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Myford motor pulley shake.

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speelwerk20/06/2020 14:54:16
375 forum posts
1 photos

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.

Michael Gilligan20/06/2020 16:30:27
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16422 forum posts
715 photos

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] crying 2 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.

Hopper21/06/2020 22:51:12
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4823 forum posts
105 photos

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

Paul Lousick22/06/2020 00:45:18
1554 forum posts
584 photos

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

DMB22/06/2020 07:25:51
1016 forum posts

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

DiogenesII22/06/2020 07:35:36
130 forum posts
50 photos

..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..

Lee Rogers22/06/2020 07:57:53
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82 forum posts
Posted by Paul Lousick on 22/06/2020 00:45:18:

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

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.

roy entwistle22/06/2020 13:52:44
1260 forum posts

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

speelwerk22/06/2020 14:52:52
375 forum posts
1 photos

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.

s2620002.jpg

s2620003.jpg

Hopper23/06/2020 00:07:07
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4823 forum posts
105 photos

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

speelwerk23/06/2020 16:49:26
375 forum posts
1 photos
Posted by Hopper on 23/06/2020 00:07:07:

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.

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