Worn out tailstock repair options...?
Hi,
I've noticed that I haven't been getting much support from my tailstock when turning longer items, so I set up an indicator to measure just how much support I wasn't getting, and found that at 4" extension, the end of the ram could move .012 with hand pressure, unclamped, .010 clamped. Retracting to 0" extension, I could move it about .004", clamped. In both cases, I was measuring front-to- back, but imagine the vertical number would be similar. Adding washers under the clamp handle had no effect. Now the remedy: If this were something common like a Southbend, Logan, or Monarch, I'd just try to track down another tailstock. It's a 14" Hendey, 1890's vintage. Probably not going to happen, so probably best to try to repair what I've got. Removing the ram and playing with a mic, I get 1.622 diameter everywhere I measured it. I haven't measured the bore yet. I just got some telescoping gages, so will have actual numbers on that later. My options as I see it a 1. Bore out the tailstock and make a new ram. Probably the simplest option, as the ram itself is fairly simple, 9-1/8" long, 1-5/8" diameter, MT3 socket, LH acme thread on the back for about an inch or two, one 1/8" keyway on the bottom, one oil groove on the top. Possible fly in the ointment: making the new ram without a good tailstock. I do have a steady, but I haven't used it yet. 2. Rebore and have the ram plated and reground. Sounds like this could get expensive in a hurry since I would have to have someone else do this. 3. Rebore and sleeve to fit existing ram. If I do this right, I may be able to bore out to fit standard tubing, pressfit or locktite in place (as I'm not experienced enough to trust my ability to get a good press fit on this), then rebore this insert in place to fit the ram? 4. Shim the clamp end of the tailstock bore with something like sheet brass or aluminum, locktited in place. A hack, if it would work at all. Which would you choose, and why? Are there others that I haven't thought of? (I can hear the rumble of "yeah, get a newer lathe" from the back, and while this may yet happen, it won't be soon). In most these cases, I am looking at reboring the tailstock. Would you expect being able to get anything approaching reasonable results with a boring bar held in a chuck and running in a steadyrest on the far side of the tailstock? The handwheel end of the tailstock casting looks like it doesn't come off, so that end of the bar would have to fit through the root diameter of the leadscrew, maybe 1/2", if that. I'd expect that rigidity could be a problem (understatement). At least the diameter from the chuck up to the cutter could be larger, possibly up to 1-1/2". Any other not-to-obvious gotchas? Thanks, --Glenn Lyford |
Glenn Lyford writes:
3. Rebore and sleeve to fit existing ram. I'm wondering if you couldn't turn the ram smaller, epoxy on Teflon or Turcite sheet, and turn that to the original bore size. That's how flat ways are rebuilt to original sizes, and the techniques aren't difficult. Might even improve on the original rigidity. |
In article ,
Richard J Kinch wrote: Glenn Lyford writes: 3. Rebore and sleeve to fit existing ram. I'm wondering if you couldn't turn the ram smaller, epoxy on Teflon or Turcite sheet, and turn that to the original bore size. That's how flat ways are rebuilt to original sizes, and the techniques aren't difficult. Might even improve on the original rigidity. You might be able to use Moglite? -- Free men own guns, slaves don't www.geocities.com/CapitolHill/5357/ |
Just wondering if you've considered or if anyone else has an experience with something like Brownell's Electroless Nickel plating. Plate it until the fit is tight again. Would seem like this would be a good application. Steve. "Glenn Lyford" wrote in message . .. Hi, I've noticed that I haven't been getting much support from my tailstock when turning longer items, so I set up an indicator to measure just how much support I wasn't getting, and found that at 4" extension, the end of the ram could move .012 with hand pressure, unclamped, .010 clamped. Retracting to 0" extension, I could move it about .004", clamped. In both cases, I was measuring front-to- back, but imagine the