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Endfloat Myford Super 7 and thrust bearing condition

Query re amount of pre loading adjustment to reduce spindle end float

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Peter Turvey11/01/2019 14:56:52
9 forum posts
1 photos

I am resetting the spindle thrust bearings on my 1966 Super 7 to remove endfloat, following instructions in the lathe manual. Readjustment has taken the preloading adjustment collar on the spindle end about1/4 turn beyond the scribed original setting mark on the spindle. Endfloat is about 1/4 thousandths of an inch or less now. Given the age of the lathe, is this amount of wear in the thrust bearings acceptable, or should they be replaced? Have a rather heavy driling job to do soon, 3/4 inch hole in a 2 inch long phosphor bronze bearing blank hence all this adjustment.

Lambton11/01/2019 17:10:36
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666 forum posts
2 photos

Peter,

If the rear bearings are in good condition and have been correctly pre-loaded together then it should be possible to adjust the position of this pair of bearings to produce zero end float. Make sure that you carry out the instruction 3 on page 26 of the manual as carefully as possible. It is worth giving the spindle a light tap with a hide mallet the "seat" the bearings which may be sticking on the mandrel (or outer housing) a bit then test for end float again. It is helpful to have the catch plate on the mandrel at this stage as it gives you something to grasp and tap against when checking the end float. Also it will protect the threads and register of the mandrel nose. It is wise to check for lack of end float after the lathe has been used for a short time and re adjust if necessary.. Just take your time. and all will be well.

Eric

Brian Wood12/01/2019 19:47:14
1828 forum posts
36 photos

If I might just add, I would also check the temperature of both the front bearing and the rear bearings as you proceed with this heavy loading.

Warm will be fine, hot definitely not

Regards

Brian

Mark Rand12/01/2019 22:45:23
657 forum posts

The wear is more likely to have been in the front cone bearing than the ball thrust bearing at the back.

Chris Trice13/01/2019 03:44:15
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1332 forum posts
9 photos

Don't forget to lubricate the bearings with oil (not grease). I've now done the taper roller conversion on mine but the principle remains the same. I tend to adjust mine to fairly close tolerances but the acid test is that if you exert a firm force on the spindle from the tailstock, if things tighten up (the bronze bearing) then the two roller bearings at the rear of the spindle want to be adjusted forward just a gnats to stop the tightening up happening. This assumes you've already set the preload correctly with the lockable collar. It's important to lubricate the front bronze bearing with oil daily and I do it not only with the wick system but actually touch a drop of oil to the front and rear edge of the bearing and let the rotation of the spindle carry it around itself.

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