Why Can't I get my DTI to Repeat

I don't know how you are checking preload but I wanted to tell you how Emco does it. With the lathe cold, in neutral and a chuck mounted on the spindle, they spin the chuck by hand as hard as they can. Preload is adjusted so that the chuck stops after 1 to 1-1/2 revolutions. Emco uses P6 precision tapered roller spindle bearings and this procedure, as simple as it is, works well. My chuck stops after 1 full revolution, spindle has zero run out, doesn't get hot and it has remained precise since I've owned it (about 6 years at this point). You might see how this compares to what you're doing.
 
Interesting,
Mine will spin several revolutions in neutral with a chuck in place. I feel I could go a little more. So far the more preload I give it the better the runout gets.
 
When Emco built their lathes they used a 3 jaw chuck but I don't think that makes much of a difference.

This preload method was detailed by an Emco engineer who worked in the factory. The Super 11 was built to a DIN tool room standard so it had to pass inspection at almost every stage. The worker who built the actual lathe used this adjustment method on the floor as the lathe was built, then it had to pass inspection.

I would consider tightening up on the preload until the chuck turns 1 to 1-1/2 revolutions, then run it at medium speed and watch for heat build up. It should warm up but should never be so hot that you can't sit your hand near the bearing. Then check the run out and see what you see. If you use this method, keep an eye on things to make sure the bearings don't run hot over time. My lathe gets only slightly warm when I put my hand near the front spindle bearing.
 
ddickey said:
Gotta be four or five times.
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Duane, that short video does not appear to show enough preload. Mikey's advice is probably closer to ideal. Be careful not to damage the spindle bearings when testing the results after tightening the preload...
 
Thanks Bob. I'll be careful. Not going to get to it tonight.
Mike, that ER chuck on there is heavier than my 3J.
Pulling my head apart tonight on the mill.
 
Top of the mill. lol
Putting that new quill in.
 
ddickey said:
I've never pulled the HS apart. Pulling gears off/out might be a task I haven't the proper equipment for.
Pic of my HS from a previous post.
View attachment 293269
Click to expand...

Yeah thats kinda what mine looks like inside, although once the omg factor was passed it was more of a fiddle / annoying than actually difficult. :)

Milage may vary consult ur owners manual etc. (or if any one hear has the same lathe thats always very helpful :) )

Stu
 
I'm mighty happy to hear that you've identified the issue! It was a real puzzler. But you're on track now.
 
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