Tom Senior light vertical motor swap

Hi all,

Mine (with S-type head) has an old B56 frame single phase motor slightly bodged on, and I’d like to swap for a three phase/inverter setup.

Would it be best to make up a flange to adapt to a modern motor mount, or try to find an imperial one that bolts straight on?

Pulley bore is 5/8”, existing mount PCD (not used by bodged motor) is four holes at 5.500”

Many thanks

I fitted a three phase 0.55kW flange mounted TEC motor to my 1976 light vertical and it fitted perfectly without any alteration.

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.

I have done this & the full video of how I did it is here.

Steve.

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?

Thanks for the tips, especially the video.

Frank/Andrew, have your motor mounts already been modified? I can’t find a modern motor with 5.5” PCD flange.

Steve, I couldn’t see it from the motor plate, but I take it yours is an 80 frame with B14’A’ type flange?

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

Andrew, the original flange mounting on my machine has a 110mm spigot, bolts on a 130mm PCD and motor flange OD of 160mm The motor I fitted is 0.55kW at 50Hz and 0.66kW at 60Hz with a frame size IEC71. I believe the flange mounting is described as B5 with frame size 71. (Note B5 flanges are different for other frame sizes.) Bearing Boys sell a TEC motor of this specification.

Ah, mine’s different then.

While we’re on it, the spindle on mine knocks annoyingly when on the cut. I’ve traced the noise to rotary play between the spindle and its drive pulley. If I ‘brake’ the part of the spindle that protrudes next to the motor at the top, the noise goes away. On my machine, this part is a splined shaft.

Bearing in mind I’m fairly new to mills, would it be worth stripping the head down, and how would I take the play out?

Mine has the little tick when running. If i put oil in the front oiler nipple ion the Quill it stops for a little while. Pretty much i guess what you are saying.

Steve.

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

Thanks for the pics. I think you might be referring to radial play in the spindle?

What I have is backlash between drive pulley and spindle. For example, as the fly cutter takes a cut, the backlash is taken up, and at the end of the sweep, the cutter overruns until the next cut, where the lash is taken up again with a knock.

I plan to strip down anyway, so will keep you posted.

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

If your spindle is the splined type rather than the keyed version, there is unlikely to be much rotary backlash as the forces are very light. You should check that the grub screw holding the pulley on the short shaft with the internal splines (next to the pic showing the needle roller bearings) is tight. I milled a second flat opposite the existing one so two grubscrews could be used. There are 20 splines with an internal angle of 90 degrees, so the wear would have to be terminal before rotary backlash was noticable.

Edited By old mart on 28/12/2022 20:58:38

Right, I’ve finally fitted a 1 hp TEC motor with B14 mount on ally adapter flange as per the advice above. Cheers for that.

With the head stripped down, it appears that the play is indeed between the splined parts. The only slight ray of hope is that it’s similar all the way along the length, even the bit right at the top, suggesting that if I replaced the female part, that would make a big difference. I think the mill’s been used primarily as a drilling machine, given the awful state of the vice, which would have evened out the wear in the male splines,

Is there someone out there who could make a new female drive part? I could probably turn the round aspects, leaving just the splines to cut, or even fit a splined repair insert.

Since there’s no play anywhere else, I’m inclined to stop the stripdown there and reassemble with some new grease.

Edited By Andrew Skinner on 01/01/2023 14:51:56

I’ve done an album:

Edited By Andrew Skinner on 01/01/2023 14:47:21

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.

I have just found the drawing which was kindly sent to me via another forum. The details, as I recall, were to make a replica shaft, and the dimensions, particular the diameter should be compared carefully with your shaft. A new female part could be made with a longer length of spline, assuming it would not then restrict the 2 1/2" quill movement.

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?

Only when I’m using the fly cutter. I haven’t tried it with the new 3ph motor, which should be smoother, and the VFD hasn’t arrived yet.

I’ve temporarily rigged up the VFD from my morticer just for a test run, but I don’t want to change settings on that as it’s not an easy interface.