Smart & Brown thro tumble gear broken.

[mark novakParticipant @marknovak89985]

Hi everyone, New boy here and also new to lathes. I have been gifted a "Smart and Brown" A model Mk II lathe which had neglected and left in a damp shed for 20 years. I have spent a lot of time enjoying restoring it and now it all works, doesnt leak oil and is a superb machine apart from the "thro tumble gear nipple" on the handle which is broken. I have removed the grub screw on the handle but the handle wont come off. I dont want to force it, can anyone advise how to remove the handle so I can make a new nipple? Thanks in advance.

[mark novakParticipant @marknovak89985]

Broken nipple on thro tumble gear handle

[Thor 🇳🇴Participant @thor]

Hi Mark,

Welcome to the forum and congratulations with the S & B. I assume you have the manual, if not you might be able to buy one from here (https://www.smartandbrownlathes.com/our-lathes/) or here.

Thor

[Ady1Participant @ady1]

If its like a zero dial then the forward knurled bit unscrews from the rear knurled bit, or they turn independently because there may be a hole underneath for a grubscrew access

Or the knurled bit unscrews from the smooth bit

pipe grabs are handy, lol

Or it just unscrews…

[egaParticipant @ega]

Identifying the part will help. I'm not familiar with the "thro tumble gear" (or those lovely S&B lathes) but from the photo it looks more like the gear change handle.

[Bob StevensonParticipant @bobstevenson13909]

In view of this topic I took a look at my clubs S&B model 'A' mkll….the gear change lever is very similar and has a tiny hole in the knurled thimble which houses a small grub screw to take a very small allen key….. presumable when the grub screw is loosened the thimble may be removed thus disclosing the fixing for the lever….

[mark novakParticipant @marknovak89985]

Thanks for all your replies, I undid the grub screw and tapped the handle with a brass drift and it came apart (I think there might have been a burr on the handle) Now I just need to make the replacement part on my clarke lathe. Thanks again for the lovely welcome and all your help.

[old martParticipant @oldmart]

Hi, Mark, welcome. Ihave looked at the drawings and the selector for the Norton gearbox on the museums model A. There is no cmplete drawing, but the angle of the tip can be guessed reasonably easily. The grubscrew is 4BA and a 1/16 AF hex key is the right size. I include some pictures, the red part of the drawing is conjecture, as I did not dismantle the thing.

[egaParticipant @ega]

old mart:

I think your second photo's caption may explain where the OP's description came from.

[Ade PantonParticipant @adepanton25529]

I have a complete one but the casting is broken. All the the internals are good. If you want it PM me 😀

[old martParticipant @oldmart]

It looks fairly easy to make, mild steel would be fine. The diameter of the head end is 0.375". The total movement is about 1/4". The spring would be 3/8 od by the diameter of the hole in the knurled handle, it could be cut to a usable length. I have not tried to dismantle the museums one as the gearbox cover would probably have to be removed to re assemble it. If that is done, jointing compound is required in the right hand end as that is partly oil filled.

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