Tom Senior light vertical motor swap

[Simon Williams 3Participant @simonwilliams3]

If a light load on the quill helps, how about changing the quill bearings to be the -2RS style with double rubber seals, lubricated for life. These usually have a bit of passive resistance as a consequence of the seal.

Unless it uses angular contacts of course. Fairly sure mine is standard single row ball bearings, though it is some time since I had it apart.

Mine is the earlier version with a single keyway rather than a spline. It does rattle rather with a face mill but it hasn't failed yet.

[Andrew SkinnerParticipant @andrewskinner94774]

Posted by Simon Williams 3 on 02/01/2023 17:02:00:

If a light load on the quill helps, how about changing the quill bearings to be the -2RS style with double rubber seals, lubricated for life. These usually have a bit of passive resistance as a consequence of the seal.

Unless it uses angular contacts of course. Fairly sure mine is standard single row ball bearings, though it is some time since I had it apart.

Mine is the earlier version with a single keyway rather than a spline. It does rattle rather with a face mill but it hasn't failed yet.

That would be a good idea, that I might save till the bearings need changing.

I had some thoughts about the backlash in the X and Y directions. The screws are more worn in the middle, and I guess there’s some wear in the feed nuts as well. There’s a company in the US (Roton) that supplies Acme LH 5 tpi threaded rod for only about £12 per foot. With this, and a suitable LH thread tap, could I not make up some new feed screws/nuts?

[old martParticipant @oldmart]

The spindle bearings are both taper roller, so sealing is not likely in the inch size needed. I had trouble with overheating which had me running around in circles when preloading the new bearings. It turned out to be bottom seal to blame, even though it was the exact size for the spindle nose. It was a double lipped seal with a garter spring, and it took 2 stages to solve the overheating. The garter spring was first removed with margial success, then I completely removed the main seal leaving only the front lip. That did the trick, after all the seal was only there to prevent contamination getting into the bearings, the grease was not about to pour out like oil would.

There are several sources of ACME leadscrew material in the USA, but getting it sent to the UK might be difficult. If you can get some, get nuts at the same time. Kingston Engineering in the UK have that type of threading, try googling for them. If you had to get more than you wanted, there are several Tom Senior people on this forum who would be interested. Unfortunately although the X and Y axis leadscrews are both the same size, they are left and right handed.

For now, the heavy grease will definitely help with that backlash, I would try car brake grease.

Edited By old mart on 03/01/2023 16:30:57

[Andrew SkinnerParticipant @andrewskinner94774]

Currently building up a mill control box (rev-off-fwd, e-stop, power and fault lights, rpm meter, speed pot) from an adaptable box and bits.

Another question, possibly for Steviegtr – since the new motor shaft is only 40mm, and the mount adapter is 10mm thick, I’ve only got a small amount of shaft inside the pulley, which is leading to vibrations if the belt is set to normal tightness. I’ve left it loose for now.

The motor shaft has a 6mm thread in the end. Would it be feasible to turn a shaft extension of 19mm diameter, with a similar thread inside, and lock the two together with a length of 6mm studding?

Also, I need to mount the RPM sender somehow. How did you mount yours?

[old martParticipant @oldmart]

The rpm of a machine is the speed of the spindle, not the motor. With the Tom Senior, I bought a cheap optical rpm reader and put a reflector on the bottom of the spindle. The rpm was recorded with the VFD set at bottom, centre and top Hertz, (25-50-75) and at each pulley speed. Rod printed out a scale to fit behind the speed control pot, there is no particular need for exact rpm with a mill.

[Andrew SkinnerParticipant @andrewskinner94774]

^ thanks, the digital RPM meter and sender came with my Boxford VSL, but I managed to get its original Smiths meter going again, so it’s a free upgrade for the mill…

Edited By Andrew Skinner on 13/01/2023 18:21:23

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