vertical number would be similar. Adding washers under the clamp handle had no effect. Now the remedy: If this were something common like a Southbend, Logan, or Monarch, I'd just try to track down another tailstock. It's a 14" Hendey, 1890's vintage. Probably not going to happen, so probably best to try to repair what I've got. Removing the ram and playing with a mic, I get 1.622 diameter everywhere I measured it. I haven't measured the bore yet. I just got some telescoping gages, so will have actual numbers on that later. My options as I see it a 1. Bore out the tailstock and make a new ram. Probably the simplest option, as the ram itself is fairly simple, 9-1/8" long, 1-5/8" diameter, MT3 socket, LH acme thread on the back for about an inch or two, one 1/8" keyway on the bottom, one oil groove on the top. Possible fly in the ointment: making the new ram without a good tailstock. I do have a steady, but I haven't used it yet. 2. Rebore and have the ram plated and reground. Sounds like this could get expensive in a hurry since I would have to have someone else do this. 3. Rebore and sleeve to fit existing ram. If I do this right, I may be able to bore out to fit standard tubing, pressfit or locktite in place (as I'm not experienced enough to trust my ability to get a good press fit on this), then rebore this insert in place to fit the ram? 4. Shim the clamp end of the tailstock bore with something like sheet brass or aluminum, locktited in place. A hack, if it would work at all. Which would you choose, and why? Are there others that I haven't thought of? (I can hear the rumble of "yeah, get a newer lathe" from the back, and while this may yet happen, it won't be soon). In most these cases, I am looking at reboring the tailstock. Would you expect being able to get anything approaching reasonable results with a boring bar held in a chuck and running in a steadyrest on the far side of the tailstock? The handwheel end of the tailstock casting looks like it doesn't come off, so that end of the bar would have to fit through the root diameter of the leadscrew, maybe 1/2", if that. I'd expect that rigidity could be a problem (understatement). At least the diameter from the chuck up to the cutter could be larger, possibly up to 1-1/2". Any other not-to-obvious gotchas? Thanks, --Glenn Lyford |
Glenn Lyford wrote in
: Glenn, The way our production machines are repaired, is to grind enough stock off of the quill to clean up any wear, then bore, sleeve and rebore the tailstock housing. -- Anthony You can't 'idiot proof' anything....every time you try, they just make better idiots. Remove sp to reply via email |
In article , Glenn Lyford says...
Removing the ram and playing with a mic, I get 1.622 diameter everywhere I measured it. I haven't measured the bore yet. First off you should be *absolutely sure that the clamp mechanism is functioning the way it should. Some of them clamp via a slit alonside the casting, so that the clamp bolt actually tightens up the bore. There are others that have a two-piece clamp that self-centers in a vertical hole, and pinches the ram. What kind of setup does this Hendy have? My experience is that the bores and the rams wear at about equal rate. So finding the ram dimension constant along its length implies to me that the bore might be OK. The amount of slop that you see when the clamp is snugged down is pretty large - large enough to imply to me that something is wrong with the clamp setup. If the bore really *is* bell-mouthed then you probably need to worry about opening it up and fabricating a new steel ram. This is not trivial to do, as you need to get the MT socket in the center of the ram to be right on axis, on both planes. Boring the tailstock casting is tough because of the rigidity issues you mention. Plus you want to take as small a cut as possible of course, so the bar is subject to chatter. I think it would be informative to figure out how those bores are formed in the first place. I wonder if a reamer would provide an accurate enough hole - would it follow the existing hole axis close enough, and cut to size even though the existing hole is bell-mouthed? Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Nick Hull writes:
