to my exposure to them in my youth.

There is no date etched on the top. It might be quite old, as 14 1/2 degree pressure angles were becoming less common, if not already obsolete, in the late 60s/early 70s when I worked for the firm.

It should polish up nicely, Michael.

Bill

[Michael GilliganParticipant @michaelgilligan61133]

Posted by DC31k on 24/04/2021 14:54:19:

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There are some YouTube videos by them on 'The Art of Gear Generation' and the Vintage Machinery site has a copy of their book of a similar name.

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The book is packed with information, and

the content of the videos is excellent … although the visual quality is dire !

[ the Acrylic models in particular ]

Shame the camera-man didn’t know about light tents

Many thanks

MichaelG.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Bill Davies 2 on 24/04/2021 21:03:50:

Looking again, I assume the double rake that Michael refers to is the chamfer on the back of the teeth, which makes them a bit safer to handle, and limits the regrinds.

[…]

Too much info, I know. I find gears and their cutters things of beauty probably due to my exposure to them in my youth.

There is no date etched on the top. It might be quite old, as 14 1/2 degree pressure angles were becoming less common, if not already obsolete, in the late 60s/early 70s when I worked for the firm.

It should polish up nicely, Michael.

Bill

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Thanks for the added details, Bill

As a matter of interest [but probably no importance], I bought it from the little ‘High Peak Vintages’ shop at ‘Hope Valley Garden Centre’ : **LINK**

Whats Here

… so it wasn’t far from its birthplace.

MichaelG.

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Edit: __ Just found this, which might be of interest 

https://www.researchgate.net/publication/269985733_IT_for_Product_design

Edited By Michael Gilligan on 24/04/2021 21:30:07

[Tim StevensParticipant @timstevens64731]

Right, Michael – what else do you need to start work on a Skeleton Clock … ?

Cheers, Tim

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Tim Stevens on 26/04/2021 10:51:36:

Right, Michael – what else do you need to start work on a Skeleton Clock … ?

Cheers, Tim

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Your question leaves me utterly bewildered, Tim

A pity, when all the other comments were helpful.

MichaelG.

[Howard LewisParticipant @howardlewis46836]

Interesting that it is etched, 18 DP, 14 1/2 P A , 54T, Depth .125

Ivan law's book "Gears and Gear Cutting" quotes the tooth depth for a 18 DP gear as 0.120

Possibly this is using an involute cutter, rather than a Fellowes shaper type cutter; or maybe not for an involute tooth form.

Would the dimensions be different for say, a cycloidal or hypocycloidal tooth form?

Howard

[DC31kParticipant @dc31k]

The cutter infeed, or tooth depth, is normally written as D + f, where 'f' is the clearance. Perhaps Dathan liked gears to be cut with a little extra clearance.

I suspect the calculation of 'D' will be the same whatever tooth geometry you choose.

Law gives 'f' as 10% of the tooth thickness at the pitch line, so Dathan's percentage might simply be bigger. Similarly, maybe the percentage for other geometry might differ.

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