While cleaning the bottom half of the headstock and repairing the spindle brake, I discovered the chuck end of the the backgear/countershaft was extremely worn.  The gap you can see on the top of the shaft is nearly 1/8" across.

You can see the bearing surrounding the shaft, mounted in the steel bearing assy.  The assembly is pressed into the headstock casting from the outside and locked in place with a cross setscrew in the foreground hole.  The oiler feeds down through a hole in the bearing assy, around both sides of the bearing, emerging onto the journal surface through a wick on the bottom.

The 1 3/8" diameter shaft was so loose it could be moved around by hand.  It is also heavily scored, as seen below, in some places the diameter decreases by about .010.

I built a press to extract the bearing assembly.  The foreground legs are just wide enough to straddle the bearing assembly.  The background legs are closer together, straddling the shaft.  With the front legs outside and the back legs inside pressing on the bearing assembly via wood shims, out it came neat as you please.

This is a view of the top portion of the assembly.  You can see the gummed up dirt in the top oil channel.  The wicking in the bearing bottom was even worse.

But it cleaned up OK. 

Thankfully, the bearing and journal on the other end of the countershaft are fine.  But the problem is I can't get the shaft out!  With the shaft pulled from the other bearing as far as it will go, theres still about 1/4" inside and no slack amongst the countershaft gears to move it the rest of the way out.  My guess is removing the shaft will require shifting a tight press fit gear- which I've already tried using as much force as I'm comfortable applying- no luck.  So, I'm going to punt and try an in-situ repair as follows;

The plan is to bore out the old bearing and shrink fit a new one in its place.  The bearing OD is 1 3/4", length is 3".  I'm going to use a 1 1/2" ID bearing and fit a matching collar over the scored shaft.  Thankfully, a 1 3/4" OD, 1 1/2" ID bearing is standard so that should go easily enough.  I have a length of 1.5" OD 4130 tubing- which I'll use if I can get a good fit into the bearing and onto the shaft.  If not, I'll bore out a length of ground 1.5" O2 drill rod.  In either case, the plan is to silver-solder the collar over the damaged portion of the shaft. 

Success will depend on getting a good collar alignment off the damaged shaft.  If I can't get an alignment I like, then I'll have to try something else.

March 28, 2005

I finally got the worn part of the bearing bored out and a sleeve turned and polished to provide a snug running fit on the bearing and a slip fit onto the shaft.  Its too late tonight to fit and solder it to the shaft, but I'll give it a whirl tomorrow.  The smudge visible on the bearing surface below is oil, though you can see I suffered from chatter on the interrupted cuts.  I had to take off .040 or so to make the bearing cylindrical again, about 1.432 ID.  The sleeve is a length of 4130 tubing I bored, turned and polished- its about 1.370 ID.

;;; eof