Getting started with gear cutting.

[Robin GrahamParticipant @robingraham42208]

My resolution for this year is to work patiently on something more complex than anything I've tried before. I would like to make a simple orrery and have set myself a target of 600 hours over the next year for the project – I have no idea if that's realistic, all I know is that jobs which are ten minutes in my head take at least two hours in reality … Time will tell!

First thing on this path is to learn to cut gears, so I'm looking for recommendations for books/tutorials etc which might help – I have Ivan Law's WP series book which is great in some respects, but doesn't really tell me what tooling/machinery I need within the limitations of my workshop.

Robin.

 

Edited By Robin Graham on 29/01/2019 23:30:58

[Robin GrahamParticipant @robingraham42208]

[EmgeeParticipant @emgee]

Hi Robin

A horizontal mill is good for gear cutting, it normally has low spindle speeds and geared table feeds, most have 1" arbors.
You will also need a dividing head preferably with a centre support, the head will have means to divide most of the gear teeth numbers required.

The gear cutters are available as sets or individual if only cutting a few gears within the range of the cutter, more details of the cutter numbers and gears they can cut are well explained in Ivan Law's book.

Gears can also be cut using a vertical mill if that's what you have or intend to purchase, you do need low speeds for gear cutting especially if cutting the larger tooth sizes in 1 hit.

Emgee

[Thor 🇳🇴Participant @thor]

Posted by Robin Graham on 29/01/2019 23:28:54:

First thing on this path is to learn to cut gears, so I'm looking for recommendations for books/tutorials etc which might help – I have Ivan Law's WP series book which is great in some respects, but doesn't really tell me what tooling/machinery I need within the limitations of my workshop.

Robin.

For machinery you will obviously need either a lathe with vertical slide or a milling machine, and a dividing head. For tooling you will need an arbor to hold your gear cutters and some gear cutters. You can buy gear cutters from RDG, or you can make your own. I have made my own gearcutters, I also made my own dividing head. To hold the gear blanks I made an arbor with one end fitting into the MT mandrel of the dividing head, the other end fitting the hole in the gear blank.

Thor

[BWParticipant @bw]

Hello Robin,

You can get gear cutters fairly cheaply on the internet

this is an interesting site http://www.helicron.net/workshop/gearcutting/

This page https://makezine.com/2010/06/28/make-your-own-gears/ shows you how to use Inkscape which is a freebie drawing package that has a gear generating module and you can generate lots of different gear profiles to see the difference between different pressure angles and DPs and Modules

single point cutter is an option but gear cutters seem to be so cheap you would only do single point cutter for the experience

I've cut a few gears with a single point cutter in a vertical mill, piece of HSS, grind it to the same shape as the gap between two teeth in a matching gear, using a primitive paper disk as a dividing head. See photos in my album called dividing. You can get by without a dividing head.

Use this web site to generate "primitive paper disk" https://www.cgtk.co.uk/metalwork/reference/divider

Neil has discussed making an Orrery and gear making in some of his threads and they would be worth finding.

Bill

[HopperParticipant @hopper]

I dont know of any other books than Ivan Law's that apply so well to the home workshop. It contains most of what is needed.

Re range of equipment needed, for the small brass gears in a typical orrery, you could probably use a lathe fitted with a vertical slide and small dividing head (or rotary table fitted with index plates etc). It seems that sets of metric module gear cutters are more widely available and cheaper than their imperial DP counterparts. For cutting a few brass gears the cheap sets from China might do a turn.

Depending on the size of lathe you have and the size of gears you want to cut, you might need a spacer under the vertical slide to lift the gear blank up above the cutter held on an arbor in the lathe chuck. Myford makes one of these. Not sure about others.

Otherwise, it could be an excuse to buy a small hobby mill such as the Sieg X2 etc. which others on here can tell you firsthand about.

[JasonBModerator @jasonb]

You may also want to look up Neils thread on making his jovilabe, did not use anything special just a home made cutter, pics are here, I'll let you search out the thread.

[Michael GilliganParticipant @michaelgilligan61133]

Robin,

Unless you intend making a very large Orrery … I recommend this book by J. Malcolm Wild:

**LINK**

MichaelG.

[Brian HParticipant @brianh50089]

Just a thought. Are the tooth forms in an orrery similar to those used in clock works or are they involute forms used in power transmission.?

Brian

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian H on 30/01/2019 07:42:24:

Just a thought. Are the tooth forms in an orrery similar to those used in clock works or are they involute forms used in power transmission.?

.

Traditionally they are cycloidal, but in practice, either should work.

MichaelG.

[Martin KyteParticipant @martinkyte99762]

You definitely want clock wheel style gearing. You can make flycutters for cutting the gaps. Don't be overbothered about tooth form. If you filed the teeth you could get it to work not that I'm suggesting you do. It's only running at very slow speed, there is next to no power transmitted, you don't have to worry about a bit of backlash or cyclical error. The drive is geared down and not up as in a clock so everything is much more forgiving.

Go for it.

regards Martin

[roy entwistleParticipant @royentwistle24699]

Robin

There are some wheel and pinion cutters in the for sale adds at present

Roy

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Martin Kyte on 30/01/2019 09:31:15:

You definitely want clock wheel style gearing. You can make flycutters for cutting the gaps. Don't be overbothered about tooth form. If you filed the teeth you could get it to work …

.

