Preloading the angular contact bearings as per instructions, the preloading is determined by how tight you move the left hand end of mandrel adjuster. Clearance on the front taper bearing is determined by moving the pair of clamping rings form the point where rotation is just not possible to the specified position which gives the required running clearance. So it is prelaoding first, followed by the front bearing clearance, all by following the Myford written text.

Did you remember the spacer between the two bearings?

Are the bearings the correct way around?

Did you remember to give the left hand collar a sharp tap with a small hammer?

I had exactly the same experience with my Super 7, when it was nearly new. I was trying to use a rather brutish 'carbide'-tipped tool – a negative-rake metal-shifter. The only way chatter could be (mostly) eliminated was to tighten up the front bearing clearance. The bearing continued to run cool at high speed, so I thought the spindle may have been not optimally adjusted previously. Then I needed to drill from the tailstock, and the lathe stalled at the slightest provocation. Unfortunately, this behaviour is a 'feature' of this lathe – others have experienced the same.

The problem may be because of a lack of stiffness in the thrust bearings themselves – perhaps the taper roller mod helps. However, IIRC, with a sensitive indicator, I satisfied myself that the part of the headstock casting which carried the thrust bearings wasn't very stiff, when the spindle was loaded axially – a few 'tenths' movement could be induced wrt the bed. I don't recall being able to detect movement between spindle and the rear of the headstock. Incidentally, my Emco Maximat Super 11 coped with the tooling perfectly.

As you've discovered (and it sounds like you fully understand what you're doing), setting the position of the spindle is either a compromise, or you adjust it for the job in hand. It's a very sensitive adjustment. I guess most users settle for a compromise setting, which is where the lathe doesn't slow down with the heaviest anticipated axial load applied. But then look at the axial movement of the nose of the spindle, when loaded radially, and don't be surprised to see a couple of 'tenths' of movement. Remember, it's a light lathe, designed more for versatility than heavy loads. Despite its worship from its die-hard fan base, it's a dated design with many flaws: better* lathes are out there…

* Of course, it rather depends on what you mean by 'better'.

Andy,
It is a pity your profile does not give a clue as to your location. If we knew, one of the forum members might have been able to assist locally.

K

Andy – it may just be loose terminology, but now I'm worried that you seem to be still fiddling about with changing the preloading of the angular contact bearings (set by the split, threaded collar, at the end of the spindle). Essentially, once all the 'slack' is taken up, increasing the preload will achieve little, if anything, in terms of axial rigidity, but will cause the bearings to have a harder time – or fail. Do not over-tighten them. The relationship of the spindle to its tapered nose bearing is what needs careful fiddling. This is set by the two rings, using C-spanners, patience and suitable language. It's easy, but tedious. I think you know that…

The above instructions are correct, in principle (although be careful with the 12oz hammer…). Very small spanner angle adjustments are needed to get the best adjustment. In fact, you may find that you can change from a tightening spindle to a well-behaved one simply by bumping the spanner on the rear ring to make it a little tighter. I've always used the heel of my carefully-calibrated hand, not a hammer.

I suspect – but have no evidence – that the type of oil used in the front bearing may have a significant effect. Myford's recommendation may be rather old-fashioned. One day, I'll try something 'slipperier'. Any suggestions, anyone?

Have you replaced the spindle during your rebuild? I have had this problem which ws caused by the spacer (Item31 on the exploded diagram link below) not seating right up to the shoulder on the spindle but jamming just short. This is firm enough to seem like all is well when you adjust the front bearing clearence but when a thrust load is applied from the tailstock the spacer moves and the front clearence is lost. The quick way to solve this is as Chris says above adust the collars to give a generous front bearing clearance. Then tighten the split collar as tight as you can get it to ensure the spacer is tight to the shoulder. Loosen off and set the preload as normal. Then you can set the front bearing clearance.

If you want to fully diagnose the issue. Take the spindle out and inpect the fit of the collar (item 31) on the spindle. There are some new spindles around where the collar gets tight just before it contacts the shoulder. I did stone my spindle off just to ease the fit so it's only a matter of a few tenths but enough to cause an issue.

**LINK**

regards Martin