Playing with my telescoping bore gages I got the following:
| Inches in from the end | Measurement plane | ||
| Horizontal | Vertical, unclamped | Vertical, clamped | |
| 0 | 1.626 | 1.628 | 1.625 |
| 1 | 1.626 | 1.625 | 1.624 |
| 2 | 1.625 | 1.625 | 1.623 |
| 3* | 1.623 | 1.623 | 1.622 |
| 4 | 1.623 | 1.622 | 1.622 |
| *- End of the clamp slit. | |||
On the other hand, the quill measured 1.622 in all directions--essentially unworn.
My final procedure was sort of an amalgamation of several responses and ideas, mostly from r.c.m.
First off, I bored out the housing. To do this, I first got a long (about 30" or so) 1" bar out of my scrap pile with at least some semblance of a spot at one end that could be considered sufficiently round to run in a steady rest. About midway down the bar, I drilled and filed a square hole for a 1/4" HSS bit, and crossdrilled and tapped it for a 1/4-20 setscrew. I clamped one end in the 3-jaw and set the other end up in the steady rest, with the tailstock between the bit and the chuck, clamped just enough to let it slide but not so loose as to let it hop or chatter.
I had run the carriage all the way up to the headstock beforehand. At this point, I then fired up the spindle and engaged the feed outward, and let the carriage simply push the tailstock base along the ways towards the steady rest. I had just enough boring bar length to access the cutting bit with the tailstock at either end. I then slowly added extension on the cutting bit until it started to clean up, and continued until I had it oversized--I forget now exactly by how much, but it was probably on the order of .050 or so over the quill size. The last pass I made with the gears setup to thread at about 4 tpi to leave a spiral groove, in the hopes of getting a better bond with the epoxy.
Ideally, I'd have used Moglice. But probably due to a flaw in my character, I just couldn't see spending the cost of 2 fluid ounces of it (I think its about $100/oz) to fix this beast, so I found something which pouring over the physical property specs led me to believe was vaguely similar: Devcon Plastic Steel Liquid, which I ordered from MSC.
It took me a while to gather my courage for the last step, even after I'd found the "tuit" (oh look! a round one, even!). I drilled three holes in the top of the tailstock down into the quill bore, and rubbed several coats of paste wax onto the quill. I filled the clamp slot with plasticene. Using a toolpost mounted drill chuck (what I've been using to drill with once I figured out the tailstock was worn), I centerdrilled a stub of 1" rod held in the 3-jaw. Stuck my live center in the quill, set the quill in the bore, and slid the whole tailstock up until the livecenter was against the centerdrilled mark. I put more plasticene around the back of the quill (though in 20-20 hindsight, probably not nearly enough) and reassembled the quill screw and handwheel to hold up the far end.
I put on a pair of rubber gloves and mixed up the epoxy (note: a pound of liquid steel is only about 5 or 6 fluid ounces! I'm glad I only needed about 2 for this repair!). I was very glad to see that the thin runny hardener diluted the very thick base epoxy down to the point where it could actually be considered a liquid--I had some doubts when I first started spooning it out of the container. Once mixed, I spooned the mix into a 2oz. irrigating syringe and jammed the tapered end into the rearmost of the 5/16" holes I'd drilled in the tailstock housing, and slowly pushed down on the plunger. When I saw epoxy start to come up out of the middle hole, I breathed a big sigh of relief--I wasn't sure if it was going to be thin enough to fill into the gap until then. I switched to the hole at the chuck end, and pressed down on the plunger again until I saw epoxy running out of the gap between the quill and the end of the casting. Then I went back and refilled the syringe and pumped a little more into the middle hole until I saw epoxy rising out of the other 2 holes. I had most of a syringe left over. I wiped up what I could of the excess epoxy and let it sit. The rest of the contents of the syringe I pumped out into the hardener bottle (since it was smaller) and tossed the syringe.
Working time for liquid steel is listed as about 45 minutes. During this time, I kept checking back on it, and either it was settling, shrinking, or air bubbles were rising, but the end result was that the level in the holes was dropping, so I kept stopping back and scooping a little more out of the mixing tray (piece of milk carton) with the plastic spoons I'd mixed with to top them up. After about an hour, it was noticably setting up, and you could smell the epoxy working, and the hardener bottle full of the leftover epoxy was warm from the chemical reaction. I then left for work.
Once I returned from work that evening, I disassembled the leadscrew and handwheel from the housing. In the course of doing that (a few turns on the end bell one way, a few turns on the leadscrew the other) I eventually got enough pressure on the quill to get it to break free and move. Once the end bell was all the way off I could see in the back end of the quill inside the housing--and saw where some of the "extra" epoxy had gone. There is a keyway along the bottom of the quill, and it looks like the pressure built up enough in the keyway that the epoxy shot out under the plasticene and filled the space between the end bell and the quill about 1/4 full. Fortunately, the leadscrew and end bell were sufficiently oily that the epoxy didn't stick to them, but I still ended up chipping out the rest with a small cold chisel.
Once I had clear access to the back of the quill, I cut a wooden plug to go over the back of it, inside the housing, and tapped on it with a hammer. It barely moved. I worked up to about a 2lb. hammer before I could get it to reliably move, and then added a chunk of 1" rod once I had pounded the wood in out of reach, and so drove the quill out of the housing. Inspection showed only one place the epoxy didn't fill completely, which is about a 1" square section opposite the clamp slot. The rest was nearly glass smooth. I cleaned up the quill and worked it back in with a pipe clamp, and then drove it back out again. It got slightly easier each time, and after doing the in-out cycle twice, I called it close enough and reassembled it. It still takes quite a bit of effort on the handwheel to get the quill to move.
Having gone through this, I think I may have learned enough about the technique to make a few observations. If this were a more valuable machine, I'd have no qualms about using the proper epoxy. I think doing this with a real slideway product like Moglice would be better than the liquid steel, and probably worth the extra expense, just for the reduced effort to get the quill to move once everything has set. Were I to try to use the liquid steel again, I think I'd try to get a few more layers of wax on the quill in the hopes that it wouldn't be so tight. And I'd use more plasticene to try and get better control of where the epoxy goes.
While I have yet to try turning something between centers, I have every confidence that any problems I might have with doing so won't be coming from the tailstock, but with my own technique. All in all, I'm glad I finally bit the bullet and finished this repair. Now I just have a stripped back gear and a missing rack tooth to contemplate repairing...
Last updated 10/21/06
© 2006 Glenn S. Lyford, all trademarks etcetera property of their respective owners.