Lathe tail piece problem

I have a 13 inch Sheldon lathe. I notice it has a little back and forth play in the barrel in the tail piece. I do a lot of drilling and I want accurate holes. I have two questions, One, is there anything I can do to improve the accuracy? Second, if I keep the handle that locks the barrel so it won't move a little snug so it stops the wobble and just off set the tail piece to dead center would that be a salutation? Should I try to find another tail piece? Seems like it would be hard to find? Thanks

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Snugging the lock is likely your best solution, so if it works for you, I'd suggest you stick with it. The wear you have in your machine will not be uniform, so changing the quill would likely not fix the problem, although it might be slightly different. The permanent solution would be to buy a new machine, which is hardly an acceptable fix for most of us.

You mentioned you want accurate holes. Drilling isn't exactly a precision operation, even when followed by reaming. If you want accurate holes, I'd suggest you bore them, not just drill them. If you aren't comfortable with holding size, you might consider drilling undersized holes, boring them to put them dead on location, still a few thou undersized, then open the hole with a chucking reamer held by a tiny amount on the end of the shank. That way you should end up with a reasonably straight and round hole.

The other thing you can do to improve accuracy of drilled holes is to step drill them. Start with a spotting drill or a center drill, drill undersized by about .015", then open the hole to your desired size. That will generally yield a pretty decent hole, but not as good as a reamer of a boring bar.

Good luck


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Harold & Susan Vordos

That's the usual method.

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Richard J Kinch (Cuezilla) wrote in news:376f0f2e.0402021120.7b4db980

You can disassemble the tailstock, bore out the housing, insert a new bronze sleeve, and rebore/ream to the proper size, or live with it. There are companies that do this type of repair also.

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You neglect a lot of information. I offer a pathway to discover where your problems lie.

First, mike the spindle; determine if it is uniform in OD. My ancient Southbend quill is very uniform in size, but the hole in the casting is not. Why wear on the casting and not the quill ? I have no idea!

Second, Using "T" gauges, measure at several points the diameter of the hole on the casting. If the hole is tapered, you will have to bore it straight and make a new spindle. If the hole is straight, and the quill is small enough to rattle, consider making a new quill.

Third, using a dial gauge fastened in the headstock chuck, determine if the hole in the tailstock casting is on center-line. Rotate the chuck by hand with the dial indicator riding on the outside of the tailstock quill. Clamp the quill tightly, and check again. You might check against the inside of the casting as well. You might find that the casting has worn low towards the headstock, resulting in the quill pointing down towards the chuck instead of being parallel. Look at the saw slit used with the quill clamp(if your lathe uses a saw slit, some used a different method to clamp). When it was new, the slit was nearly constant in width when the quill was clamped, because there was little slop between the quill bore and the quill.

You will need to know the information above if you take your tailstock casting to someone to rework. ESPECIALLY you will need to know if any part of the casting, say the back towards the crank is concentric and on center height. This can be used as a reference height when making the bore larger.

If you are boring small holes, I would consider building a quill which takes collets to hold the drill bits, and using a lever to advance the drill.

Quill making is not casual, because of the concentricity and dimensional accuracy required. You will need to have dead centers, a center rest, a morse taper reamer, and preferably, a tool post grinder. If you are going to try to turn all your dimensions, start with piece of leaded steel (12L14 comes to mind) so you can get good finishes without stressing your old lathe. Make the morse taper hole, and then turn the outside concentric with the hole using dead centers. (Kinda like making a gun barrel in the old days). I find it easier to make a brass plug screwed into the rear of the quill with the square threaded left-hand thread (for the feed screw) cut into the brass, rather than trying to cut the thread in the quill itself. This allows me to change the thread when it wears out.

The easiest way to check a quill for accuracy of the taper is to turn a taper in the lathe that fits the tailstock, and WITHOUT TAKING THE TAPERED STUB OUT OF EH CHUCK WHERE IT WAS TURNED, plug the tailstock on, and check for runout. If the tailstock has been reamed too many times, the taper is not necessarily on center height and parallel to the quill O.D.

Enough chatter.... Brownnsharp

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Bronze works well for this, the cylindrical threaded nut can be secured with an off-center taper or roll pin. My experience with doing this involved a small pratt & whitney bench lathe, where the tailstock was one piece and had worn quite badly. After re-scraping the bottom of the tailstock to fit the ways, of course the hole in the casting was way too low - so I made a new ram with the mt1 hole offset the correct amount. I found that boring the starting socket for the taper while the ram was held in the lathe was pretty much the best way. Unless the hole is taper bored to start it's tough to get any kind of axial alignment between the socket and the ram.

I used a no.1 mt reamer, as little as possible, to clean up the bore and set the taper exactly right. No doubt if I had a toolpost grinder this would have been even a better approach to final sizing. But lacking that, the sequence of bore to set axial alignment, and finish ream does a passable job.


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jim rozen

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