I fitted a motor/inverter package to my S type. (Newton Tesla,very happy,usual disclaimer) Had to open up the recess in the mounting plate a bit but it was easily done on the Myford faceplate,soft ally and no special accuracy required. Also needed to elongate the screwholes a bit,easier if you have access to another milling machine.

Doesn’t seem complicated at all (per Andrew and Frank). Might need to ream the old pulley and alter the power-transfer arrangement (if keyed) if a 16mm motor shaft is involved?

I modified the spindle to use R8 and chose a 6 pole 0.75 Kw TEC with a B14 end mount flange to use with a VFD and retain the 4 speed pulley system. The flange is different, so I bought an aluminium plate and copied the old mount with the B14 size hole and fixings. The motor spindle is bigger so the pulley was modified and twin grubscrews fit in the milled down motor shaft key. The reason for a 6 pole motor was to run up to the original motor speed, but also to retain more power at lower rpm. You still need the stepped pulleys to allow decent torque throughout the full range of speeds. For your MT2 spindle, a motor of 0.55Kw would be the best size. I checked the motor spindle sizes for the 0.55Kw and the 2 pole is 14mm and the 4 and 6 pole use 19mm.

Edited By old mart on 26/12/2022 15:38:57

There are two types of drive between the front pulley and the spindle, I recon yours is like these pictures. You need to remove the front pulley and unscrew the 2BA screws which hold the bottom pulley/motor mount to inspect the needle roller bearings. They may be available from "Bearing Boys" or another bearing specialist. Ours were ok and just got a wash and new lithium grease. Check that the pulley is a good fit when re assembling.

Edited By old mart on 27/12/2022 13:43:08

That is play in the splines.

There is not a lot you can do to eliminate it other than remanufacture the mating parts.

You can mitigate its effects by biasing the spline against the pulley. Have a search for 'Bridgeport spline play' or similar terms to see what solutions others have adopted.

The machine has spent most of its life rotating in one direction, so the wear will be asymmetric. Buy a whole load of left hand cutters and use the unworn part. If you can turn the splined part of the pulley upside down, that might give it a new lease of life.

You can make a keyed collar that goes over the spline and is joined to the pulley with a spring wrapped around it such that it pulls the parts together. See picture in post #9 here:

https://www.practicalmachinist.com/forum/threads/how-little-clearance-should-milling-machine-spindle-splines-have.339379/

The above solution should not affect use of the quill.

That thread mentions a Downham jig borer that has an anti-backlash system, so look there for inspiration. Also look at anti-backlash gears (HPC have them – two half-width gears biased open with springs).

Another option when you are taking intermittent cuts is to clamp the spindle and pulley together. This disables the quill, but you can put the cut on with the knee.

Below is what I made to address the same issue on a Beaver. The pin stays in the pulley; the 'drive dog' clamps round the plain portion of the drawbar.

Edit: also search for 'anti-backlash spline' as there are some patents that might inspire you.

Edited By DC31k on 28/12/2022 13:17:12

The female part would be hardest to make, unfortunately, I was going to make a splined shaft, but ended up using the original top attached to the R8 bottom. I will find the drawing and show it to you, maybe somebody on the forum might be able to cut the splines for you.

Andrew, does your mill 'hammer' all the time whatever the cutter and conditions, or is it noticeably worse during some particular operations?

Does it ease up if you tweak any of the parameters?

Splat of heavy grease down the splines?

A light brake on the shaft ? An easy trial to see if it's worth pursuing would be to use your fingers on a suitable section of exposed shaft. All the usual disclaimers.