Thornton Miniature Gear Cutters

[MWParticipant @mw27036]

What's happened to them? I'm pretty sure their website is down.

Also, i've tried searching the forum for information about them but to no avail.

They sell quite expensive gear cutters but as far as i know they are one of the few who still make 7MM bore small gear cutters.

As an aside, has anyone read the "workshop practice series: gears and gear cutting" by Ivan Law? i've heard that in the book there is detail on how to make your own silver steel involute gear cutters, given how expensive the thornton ones seem (£99 a piece)

Michael W

[MWParticipant @mw27036]

[Russell EberhardtParticipant @russelleberhardt48058]

Thortons horological cutters are available from Meadows and Passemore.

Russell.

[Anonymous]

The Thornton website seems fine to me, and the prices seem slightly less than £99?

The Ivan Law book does indeed describe how to make an 'involute' gear cutter. The involute is actually modelled as an arc, so they're not exact, but in practice are absolutely fine. Of course the Thornton gear cutters are for a cycloidal tooth form not involute.

Andrew

[speelwerkParticipant @speelwerk]

I see no problem with there website, agree not many suppliers are left, I know **LINK** but they certainly will not be cheaper, you also have Bergeon Tecnoli cutters but do not find them very accurate. Niko.

[John HaineParticipant @johnhaine32865]

Michael, there are several sources of information on making your own involute cutters by the "two button" method. One of the best IMHO, because it explains how they are designed as well, is on Mike Cox's site:

**LINK**

I've made similar cutters using CNC on my lathe, which is more straightforward once you have the lathe! (Mind you it ought to be possible to make a simple attachment to move the tool in the required circle.)

**LINK**

IIRC Ivan Law's book also tells you how to make cutters for "cycloidal" gears in a similar way – if not him, them there are some articles by Don Unwin that have details, I think in ME, and also in Wilding's "Wheel and Pinion cutting in Horology" book.

[MWParticipant @mw27036]

I must be going senile or something, the address i'm using comes up with some free webs thing but i'll sort it out.

I may try to see if i can loan Ivan's book from my local library though i'm sure many would argue it should be a permanent addition to the literature.

I noted your article on making taps, Andrew and quite enjoyed the thoroughness of your build, the taps look near professional and alot better than the attempts i've made in the past, it was well worth the article because alot of people are simply unaware that you can do this.I do wonder on why you chose to make "serial taps" as in, decreasing diameter through the set, rather than the old fashioned stages of tapering, not that i take issue with it, just merely wondering.

Michael W

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Michael Walters on 25/04/2016 15:38:31:

I must be going senile or something, the address i'm using comes up with some free webs thing but i'll sort it out.

.

Michael,

This link to the website seems fine: **LINK**

… I have linked to the Terms & Conditions page. [listed prices exclude VAT, and all that good stuff]

MichaelG.

[Anonymous]

Posted by John Haine on 25/04/2016 15:14:35

IIRC Ivan Law's book also tells you how to make cutters for "cycloidal" gears in a similar way……

I must have an early version of the Ivan Law book? I've looked through the whole chapter on making gear cutters and it doesn't seem to mention cycloidal cutters, although the various types of cycloidal tooth forms are discussed earlier in the book.

Andrew

[KWILParticipant @kwil]

MichealW

If you are making a square form leadscrew, then serial taps cut deeper in stages, reduces the effort required.

[JasonBModerator @jasonb]

As KWIL says there is a lot of metal to remove in one go so doing it in steps is easier, much like using a broach where you add shims to get to full depth. Also if you look at commercially available ACME taps they either have a very long taper or look like two taps in one as the two sections are sequential.

[John HaineParticipant @johnhaine32865]

Andrew, obviously I don't recall correctly! I must be confusing the book with Don's article.

[Anonymous]

Michael: I'm glad you liked the article. KWIL and JasonB have discussed the basic reasoning for using serial taps. They are pretty standard for square and Acme threads, and the number and diameters of the taps in a series are detailed in Machinery's Handbook. It is worth remembering that square and Acme threads are normally tapped pretty much full depth, unlike normal V threads where a percentage of thread depth is fine. The teeth on the taps are quite wide at the OD and so are taking a significant cut, which can overload the teeth if the cut is too deep. I broke one of the teeth on my taps when tapping the bronze nuts.

Serial taps can also be used for standard V threads, particularly in tough materials. The only source of V thread serial taps that I am aware of is ArcEuroTrade.

Andrew

[RobCParticipant @robc77385]

The P.P. Thornton website was 'updated' over the weekend, so has been a little intermittent for some. I spoke to them yesterday and they are very pleased with the new site, but a little disappointed that it was not as instant an update as they imagined.

The revised site is much more 'consumer friendly' and allows you to see examples of their cutters, along with prices for the different variants.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by RobC on 26/04/2016 09:19:44:

The P.P. Thornton website was 'updated' over the weekend

.

Rob,

Thanks for the info.

… I thought it must be a recent update when I saw the 'Hello World' entry !

Unortunately your hyperlink is wrong

… If it's not too late, you could edit the post.

… otherwise, the link I posted yesterday is O.K.

MichaelG.

