Clausing 5914 - Loose spindle bearing tightened

At Clausing's suggestion, I tightened the spindle bearing take-up nut, which adjusts the preload on the spindle bearings, by about 1/4 turn.

The headstock now warms up if the lathe is run constantly; previously, there was no perceptible temperature change. In retrospect, the failure to heat up after running for say 20 minutes should have been sufficient clue that the preload wasn't sufficient.

Tightening made a huge difference. I can now just about manage Clausing's original high-speed smooth turning test, although the lathe is still right on the verge of chatter with the chuck. It turns out that higher speeds chatter less, probably because one can get above a major resonance. The chips came off hot and blue. The depth of cut is

0.125" (0.25" diameter reduction) and the feed is 0.0026" per turn. I think I had to back off somewhat on the depth of cut, but it was in the range.

Then I went back to the 5C collets. Now I'm able to take a 0.250" depth of cut (0.5" diameter reduction) out of a 1" diameter 1018 bar at 1600 rpm, in power feed (0.0026" per turn). The chip spirals off steadily, turning dark blue as it goes, the oil emulsion coolant boils on the workpiece, and the cut surface is a mirror.

The tool is a BXA-16N with pos-neg carbide inserts.

I was also able to cut the 1" bar off at 600 rpm in direct drive, with the SGIH 19-2 blade upside down and the lathe in reverse, a heavy spray of oil emulsion coolant, and a power cross-feed of 0.0013" per turn. I generated a spiral chip at least 6' long. This chip remained steel gray, and was not hot.

I'll have to try the BXA-7 cutoff tool again. Maybe it works now.

It seems that just about everything that is capable of being loose was loose on this lathe, and one by one I've found and tightened and/or replaced the loose parts. I don't think that this lathe saw much cleaning and adjusting, or preventive maintenance, and things quietly degraded over the years. Probably, people just shrugged and said it's old so what do you expect, and never thought to ask anybody who knew anything about machine tools if it was necessary to tolerate these problems. Or they were too cheap.

In any event, this lathe is beginning to act like a real lathe, and I bet a lot of things that didn't quite work right before will now suddenly work a lot better. This looseness had to have been undermining everything to one degree or another.

Joe Gwinn

Reply to
Joseph Gwinn
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It should be. That was the factory test to detect a latent problem in the machine that wasn't obvious on lighter cuts. With the 5" overhang and no support, I know this is a cut I could do manage on my 15" Sheldon, a 3500 Lb. machine, but it certainly isn't good for the lathe. The fact that you now CAN do a really serious cut like this sure seems to indicate you've fixed it! It turns out

Oh, you bet they will! The depth of cut is

You generally want quite agressive infeeds on cutoff operations, but if the work material absolutely won't work-harden, then you can get away with slower feed.

Well, the most important thing on the lathe is the spindle, of course, so if it isn't right, then nothing can be machined well.

Jon

Reply to
Jon Elson

That makes sense. And, even if the lathe is somewhat diminished by wear and tear, this is quite useable.

And big enough to sting.

Now the Sheldon ought to be able to spit out incandescent chips.

I'm still creeping up on just how aggressive I can be without excess danger to man and machine.

Yes. By the way, the BXA-7 is now able to cut a steel bar off at high speed. I bet the spindle was the problem all along, more so than the loose gibs. Well, it was both. The loose gibs caused extreme self-feeding, while the loose spindle caused chatter as well.

This follows a weakest-link theory. Fix one thing, and the next problem pops up. Fix that, and something else pops up. Eventually, one runs out of problems. Eventually.

Joe Gwinn

Reply to
Joseph Gwinn

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