You might be able to use Moglite? Casting Moglice doesn't seem appropriate for this closed geometry. Applying and machining Teflon or Turcite is relatively simple by comparison. |
On 11 Dec 2004 10:14:13 -0800, jim rozen
wrote: In article , Glenn Lyford says... Removing the ram and playing with a mic, I get 1.622 diameter everywhere I measured it. I haven't measured the bore yet. First off you should be *absolutely sure that the clamp mechanism is functioning the way it should. Some of them clamp via a slit alonside the casting, so that the clamp bolt actually tightens up the bore. There are others that have a two-piece clamp that self-centers in a vertical hole, and pinches the ram. What kind of setup does this Hendy have? My experience is that the bores and the rams wear at about equal rate. So finding the ram dimension constant along its length implies to me that the bore might be OK. The amount of slop that you see when the clamp is snugged down is pretty large - large enough to imply to me that something is wrong with the clamp setup. If the bore really *is* bell-mouthed then you probably need to worry about opening it up and fabricating a new steel ram. This is not trivial to do, as you need to get the MT socket in the center of the ram to be right on axis, on both planes. Boring the tailstock casting is tough because of the rigidity issues you mention. Plus you want to take as small a cut as possible of course, so the bar is subject to chatter. I think it would be informative to figure out how those bores are formed in the first place. Now that's a good question ! I had mine nickel plated twice and ready to lightly polish in the other lathe , haven't got around to that part yet , but it holds tight now backwards. It has a slit on the back side like Jim said above and from the same era as yours. If you bore it out I'd like to see pictures of the set up and how the TS is driven. I've thought about doing it that way , but I don't think my lathe is really worth the trouble. Hmmm , bolt the carriage and TS together and a SR. Still , the ram would be hard to remake. I wonder if a reamer would provide an accurate enough hole - would it follow the existing hole axis close enough, and cut to size even though the existing hole is bell-mouthed? Jim |
I vote for building up the worn part with hard chrome and having it
cylindrically ground to size. - GWE |
In article , Grant Erwin says...
I vote for building up the worn part with hard chrome and having it cylindrically ground to size. - GWE But the ram is not worn. It has constant diameter over its whole length. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
Glenn Lyford wrote:
.... Now the remedy: If this were something common like a Southbend, Logan, or Monarch, I'd just try to track down another tailstock. It's a 14" Hendey, 1890's vintage. Probably not going to happen, so probably best to try to repair what I've got. .... From the other replies it seems as though your repairing this one might be kinda tricky. Maybe you should reconsider a replacement, but with a twist: how about adapting a SB, Logan, whatever to your lathe. Get a slightly smaller one and machine a plate adapter. It seems to me that the machining would be less demanding. Not that I've ever done this, so maybe somebody else can comment. Bob |
jim rozen wrote:
In article , Grant Erwin says... I vote for building up the worn part with hard chrome and having it cylindrically ground to size. - GWE But the ram is not worn. It has constant diameter over its whole length. Jim Perhaps the implications of increasing the tailstock ram diameter by plating slipped by? Common practice would be to rectify the tailstock housing and plate & grind the ram to suit. Tom |
jim rozen wrote:
In article , Grant Erwin says... I vote for building up the worn part with hard chrome and having it cylindrically ground to size. - GWE But the ram is not worn. It has constant diameter over its whole length. OK, Jim, I know you are no dummy. What *is* worn? If you have a funky worn bore in your tailstock body then I vote for boring and resleeving. If the bore's OK but the ram is worn then I vote for plating and then regrinding. Tricky, that, because you don't want to plate the ID taper .. Grant |
In article , Tom says...