Edited By Michael Gilligan on 26/04/2016 09:50:15

[IanTParticipant @iant]

Yes, it worked just fine for me Michael,

I was curious, as I've got a couple of their cycloidal cutters somewhere – although I cannot for the life of me remember where they came from now. I don't think I'll ever make a clock myself though – I have a long enough 'Tuit' list already and it doesn't seem to get any shorter I'm afraid.

Regards,

IanT

[Russell EberhardtParticipant @russelleberhardt48058]

Posted by Andrew Johnston on 25/04/2016 22:56:49:The only source of V thread serial taps that I am aware of is ArcEuroTrade.

I can't find anything other than serial taps here in France.

Russell.

[AjohnwParticipant @ajohnw51620]

Posted by Michael Walters on 25/04/2016 14:33:44:

What's happened to them? I'm pretty sure their website is down.

Also, i've tried searching the forum for information about them but to no avail.

They sell quite expensive gear cutters but as far as i know they are one of the few who still make 7MM bore small gear cutters.

As an aside, has anyone read the "workshop practice series: gears and gear cutting" by Ivan Law? i've heard that in the book there is detail on how to make your own silver steel involute gear cutters, given how expensive the thornton ones seem (£99 a piece)

Michael W

Yes it's in number 17 of the workshop practice series. It's also about on the web usually missing mounting the buttons on a 5 degree slope to gain front clearance. A bit of back rake can be ground on the top as well. Or if the buttons are mounted flat around 5 degrees of back rake but make sure the cutting edge is very slightly below centre as there is no front clearance. These are then used to make the cutter. Simplest is a circular blank that then's gashed to make one cutting edge or by offsetting a blank in a jig several cutting edges.

When it comes to cycloids as used in clocks there are a number of standards. Like most things they are approximations so that cutters can be made. There is also one aimed at use with lantern pinions. These are I strongly suspect the main gain with cycloids as pinions with differing tooth counts need specific cutters.

Some links

**LINK**

and making the cutters

**LINK**

A search for David Creed Making Clock Wheel and Pinion Cutters will also find that.

John

–

[David lawrence 3Participant @davidlawrence3]

The Thorntons web site is up and running and I am more than surprised that they want £ 10.00 bank charge to accept payment, they don't take credit cards but do take pay pal. When I run a mail order business upto last year my bank charge for direct bank transfer was around 40p. rather excessive I think but the cutters are great.

[MWParticipant @mw27036]

It is indeed back up and running, thanks for the links john, the first is worth its weight in gold, simply amazing what he can achieve on his small machine, makes me want to apprieciate my sherline a little more than throwing it in the back of the garage, i do like my bigger lathe but theres nothing worse than turning small parts on a big machine. Nothing technically wrong with it, it just wears on you after a while of fiddling around. 

Michael W

 

Edited By Michael Walters on 26/04/2016 18:32:47

[RobCParticipant @robc77385]

Posted by RobC on 26/04/2016 09:19:44:

The P.P. Thornton website

Oops, looks like this forum uses a slightly different method of linking than the others I am used to.

**LINK**

[AjohnwParticipant @ajohnw51620]

It might be worth adding a sacrilegious view of cycloid gears. This shows the a pinion in mesh with a wheel and the pitch circle diameters.

The pinion flanks are radial – part of the "aim" of cycloid teeth. If the gears mesh like that on purely radial points there is no pressure angle which is reckoned to cause wear on the shaft that carries them. These have the full profile though. If the other parts come into action bang goes no pressure angle and also no sliding contact.

The wheel flanks are partially radial because having exact radial teeth on all tooth counts would mean that a different cutter would be needed for each of them. So that is only usually done on low tooth count pinions. Rather than having the curve down to Beelzebub on the end the wheel teeth ends are just radiused. This gets them out of the way neatly and can be done on pinions too, in some ways these would give the pinions a better action. They can work out with lantern pinions too.

Like all practical gears they need some clearance. Not reckoned to matter on clocks etc as they only rotate in one direction but departures from true curves will interfere with all aspects.

Then they are depthed to run nicely, what ever that means and then supported in holes which in engineering terms might be called rather big for the shaft that is in them. Friction?. Codge wallop Any clearance will result in point contact unless carefully sized to take account of specific lubricants and load and speed ranges. So bang goes the careful depthing unless it isn't that critical but that would upset the other aspects of this type of gear anyway.

Couple of links

**LINK**

All true but for best action involutes do need correct depthing. Cycloids are often claimed to not suffer from this problem but that's clearly a load of bull. I have seen claims that a 14 1/2 degree pressure angle came from figures initially found on practical cycloid gearing presumably made by engineers. 20 degrees has since been found to make very little difference. When what this means in practice is looked at that is hardly surprising.

Also when rounded end pinion teeth can be used and other aspects.

**LINK**

Round over cutters are sometimes seen on ebay but making a cutter to do that wouldn't be difficult and the rest can be taken out with slitting saws. Thin one for the flanks and a fatter one to clear out the middle.

John

–

[Nick_GParticipant @nick_g]

Posted by Michael Walters on 25/04/2016 14:33:44:

They sell quite expensive gear cutters but as far as i know they are one of the few who still make 7MM bore small gear cutters.

Michael W

.

Michael,

Just being nosey and curious as to what you are making with these. – Any chance of a write up thread as I need to cut some gears soon and have never done it.

Cheers, Nick

[Author]

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