Myford motor pulley shake.

If you check the Myford motor drive pulley then the larger diameter of it has a shake of around 0.015 mm on a close fitting turned arbor in the lathe. It also has a good fit on the motor arbor itself but if you tighten the grubscrew that secures it on its arbor, that shake increases to around 0.25 mm which of course gives unwanted vibration. Because there is very little room the grubscrew is placed off-centre.

Has anyone come-up with an idea to improve the securing of that motor pulley on its arbor? Niko.

Well-spotted, Niko

Mine [currently dismantled] is quite badly worn ‘bell-mouthed’ as a result of this.

Although the motor shaft has a keyway, the pulley was retained by just a single grubscrew [which must have come slightly loose] and the pulley, with its oversize bore was rocking on that.

Both motor-shaft and pulley now need attention

... but I will probably fit a 3-phase motor and then ‘bore & bush‘ to suit

MichaelG.

Running the belt looser reduces the vibration. Rebushing the pulley in steel would be a longer term solution.

Use a pulley that has a taper-lock bush if you want more accuracy with axial alignment.

Niko,

My S7 supplied new with an Ali pulley which eventually worked loose and Nottingham replaced it foc with a CI one. Apparently, they were CI then Myfords tried a change to Ali probably to cut costs. They went back to CI and appeared to know all about the problem so there must have been a lot of other complainants.

John

..with that kind of gap you may be able to insert slips of shimstock either opposite to (or maybe better), 120 degrees either side of the screw?

..a bit expedient, I know..

Cast iron wheels and taperlock bushes from Bearingboys. I don't think I'd use any other method having tried it once. Bearingboys a good UK company. Satisfied customer , no connection.

The motor shaft has a keyway, usually the pulley has a keyway, and yet manufacturers insist on just using a grub screw. Why not a key with a grub screw onto that ? In fact a properly fitted key should be sufficient.

Obviously cost must be a factor

Over the weekend I made an attempt to improve the pulley fitting by making a conical plug pushed in by a M6 screw in the motor shaft. It gave not the improvement I hoped for but a wobble of around 0.10 mm is good enough for me. Niko.

Very ingeious. Your own version of taper lock. Neat.

Thanks!

I should have made the taper a little less steep, 2 instead of 3deg. Niko.