Martin,

Having suggested that Robin should not be over bothered about tooth form … I would be grateful if you could explain what you mean by 'clock wheel style gearing'.

… I am genuinely confused.

MichaelG.

[Martin KyteParticipant @martinkyte99762]

Fair question Michael, I have to think what I do mean now.

It was more of a general encouragement to think in terms of horological gearing and techniques rather than power train gearing. Malcolm Wild or John Wilding rather than Ivan Law if you need to refer to books. So brass wheels (Half hard leaded CZ120) cut from thin-ish sheet material. Use a commercial cutter of your chosen module or make a fly cutter which is just a piece of silver steel turned with a radius tool to generate the addendum curve with the dedendum as a straight portion. File or grind to half the diameter, put a clearence angle on the tip harden and temper and polish the flat face. Or for this job you could cut the teeth with a slitting saw and round the tops of the teeth with a file. It's going to be a very forgiving mechanism.

As far as not overbothered with tooth form I didn't mean somewhere between involute and cycloidal what ever that would be but to aim for a cycloidal form (straight sides, round top) but don't worry too much if the shape is not spot on to theoretically correct.

regards Martin

[Michael GilliganParticipant @michaelgilligan61133]

That's fine, Martin … Thanks

I'm happy that we are on the same wavelength.

MichaelG.

[BazyleParticipant @bazyle]

Since you are making smallish brass gears in the main you don't need a milling machine or a dividing head. You preferably want something running faster than a horizontal mill anyway.
Aim for an indexing system for your lathe mandrel; there are lots of techniques discussed before on this forum all a fraction of the price of a dividing head.
Then do the cutting with a clockmakers cutting frame and a flycutter or gear cutter if you find some. You don't even need a vertical slide since you can make the frame to mount in your normal toolpost at the right height from the start.

Cutter frame  Seventh picture down, but I do like the one higher up.

Edited By Bazyle on 30/01/2019 16:26:34

[Iain DownsParticipant @iaindowns78295]

Slightly (but not much) off topic, but has anyone used the cheap Chinese gear cutters found on eBay? There's a set of 8 advertised for about £37 which is roughly what you pay for one supplied in the UK. Other sets range up to £45 or so.

I don't expect them to be high precision and be able to cut steel for 20 years full time every day, but I would have hoped it would survive a few years of a hobbiest (who would probably only cut a few dozen years in that time).

Iain

[JasonBModerator @jasonb]

As you already have a vertical mill I'd be more inclined to use that, it will happily spin a typical clockmakers size cutter at 1500rpm or so. You then just need to come up with a way of dividing, a rotary table would be the more versatile in the long run and get more use in the future.

This guy goes into quite a bit of detail about making his on just small Sherline machines, you can do it without the electronic dividing though it does look more appealing than winding a handle round and round

 

Iain, My thought son the cheap gear cutters here

Edited By JasonB on 31/01/2019 09:21:48

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 31/01/2019 09:17:06:

This guy goes into quite a bit of detail about making his on just small Sherline machines, you can do it without the electronic dividing though it does look more appealing than winding a handle round and round

.

That looks a great site, Jason … and new to me

Thanks for the link.

MichaelG.

[JasonBModerator @jasonb]

Michael, the 3D pdf linked to below this video when viewed on you tube is quiet good to look around and see how it goes together, he explains how to use the pdf in the video. probably need to download and then open the pdf to get it to function.

 

It's nicely done and I like the more modern look to it, also got a lantern gear in there for good measure.

 

Edited By JasonB on 31/01/2019 09:40:52

[Robin GrahamParticipant @robingraham42208]

Thanks for replies. I do indeed have a small vertical mill (WM14) and also a Vertex HV6 rotary table, but no tailstock or dividing plates as yet. The HV6 is too big for the mill really, but has proved useful – I might be able to fit it all together for gearcutting.

By one of those bizarre twists of fate which happen from time to time the missus gave me a pile of books to sort out today (I have accumulated too many apparently) and Ivan Law's gearcutting treatise was second from top. I shall re-read with more diligence.

Robin

[JasonBModerator @jasonb]

Considering the diameter of some of the gears you have to cut you will need to pack up a smaller rotary table so may as well stick with the 6".

Debateable if you really need the tailstock, with a stout arbor and backing plate you could cut those without tailstock support.

[not done it yetParticipant @notdoneityet]

I bwould agree with that, Jason, but if one uses a long arbor, one can locate the rotary table close to the end of the table – well away from the head and any slight concentricity of the set up will be much less if mounting the workpiece closer to the supporting tailstock.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by JasonB on 01/02/2019 07:12:07:

Considering the diameter of some of the gears you have to cut you will need to pack up a smaller rotary table so may as well stick with the 6".

.

Which is, of course, a logical justification for the compact layout of the traditional horological 'wheel cutting engine'.

… it's certainly not impossible to do this job on a vertical mill, but it does seem to invite complexity.

MichaelG.

[JasonBModerator @jasonb]

I would have thought using what you have already got was less complex than making a cutting engine and indexing plates to suit.

[Author]

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