Hello Paul,

I have just restored a Churchill Cub lathe from 1947 which is in the same sort of size range as your Student. The larger tooth count wheels that came with it are all made in Tufnol. They run quietly without any of the 'ringing' associated with steel wheels and they are stronger than those made in cast iron in that the teeth will absorb punishment rather than chip or break off. I had metal chips to dig out in several places without leaving significant damage that would interfere with their function..

For a lathe of that size I was surprised to find them to be fine pitched at 20 DP like Myford wheels, albeit a bit wider at 1/2 inch

I would recommend them from about 55 teeth upwards

Regards

Brian

Also look at the properties for Acetal & Delrin which are a tougher type of Nylon. Would have thought that Tufnol would be best though.

Steve.

If you do go the Tufnol route, be sure you understand the different fauna under which it is sold (e.g whale, carp, etc.). For gears, you will need the type that is made like plywood, not the type that is made like a Swiss roll. There has been discussion here on this issue relating to Myford tumbler gears.

I do not know if it allowed now, so read this before it is moderated: there is a UK-based eBay seller with the username of you_engraving who makes various change gears in delrin at very reasonable prices. With Colchester gears, it is often the centre spline that is more difficult to make than the tooth spaces.

Used aluminium to fix my Drummond-M small backgear cog years ago and the abuse it's taken is amazing

Hi Paul,

I made a set of change gears for my Boxford AUD lathe using Delrin. It works a treat and is easy to cut. I cut them from a 10mm thick sheet rather than having to get a selection of round stock. Luckily the tumbler gears were stamped 20 P.A. so I didn't have to guess the pressure angle. You can get a full set of gear cutters from the Chinese site which dares not speak it's name on this forum for $100 or so.

Regards,

Alan

Several of my change gears are nylon and they work fine , have cut 6tpi threads in cast iron using a nylon 85t gear no problem at all .

regards Geoff

Lots of people starting to use printed gears too, even for backgear on a SouthBend. Since the tumbler gears, first 3 of them, don't need to mesh with regular change gears I wonder what improvement might be had by using (printed) helicial gears.

Jeff Dayman –

Sorry but you are very wide of the mark by merely slagging off an entire range of materials and their manufacturer. I have no connection with the Tufnol company but have encountered its products at work and studied its web-site before adding a comment above; so I know that SRBF and SRBP are not "substandard" at all. Adding the company name makes your assertion merely libellous.

Like the other plastics you mention, they have their individual natures that render them suitable for particular purposes but not others, so are made in a variety to cover that. It is up to the user to select accordingly, and if the component fails in service you need establish if that was by choosing the wrong material or by using the right material to a poor design – i.e. the user's not maker's fault.

The Tufnol range is not "obsolete", but is still manufactured so is obviously still in demand; and their main customers are professional engineers of whom many could well be using such materials in costly projects to high specifications. Using them like the acetals etc. and various metals, as right for the specific components in the specific applications.

'

Or perhaps we should not use copper, tin and bronze either: older than exotic stainless-steels and titanium alloys by several thousand years, so obviously "obsolete".

If anyone wish to cut gears of Tufnol then it is plate and not bar what is a suitable material.

Gear made conveniently from bar won't last long.