ER16 collet nut modification

[old martParticipant @oldmart]

I got an er16 plate for the model club Emco SL1000 lathe and it came with a nut which takes a 25mm spanner. I have investigated the possibilities of getting a UM style nut, but find that the threads are different. The one I bought has M22 X 1.5 and the UM use M19 x 1 threads. I recon there is enough meat in the standard nuts for changing them into UM type even though the thread is larger. The part where the UM spanner fits is not over the threads, but over the collet holding area which is identical. The diameter at the thread end will have to be left larger than a UM nut.

What do you think?

[JasonBModerator @jasonb]

Sounds like you are looking at mini or slimline nuts if they are M19. You can get the UM style nuts for standard ER 16 collet holder threads too

https://www.cutwel.co.uk/catalogsearch/result/?q=er16+collet+nut

[Peter Cook 6Participant @petercook6]

What is the issue with using a 25mm open spanner? Overall nut size is not that much different, and the UM style needs clearance between the face of the nut and the thing being held, while the 25mm open ended doesn’t.

I use ER16 collets to hold wheels and arbours when working  on clocks. With 25mm (A type ) nuts I can position the wheels tight against the face of the collet/nut. With typical UM I would have to leave spanner clearance, although a C spanner could solve the problem.

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