Tailstock restoration

[rwdenney]

My 1946 South Bend lathe's tailstock has issues. The lathe itself was restored in the past, probably by it's first owner (Bethlehem Steel, in the electrical department of the Sparrow's Point steel plant in Maryland). The ways were reground and the carriage was re-elevated using bronze shims screwed to the carriage (these days we would have used Turcite). That was done very accurately and the carriage motion is excellent. Facing operations are precisely correct and the headstock alignment seems correct with respect to the carriage.

But the tailstock is a mess. They restored the center height using galvanized sheet metal that is 0.114" thick between the tailstock baseplate and the tailstock body--in the interface normally used for shifting the tailstock side to side to align the centers horizontally. I figure it was 12-gage sheet metal that was made thicker by galvanizing. Of course, that is not a precision material and the thickness varies by a thou or two over its surface.

The main issue isn't the height, even though it's about 0.004 too high--that small amount too high won't introduce much of a taper for longer parts at least. The issue is that the quill is no longer in line with the ways when the center is centered. The tailstock center will shift laterally 10-15 thou over the extension of the quill, and a precision drill rod in the chuck is out of parallel with the ways by an even greater amount. (Some of that could be the chuck, but it happens with two different chucks--a Jacobs keyed chuck and a Cushman keyless chuck.)

One thing I'm thinking of doing is installing Turcite on the way surfaces of the tailstock base, and then getting rid of the shim. I can wiggle the tailstock in rotation when the lateral adjusters are loose, and my next move will explore whether the alignment shapes in the castings are being defeated by the shim.

For hole-drilling, I can use a tool holder with a morse taper to mount a drill chuck and align it as needed. But I do need a center than is, well, centered to avoid turning tapers.

Any ideas?

Rick "just starting to think about this" Denney

 

[Nutfarmer]

Sounds like the tail stock was not scrapped in properly after the bed was ground. Normally not an issue. You know where it needs to be. A good project to practice scraping.

 

[WesPete66]

If these shims are removable, why not recreate them in bronze? Nothing lost but your effort if you can't make a better shim. Interesting that they chose to put the shim in the interface and not at the base of the tailstock, like was done on the carriage. Seems to me the base would be the better place. Will Turcite handle the clamping forces of the tailstock clamp?

 

[rwdenney]

If these shims are removable, why not recreate them in bronze? Nothing lost but your effort if you can't make a better shim. Interesting that they chose to put the shim in the interface and not at the base of the tailstock, like was done on the carriage. Seems to me the base would be the better place. Will Turcite handle the clamping forces of the tailstock clamp?

That’s a good question. I’ve never worked with Turcite—only seen it done by guys like Keith Rucker.

I’m going to experiment with the horizontal alignment of the tailstock without the shim, and if I can get that to work, shim up at the ways.

I think the shim above the tailstock base was a shortcut—maybe whoever rebuilt the lathe didn’t use the tailstock. The lathe came without the spindle sleeve for using a center in the spindle, so it’s been decades since anyone had a thought of turning between centers. I mount a center on a straight shank in a collet when I need a spindle center. That’s within a couple of tenths and is close enough for my uses.

If I do end up shimming the tailstock at the ways, I could use bronze there, too, if Turcite isn’t going to work for whatever reason. But Turcite is easier to buy in exact thicknesses.

Rick “straight and narrow” Denney

 

[Smithdoor]

My 1946 South Bend lathe's tailstock has issues. The lathe itself was restored in the past, probably by it's first owner (Bethlehem Steel, in the electrical department of the Sparrow's Point steel plant in Maryland). The ways were reground and the carriage was re-elevated using bronze shims screwed to the carriage (these days we would have used Turcite). That was done very accurately and the carriage motion is excellent. Facing operations are precisely correct and the headstock alignment seems correct with respect to the carriage.

But the tailstock is a mess. They restored the center height using galvanized sheet metal that is 0.114" thick between the tailstock baseplate and the tailstock body--in the interface normally used for shifting the tailstock side to side to align the centers horizontally. I figure it was 12-gage sheet metal that was made thicker by galvanizing. Of course, that is not a precision material and the thickness varies by a thou or two over its surface.

The main issue isn't the height, even though it's about 0.004 too high--that small amount too high won't introduce much of a taper for longer parts at least. The issue is that the quill is no longer in line with the ways when the center is centered. The tailstock center will shift laterally 10-15 thou over the extension of the quill, and a precision drill rod in the chuck is out of parallel with the ways by an even greater amount. (Some of that could be the chuck, but it happens with two different chucks--a Jacobs keyed chuck and a Cushman keyless chuck.)

One thing I'm thinking of doing is installing Turcite on the way surfaces of the tailstock base, and then getting rid of the shim. I can wiggle the tailstock in rotation when the lateral adjusters are loose, and my next move will explore whether the alignment shapes in the castings are being defeated by the shim.

For hole-drilling, I can use a tool holder with a morse taper to mount a drill chuck and align it as needed. But I do need a center than is, well, centered to avoid turning tapers.

Any ideas?

Rick "just starting to think about this" Denney

I have done some repairs on tail stocks .
You need check if quill needs to be place. At same time check the barrow it may have taper. If so rebore the barrow and machine the quill to fit.
The in the tail stock ream morse tapper so accurate.

The screw thread is also damage a standard tap will work just machine both.
South Bend use acme and that cost more if want too.


Dave

 

[rwdenney]

Just for closure...

I ended up finding an old tailstock on ebay (and an old apron). Both are rather scarce for the 14-1/2 South Bend, but these were from a lathe being parted out by a used equipment dealer. Price was acceptable to me notwithstanding shipping costs that took my breath away.

When I pulled the top of the tailstock off the base, my heart sank--rust everywhere. And I set it aside for a while and thought dark thoughts. But I went back to it and spent some quality time at the wire wheel after taking it apart. Turns out, the rust was just superficial and the parts cleaned up very nicely.

Putting it on the lathe, I measured everything carefully and though it was about .020 low on center, it was dead straight in line (if the quill is locked) and stayed that within a thou as the quill was extended. I installed it on the lathe again with four pieces of .020 brass shim stock under each corner, between the base and the top. Unlike the old tailstock, raising it twenty thou had no effect on the directional tightness even when the nut was loose. The alignment screws were in a lot better shape, too.

At some point, I'll make careful brass shims in place of my quickies and call it done.

The apron is now on the bench. I need to install it to see how well aligned it is and if it corrects some of the minor defects in the current apron. (I know it corrects one defect already--the old apron has a slightly bent shaft on one of the driving gears in the power feed.) It's dirty but not really dirty and all the felts are in place and drawing oil as they should. I may just do a quick cleanup and install the thing to see how well it runs.

Rick "having spare parts is no bad thing with a 78-year-old lathe" Denney