Myford 7, three step spindle pulley slipping

[Paul KempParticipant @paulkemp46892]

Gents,

My long suffering vintage S7 today lost speed at the chuck while again being rather unfair to it by facing a cast iron eccentric strap that only just clears the bed. To get under the skin I had to take a 30 thou cut which stalled the chuck. Investigating the drive is there all the way from the motor to the spindle three step pulley (no belt slip). The spindle pulley is slipping on the spindle. It hasn't lost drive altogether (yet) but it won't carry a decent cut without the chuck slowing down.

I seem to remember a recent thread which mentions this as a common problem? Have done a quick search but nothing relevant cropped up. So can anyone who has experienced this and fixed it give me some clues what you found and what you did to fix it?

Thanks,

Paul.

[Paul KempParticipant @paulkemp46892]

[KWILParticipant @kwil]

Check that the bronze gear is still being driven by the 3 step pulley, it is only a press fit.

Still applies if you are driving the chuck via the backgear.

[AJWParticipant @ajw]

It was me!
I had this on my ML7 and would lose drive under a heavier than light load.
Stripped spindle out and removed pulley from bronze gear. It was still a good fit so I warned the pulley and off it came.
All cleaned up and degreased I assembled it with Granville bearing fit.
Good as new!

Alan

[Paul KempParticipant @paulkemp46892]

Kwil / Alan,

Many thanks. Knew I had seen it somewhere in the near past! Spindle out later this week then and under the press with the pulley if need be! Doubt it's that tight though as at close of play I turned the chuck by hand and the motor / belts didn't move. You both mention a bronze gear, I maybe wrong if it's covered with grime but it looks like a cast one on mine. Will report back when I get it stripped down. I have plenty of various grades of loctite so hopefully not too much of an issue.

Thanks again,

Paul.

[Paul KempParticipant @paulkemp46892]

Gents,

Need another clue here! I have stripped out the spindle this afternoon and removed the change wheel, thrust adjusting ring, bearing ring and its little peg, and all three races of the bearing, no problem. However I now can't get the pulley / gear assembly off the spindle. There seems to be a thick spacer ring that sits inside the counterbore of the pulley which isn't showing a lot of interest in coming off? I gave it a very gentle push under the press with the pulley supported on blocks and it might have moved 1/16" inch. If it's tight all the way I don't want it scraping over the bearing surface of the spindle! How did you get yours off? (Yes you are right, the gear is bronze, just covered in black oil!).

Thanks,

Paul.

[AJWParticipant @ajw]

I know I have just fixed mine but I can’t remember the part you are referring to?
I heated the pulley and it came off quite nicely.

Alan

[Ian S CParticipant @iansc]

Beware, if it is held to a shaft with a grub screw, take out the screw, and put the key back down the hole, chances are you will find another screw under the first, sometimes this wears against the dimple in the shaft, but the real danger is if you try to remove a pulley held this way without removing the second screw.

Ian S C

[AJWParticipant @ajw]

I have just noticed you have a S7, mine is only a ML7 – perhaps they are slightly different in that area?

Alan

[HopperParticipant @hopper]

I'm confused. If it's an S7, with no removable bearing caps, how did you get the spindle and pulleys out of the headstock and into the press?

+1 on use heat rather than force to get the pulley off the spindle. Unless it has rusted on, it should come off fairly easily.

Can you identify on this Myford parts drawing, which part number is causing you trouble: **LINK**

Can you post pics of what you have there?

 

 

Edited By Hopper on 18/09/2018 05:14:57

[Brian OldfordParticipant @brianoldford70365]

Were it a S7 it would have a four step pulley. ML7 has 3 step.

[Michael GilliganParticipant @michaelgilligan61133]

Posted by Brian Oldford on 18/09/2018 08:56:32:

Were it a S7 it would have a four step pulley. ML7 has 3 step.

.

So may we assume that there is simply a typo in Paul's opening post ?

MichaelG.

[HopperParticipant @hopper]

Pics would sure help determine what we are dealing with here.

If it is an ML7, and not a Super 7, the pulley should come off by banging the left-hand (small) end of spindle down on a block of wood on the bench repeatedly. If more force is needed, it is better to use heat. A pre-operative soaking in penetrating oil or ATF etc may be in order too.

Edited By Hopper on 18/09/2018 12:13:17

Edited By Hopper on 18/09/2018 12:14:09

[Paul KempParticipant @paulkemp46892]

Thanks gents, sorry it's a plain 7 as indicated in title, as Michael suggested the S in the text was a balls up! It has bearing caps so spindle just lifted out of the headstock complete. I found a couple of YouTube videos of spindle work which show for reassembly the offending collar to be a tight fit and refitted by knocking on with a hollow tubular soft block. Although the linked drawing is not my machine the closest match is item 31, distance sleeve. I had already tried 'jumping' the spindle on a wooden bench. It's definitely not rusted, everything is liberally coated in oil as it has been for the last 40 years in our ownership. Not had chance to get back to it yet but a bit reluctant to use heat as its directly on the spindle so heat will conduct into it and they are both steel so there won't be a differential of expansion rates, it's also sat inside the recess of the pulley. Might have another go this afternoon.

Paul.

[Paul KempParticipant @paulkemp46892]

Update;

All fixed yesterday! The offending tight item was a distance collar that sits on its own register a little bigger than the bearing journal and buts up to a shoulder on the spindle where the diameter increases for the pulley to run. Ended up releasing the bull wheel, confirming it was loose on the spindle and then pressing the spindle through the lot. It didn't take a lot of force. The pulley was still a more than hand tight fit on the bronze gear so I heated the pulley giving an easy release by hand of the bronze bit. Cleaned up both mating faces with crocus and degreased. Heated the pulley to 75 deg C and reassembled by hand with loctite 64 something or other (can't remember the number off hand but it's a high strength bearing retainer). Tried heating the distance collar to the same temp but that refused to drop on by hand so put it back with the press. Again only light force required. Spindle refitted and thrust adjusted, original bearing shims retained as nothing has changed. Ran it light for half hour with a good oil feed, no heating of bearings. Tried the cut I was taking when the problem became evident, all good.

So now back to the job in hand, thanks for the pointers.

Paul.

[Howard LewisParticipant @howardlewis46836]

Thanks for the update!

This may very well be good information for others who are faced with a similar problem.

So many problem reports seem to have no posting telling the conclusion, (What WAS the cause, and the solution)

Howard

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