Bearing Adjustment

I recently acquired a SB 10k. I am in the process of disassembly/ cleaning it. I have the book on renovating the 9, 10k which everyone recommends and it has really helped. I've been hesitant to ask this because I've been unable to find any type of reference to it which usually means, at least in my experience, that the answer is so obvious no one has ever bothered writing it down.
So here it goes... I am getting ready to tackle the headstock. All the youtube videos, SB literature, this forum and even the book I am using state that when you are determining what adjustment the bearings need, to pull up on a bar inserted through the spindle with a force of 75 lbs but none of them explain how you know when you reached 75lbs. In other words, I wouldn't know 75 lbs force from 175 lbs force other than one is more than the other. Is there some type of measuring device that would indicate that similar to a torque wrench??

Tie a scale onto the bar and lift. When did mine I just guesstimated. You will probably find that the indicator will either move a lot or not at all.

Interesting to note that I have a 4 jaw chuck that came with mine that I think is original and I swear it weighs ~100lbs. I am going through mine too. If you want to be super close you might stand on a bathroom scale and add or subtract your body weight. I suspect if you are close you will be doing it right!

I doubt you can lift 175 lbs, so we don't have to worry about that

The amount is not particularly critical, so no need to get out a scale. Just imagine you are lifting 10 gallons of water.

allan

Tearing down be certain you that you place shims in a way that you can put them back to the exact same place.
Knowing both sides are getting oil, and being in spec (I think less than .002 cold) I would not tear it down.

Shims can seem to hide by sticking to one cap and the all of a sudden you may not be sure each came from.

A bar perhaps 18" out and a hand lift should not be difficult.

likely I would let it go to .0025 cold before messing with it... then shoot for .0015.

Thin shims can stick together so micrometer measure each shim stack and map where they go.

Perhaps just cleaning up bugs may get you the fit you are looking for.

Mark the caps to put back the same place and way. Holes are deliberately made of/odd so they only fit the right place and way.

Guess first I would feel the bolts with a torque wrench to find all at perhaps 15 pounds. Likely they have a torque specification..you might look that up.

MeanMachine1980 said:

Tie a scale onto the bar and lift. When did mine I just guesstimated. You will probably find that the indicator will either move a lot or not at all.

Click to expand...

Kevin T said:

Interesting to note that I have a 4 jaw chuck that came with mine that I think is original and I swear it weighs ~100lbs. I am going through mine too. If you want to be super close you might stand on a bathroom scale and add or subtract your body weight. I suspect if you are close you will be doing it right!

Click to expand...

I knew the answer would be that simple. I never thought of a scale. Just moving the bathroom scale to the garage is about as simple as it gets. Thanks.

kitno455 said:

I doubt you can lift 175 lbs, so we don't have to worry about that

The amount is not particularly critical, so no need to get out a scale. Just imagine you are lifting 10 gallons of water.

allan

Click to expand...

Well, there was a time many years ago when I could

michiganbuck said:

Tearing down be certain you that you place shims in a way that you can put them back to the exact same place.
Knowing both sides are getting oil, and being is spec (I think less than .002 cold) I would not tear it down.

Shims can seem to hide by sticking to one cap and the all of a sudden you may not be sure each came from.

A bar perhaps 18" out and a hand lift should not be difficult.

likely I would let it go to .0025 cold before messing with it... then shoot for .0015

Click to expand...

Thanks for the advice. I had debated not messing with it since it is the most critical part of the lathe and I could mess it up. On the other hand, you just dont know what you're gonna find on a used piece of machinery. I have completed the disassembly/cleaning/reassembly of the quick change gear box and I am about 50% done with the apron. On the gear box, the gear on one of the tumbler levers would not turn freely so I had to replace the needle bearing. There was also something in the oil reservoir that was preventing oil from going to the ports on the left side. The apron was just filthy. The oil drain port was blocked with shavings etc. If anything, disassembling it has helped me understand how it all works. If I can convince myself that everything is ok with the headstock, I still may not mess with it.

The clearance measurement is:

1) pull up on the broomstick in the spindle bore.

2) zero the dial gage

3) push down on the broomstick

4) then read the TIR of the bearing clearance.

The pulling and pushing is for one reason only - to overcome the oil film resistance to get
an accurate clearance reading. The oil will tend to center up the spindle in the bore of the bearing.

You know you have applied enough force, when the dial gage reading stops changing.

I should add to avoid false readings you should fix the indicator to the headstock casting...otherwise you can potentially get movement from other sources...EVERYTHING is made of rubber and even the headstock bed clamps can and will flex.

jim rozen said:

The clearance measurement is:

1) pull up on the broomstick in the spindle bore.

2) zero the dial gage

3) push down on the broomstick

4) then read the TIR of the bearing clearance.

The pulling and pushing is for one reason only - to overcome the oil film resistance to get
an accurate clearance reading. The oil will tend to center up the spindle in the bore of the bearing.

You know you have applied enough force, when the dial gage reading stops changing.

Click to expand...

I have not seen that explained before. I had wondered why the procedure was to push down... to account for the oil film. Thanks for that.

Besides the ambiguous force is the ambiguous distance at which we apply the force. 75 (?) pounds at how many inches from the headstock???

jim, kitno455 and iwananew10k have the right deal to guide you right.

John

Adam,
Re-read the last statement in Jim's explanation, Front bearing: Mount your DI on the compound base and indicate close to
the bearing on the spindle. Push down on the bar until the DI does not move any more, note the pressure you feel to reach
this point and the reading, this is the oil film limit. Now pull up on the bar until the same indicator does not move in the upper limit. Note the reading. Subtract for total clearance measurement. Bronze shell bearings are 0.0007 to 0.001. Each time you make an adjustment of shims, you have to back the expanders off first, then after adjustment tighten the expanders before doing the lift test again or you will damage the shells. The oil film clearance is subject to the spindle oil viscosity. South Bend's recommended numbers are for the spindle oil viscosity specs they specified. This insures that you get the correct oil film wedges to lift the spindle in operation to hydroplane. The lift pressure is only related to the amount of force required to see the film limit on the indicator.
On the rear bearing mount the indicator on the quill guard and close the outer bearing on the spindle, run same test. Adjust the front bearing first and remeasure before moving (testing) to the rear.

Steve