Old lathe spindle setup

[PIngels]

Hello all,

since I got the minilathe I have always wished for a bigger and especially more rigid lathe. That I found a couple months ago, and I bought a very old lathe for near nothing.

I have it now torn down, painted and am about to build it back together.

However I have a small problem with the spindle assembly: it was turning smootly before teardown but now I just put everything in place it's binding when I screw everything together.
It is an old type assembly: bronze bearings, just one thrust ball bearing in the back.

Is there a special procedure and things I have to check out to get such old bronze bearings back adjusted finely?
What are the locking rings for, they seem to have no effect. Any help will be greatly appreciated.


Plan is to try to retrofit it to CNC later on, but I would really like to have it running as is first

Here are some pictures of the work in progress.

Thanks
Pierre

[NC Cams]

If the head and or bed were twisted and the machine ran itself in that way, if you reassmbled it w/o the twist/bend/whatever, you may have gotten the axis of rotation askew.

The think may want to be tightened down in a certain sequence or to a certain special torque - over or uneven torquing might cause sticking and binding.

Sometimes, old sleeve bearing stuff should not be disturbed for these very reasons. You're gonna have to take your time and do some experimenting to nudge caps this way or that and try to find the sweet spots where things will be properly tightened and yet the thing will still turn.

That or else line bore the housing straight/square and grind the spindle journals to the proper fit/clearance as well.

Time and patience, time and patience, with the situation you're in....

[Geof]

Sometimes on those old lathes there are shims under the bearing caps. These are used as a crude way of adjusting for wear on the bronze. If you release the bolts slightly does it stop binding, if yes I suggest simply experimenting with shims to see if you can get it running freely but without excessive clearance. Coke cans make good shim stock.

[miljnor]

Coke cans make good shim stock.

And it comes with a very good throat lube!

[NC Cams]

Smooth aluminum foil works well too - more consistant thickness if you use the non-quilted stuff. Exacto knife cuts it just fine.

[Adobe Machine]

Go to your local "we sell anything" auto supply store and purchase 2 feeler guage sets, minimum .0015 to at least .020. They are not expensive, cheap.
clean and remove any shims, or any trash, clean shaft and bearing housings.
Unload the belts and back gear. Assemble bearings with a light lube ( 30 wt oil). Do not tighten bolts, start with the smallest ( thinnest ) feeler guage, same on each side of the bearing housing. Lightley tighten the bolts and see if it begins to lock up, if so keep adding feeler guages ( same both sides) untill the shaft turns freely, tighten to the lathe torque specs( should be around 45-50 lbs ) if still free ( should have some drag), remove and clean the bearings and install one of the final feeler guages under the bearing (one only),Tighten to specs.You should have about the same drag as before, then install the belt , again check for binding, engage the back gear and recheck.
These are most likley hand scraped, poured, babbit bearings,which is almost a lost art, so make sure the lube wicks are in place, the lube ports are clean and free of debri. If you correctley shim, there should be some heat on the bearing housing when tested , not excessive. Give the bearings time to bed in, then start cutting..After a couple of hours , check the run out of the chuck end, may be loose, so add a thicker shim in .001 increments.
There are a lot of those old lathes that have very little , if any run out ,provided the chuck end bearings are correctly shimed.This just takes time, but is the difference between a boat anchor and a good home shop lathe.
Correct lubercation can not be over emphasized.
(hey, don't laugh, I'm old enough to have done just a couple of these)

Adobe (old as dirt)

[Adobe Machine]

Forgot to mention,before any shimming is done, make sure the lathe and bed are leval...leval before trying anything..Like NC cams says, any twist will affect the the head stock..You will need a good machinest leval and the proper procedure..just another thing that takes a lot of patience..

Adobe (old as dirt)

[Geof]

And even if you end up with a lot of slop you can still turn to quite good tolerances. The spindle is so heavy that it rides on the bottom bearing when you are taking a final sizing cut because the cutting load is so light. And if you want to take heavy cuts without the spindle bobbing up and down in sloppy bearings you just mount the tool upside down and run it backwards.

[Adobe Machine]

Geez, you guys are super, never thought about that..! But your right, the spindle would be forced down..Damn and I thought I had done everything with an old wore out POS to make accurate cuts.. Must be the long winter nights in Canada ..

Adobe (old as dirt )

[Geof]

... Must be the long winter nights in Canada ..

Adobe (old as dirt )

It was actually long warm days in New Zealand where I served my time and for around nine months of it ran an ancient lathe with overhead belt drive and sleeve bearings a tad bigger than this one. Making hundreds of brass sleeves that I think were used in the tracks of big excavators.

[PIngels]

Thank you so much for your help!

I'll arm myself with patience and try to do that well

[RICHARD ZASTROW]

AM, Ref. Geof's #8 This has also been done on CNC lathes. The product was large forming rolls with deep grooves that had radiused bottoms. We used a 3/16" carbide button tool upside down on a modified toolholder; ran the machine backwards. The hydraulic clamping of the tool turret acted as a hydraulic vibration damper. Worked fine.