21/4/18 - Lathe!

The last few days have been flat out just fixing the lathe. I have had all the carriage in bits...long story but had the rack and pinion out of alignment with the bed and putting some downward pressure on the carriage. I've been chasing some "phonographing" which has turned up in the last few months on some of the cuts and suspected possible swarf under the carriage as a culprit giving it some springiness reflected in the cut.

Lots of work done. The rack dowel pins were holding the rack out of parallel...they were almost all removed and set up with a spacer block off the bed. A gasket added to the top of the apron gearbox to stop the pinion bottoming on the rack. Also noticed the fair share of paint and grit in the rack and pinion.

Swarf cleaned out of the apron which was coning from the cross slide area. Gearbox drained, and flushed.

The power feed shafts and lead screw were cleaned. Half nuts were jam packed with swarf.

The lathe was reassembled and a test cut done. There was a defiite improvement but still a small ripple on the cut.

The lathe was tried on several speeds and on low rpm with a lot of motor rattle the cut was horrible. Then turned off and disengaged the drive and wound by hand. Much better. So I realised that I had tightened up the belts and the tension and the way the motor supports on the head was introducing a lot of vibrations and harmonics...which would be much more evidenced if the spindle besring pre-load still wasn't enough.

Decision was made to inspect the spindle bearings so the head was dismantled enough to do that. I found that the main bearing behind the chuck had 3 brinells in it, but not able to be felt by hand. The outboard bearing looked worse and the rollers had skidded or somehow gotten some grooves possibly by something hard in there.

Also it was noticed the input shaft rumbles slightly.

So I thought a cleanup and flush of the bearings and a blow out with air might do for the moment...see how bad it is when there's no grit in the besrings with some more pre-load.

So the heastock was reassembled again with the same bearings with the plan to change the whole lot in the headstock at a future stage when I can see my way clear. The metal in the headstock oil even coming off the gears is something to be aware of.

The cut has definitely improved. The bearing pre-load cannot be underestimated, as also the much quieter operation with less tension on the belts.  I'll add a rare earth magnet into the bottom of the sump to pick up any other traces of metal floating around.

Happy steaming!

Nigel