lathe to cut 26tpi

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Well said

MichaelG.

The driving force behind imperial far eastern lathes is the US market where 26tpi is not common so little demand to have it on a lathe. European model engineers have been using 1.0mm pitch metric for years and all their fittings are sold in metric fine pitches so only the odd block around the world with an old British bike or old model engineer may want it.

Some of our machine tool suppliers don't even do imperial lathes and mills or are listing less in the way of imperial versions so you won't find 26tpi as standard on a metric machine.

Sounds like a good excuse for Neil to go out on a Jolley, I'm sure there would be interest in an article or three about visits to UK lathe makers to see these things being "made".

Edited By JasonB on 16/01/2019 14:56:48

I worked for a company who imported printing machines from USA as a kit and assembled them over here. There was a label attached which read Made in England when I once queried it I was told that the label was made in England

26tpi being rather close to M1.0 I reckon M1.0 would screw up to 10 or so turns into a 26tpi fitting before jamming. Might be 'good enough'?

A while ago I wrote a program to calculate gear combinations for the WM280 Imperial with the gear set [20, 25, 30, 40, 45, 50, 55, 60, 63, 70, 75, 80, 80]. Assuming I got the maths right (ahem), the closest the lathe can get is 26.25 or 2 x 13.09 tpi. I don't know if other gears have ever been available for the machine.

Interestingly, my Metric WM280 gets closer to 26tpi than the Imperial does. It has the set [ 20, 30, 45, 50, 60, 60, 65, 70, 75, 80, 85 ]. Apart from M1.0, the metric machine can also do 13.03 and 25.99

Found this in a blog about Bicycle threads on the Park Tool Website:

The bicycle industry has a long history of using many different thread standards. Both factional and metric sizes are in use. Some threads are also used almost exclusively in the bicycle industry. Below is a table of some of the threads and their uses. This table is not intended to be complete and exhaustive. Always measure diameter and pitch when possible to determine threading.

From the variety in the table it seems that bike repairers need a metric lathe than can also do 24tpi, 26tpi and 56tpi. It's another shambles!

Dave

PS Sorry about the formatting!

Edited By

Did not bother with a spread sheet for my Imperial 280 and got bang on 26tpi

40 spindle driving 65T

50T driving 80T

60T driving 75T on the gearbox input

Straight through position A

All supplied gears

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Admittedly not 'current' but some may be interested to know that the original Leica camera screw thread was 26tpi although it is often referred to as 39 x 1mm

MichaelG.

As said above, my 'British made' Boxford 330 lists 26 tpi as a thread it will cut with just one change wheel substitution.

And time to feel smug - my metric Boxford 330 will do every single thread listed above, including 24, 26 and 56 tpi.

As a coincidence, I rebuild old steel framed pushbikes!

If it's not too much trouble checking oily gears, what tooth counts have you got in your set please Jason?

I thought an Imperial 280 came with 20, 25, 30, 40, 45, 50, 55, 60, 63, 70, 75, and two 80s. You used a 65, which means either I made a mistake or the gears supplied with a 280 have changed. Could be another of my famous cock-ups - having a pair of 80s in the list is suspicious...

Ta,

Dave

Just come up from the workshop so will check tomorrow. I do have two 80T gears which are used for fine feed.

With my imperial 280 I got both a 65T gear and two 80T gears

as my new wm 280 imperial lathe arrived today I can confirm a 65t gear and 2 80t gears

My myford 254s has 26 tpi as standard in the gearbox.

I am only piling in on this thread because I have been gobsmacked to find that my 7 x 12 mini lathe as supplied to the US market comes with an imperial leadscrew and will cut both 20 and 26 tpi.

But I am sure everyone here new that so I will shut up about my new toy.

Why was I gobsmacked well it turns out that the leadscrew is imperial but the cross slide and compound are metric.

South Bend 9" lathes (like my 1949 model) can cut 26 TPI just FYI.

You are in good company - all metric series 7 Myford lathes had 8 tpi leadscrews.

Rod

3.2mm is close enough to 3mm for a myford? Not that even a 3mm pitch would be so useful!

The Leica Screw Mount used on Leica cameras for 40 odd years or so was 39mm x 26tpi - an interesting mix of standards.

Soviet copies were supposed to be all metric, 39mm x 1mm, but I am not certain about Japanese Canon screw mount cameras, however all three readily interchange (at least as far as the screw thread is concerned) and mount accurately and securely.

In that case my Chinese mini lathe which came with the crossslide and tailstock handles separate so I had to screw them into the knobs qualifies as British then?

3.175mm please.