Lathe gears

James,

Just dug my old school test book on Engineering Drawing and in it has a chapter on involute gears. It give the basic theory on gears and formulae for calculating the various bits of a gear wheel.

If you want me to, I can scan the chapter and e-mail it to you (PM me your e-mail address).

Regards

Luigi

Hi Hansrudolf,

thanks for pointing that out, I actually meant 'how big the gear teeth are', but of course this is also related to the size of the gear diameter. For example a 60t gear of 0.833mod. would be 50 mm diameter, while a 60t gear of 1.5dp would be 90 mm diameter, hence the size of the gear wheel is relative to the module for a given number of teeth.

I apologise for my omission and oversight and hope that I have not irritated you so much as to spoil your Christmas celebrations.

Best regards and seasons greetings,

Terry

If, as is quite common on smallish Chinese lathes, the change gears are Mod 1, then it might (depending on the bore of the gears, or rather the bore of the keyed bushes which fit in them and run on the spindles on the gear quadrant) to use the readily available and cheap acetal gears from a minilathe. I think those gears are 12mm bore, and the bushes are 8mm bore.

James, examine the gear you have. If its outside diameter (across tooth tips) gear in millimetres is equal to (or just a bit less than) N + 2, where N is the the number of teeth, then it is a Module 1 gear. Of course, if the spindles are missing from the quadrant so you have to make your own, you could make them 8mm diameter.

The gears for the drive to the milling head drive may be to a different, probably larger, module, but places like HPC or even Technobots may be able to help.

Andy

Arceurotrade do spare plastic gears for the C3 minilathe for £2-£4 each, they also do a metal set for a bit more, don't know if they will fit your machine but they are very much cheaper, all mod 1.

Billy.

I've got a feeling that the change gears on the CL500 are a bit bigger than that, sort of Myford\Boxford size, but it's a long time ago so I can't be sure.

This is amazing thank you so much to everybody that has replied. I've learnt so much. I'm going to sit down and figure them out now haha.

James,

Don't get sidetracked that much that you forget we need to number of teeth and the OD of the existing gear.

Will check the warco version machine tonight.

I've seen CL500 change gears - they are larger teeth than mini-lathes and made of metal.

Neil

The warco is called WMT300 now do not know if the 300 is smaller than a Clarke 500 or just badge engineering ?

However measured one up tonight and the 70 tooth is 72mm OD so definitly 1 MOD.

The gears on this one have 4 splines on a 15mm shaft.

And the milling head I'm guessing at 1.5 MOD 45 teeth mitre gear, this machine doesn't have a milling head, been removed, so can't measure the mating gear and this one is hard to measure without a strip down.

So we need some information from James before anything else can be worked out.

Are they 1 MOD ? Need to numberof teeth and the OD of the only existing gear

And what is the fitting ? Even if the spindles are missing the end of the leadscrew will give this information as the same gears have to fit this.

As has been remarked earlier ARC sells a metal gear set for the C3 at about £58 and by the time you take buying gear cutters, messing about, blanks etc to me it's a no brainer to use chequebook engineering.

No, Terry, not much Christmas celebrations here and no need to apologise! It was not you who wrote that description I think, or are you khkgears.co.uk perchance?

Kind regards and greetings too,

Hansrudolf

Right just got the original of the machine and I've actually found a second one as well whoo . The largest one I've got is 56 tooth and measures 58mm OD, the other is 36 teeth and measures 38mm OD. John my gears have the four splines in the middle the same as yours and mount in the back of the machine the same way as shown in your pics.

all the best James.

Terry,

That was a very nice exposition on gears forms. Just to clarify the quote above from your post to Hansrudolf:

I think a typo has slipped into your calculation. Diametrical Pitch (DP) =N/ Pitch Diameter (PD). Therefore DP=60/1.5 = 40. However, it has become convention for metric gears to be defined by the Module (M) system measured in mm and for imperial gears to be defined by the Diametrical Pitch (DP) system in inches. Thus a conventional 60t 1.5DP gear would have a pitch diameter of 60/1.5 =40 inches. As mentioned above, the overall diameter would be (60+2)/ 1.5 = 41.3 inches. I mention this latter point to avoid confusing those who are familiar with the sizes of their 20DP Myford changewheels - a 60 tooth 20DP myford changewheel is 62/20=3.1 inches diameter.

Best wishes,

Rod

James,

OK so you are looking at 1 MOD gears same as the Sieg C3 lathe as sold by ARC but they don't have 4 splines, just 1 keyway.

Might still be cheaper to buy a set from ARC and modify the centres.

By coincidence, I've just been messing with the 40T mini-lathe gear I use as an idler to reverse my leadscrew. It looks like this pic . The central "boss" is 18mm diameter, so there's not much meat to cut into, and it would be hard to match the curve round the bottoms of the four "keyways" shown in John S's last pic.

It might be easier to make 8mm gear spindles, to match the simple keyed bushes which suit minilathe gears, though that wouldn't help at all when it comes to fitting any of the various gears on the end of the leadscrew.

Andy.

Edited By Andyf on 19/12/2012 00:09:22