But the ram is not worn. It has constant diameter over its whole length. Perhaps the implications of increasing the tailstock ram diameter by plating slipped by? Common practice would be to rectify the tailstock housing and plate & grind the ram to suit. The hard part is repairing any out-of-round condtion in the bore of the casting, IF there is any. Because this has yet to be measured, I have to withhold any other suggestions. But to reply to your point, I guess I would fabricate an new ram from scratch, rather than chrome the old one. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
From the other replies it seems as though your
repairing this one might be kinda tricky. Maybe you should reconsider a replacement, but with a twist: how about adapting a SB, Logan, whatever to your lathe. Get a slightly smaller one and machine a plate adapter. It seems to me that the machining would be less demanding. Not that I've ever done this, so maybe somebody else can comment. OK, I've heard of others doing this too. And I'd still have the original tailstock to play with, too... --Glenn Lyford |
Removing the ram and playing with a mic, I get 1.622
diameter everywhere I measured it. I haven't measured the bore yet. OK, playing with my new telescoping HF bore gages I get the following: Inches ===== Measurement plane ===== in from Horiz. Vert., Vert., end unclamped 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. Some of them clamp via a slit alonside the casting, [...] What kind of setup does this Hendy have? The slit type, not the two-piece type. If the bore really *is* bell-mouthed Numbers pretty much say it is. I think it would be informative to figure out how those bores are formed in the first place. Took another look at the assembly, and there is a hole on the bottom side of the bell end where the handle attaches. A blind hole. A spanner hole. Ten seconds later, the entire handwheel and end bell assemble is loose in my hands, and I'm looking through a large bore, straight through the tailstock. _Much_ better! Now I can go way up with my boring bar ability. The only possible concern here is the threads for the end bell are directly in the tailstock bore, so I'd have to stop whatever process I use short of mangling those threads. I wonder if a reamer would provide an accurate enough hole - would it follow the existing hole axis close enough, and cut to size even though the existing hole is bell-mouthed? Enco has an adjustable reamer that goes up to 1-13/16ths for $35. Since I don't have to worry about end-bell clearance, an adjustable would work, and it looks like the majority of hand and chucking reamers stop at 1-1/2. But I would expect boring would give me a more accurate hole should the wear not be even front-to-back or top-to-bottom, whereas the reamer would follow the hole as worn, yes? --Glenn Lyford |
Richard J Kinch wrote:
I'm wondering if you couldn't turn the ram smaller, epoxy on Teflon or Turcite sheet, and turn that to the original bore size. That's how flat I've never used Turcite so can't comment on that but I've done lots with Teflon. Teflon will cold flow so doesn't work well anywhere significant pressure is involved. UHMW polyethylene would be much better in this application. Ted |
Ted Edwards writes:
Teflon will cold flow so doesn't work well anywhere significant pressure is involved. Despite this oft-heard glib dismissal, plain Teflon (PTFE) works well for reconstructing machine tool ways. "Cold flow" is a misnomer. The phenomenon is properly called creep, an odd mechanical property where the yield strength for plastic deformation is a function ot time. But for PTFE, this is still only significant only at 1000s of psi, which is not present in ways. Machine tool bearing surfaces do not typically exceed more than a few 100s of psi transiently, and much less statically. This is by design to ensure rigidity and lubrication. This makes them good candidates for PTFE rebuilding. Indeed, machine ways are carefully designed to ensure that forces are never concentrated anywhere on the bearing surfaces. The same principle fits PTFE properties quite well. |
In article , Richard J Kinch
says... Machine tool bearing surfaces do not typically exceed more than a few 100s of psi transiently, and much less statically. Except for the clamping action of a the tailstock casting on the ram. I would say that pure ptfe is a poor choice for that application. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
jim rozen writes:
Machine tool bearing surfaces do not typically exceed more than a few 100s of psi transiently, and much less statically. Except for the clamping action of a the tailstock casting on the ram. I would say that pure ptfe is a poor choice for that application. If you mean the narrow longitudinal strip of the ram which is engaged by the clamp, yes, you would leave that as bare metal. It's not a bearing surface anyway. Note that with a polymer bearing surface, you could create a negative clearance on the ram vs bore. This would eliminate both play and stiction, which are typically why you need a clamp at all. |
If you have a saw slit with a clamp screw which clamps the quill, you
should measure the width of the slit at a point away from the clamp screw, towards the back of the tailstock. Whatever this dimension is, put a shim in the slot near the mouth of the quill with that dimension, and clamp on the shim. The hole will then be near the original size. Now the "T" gauges will measure the hole diameter correctly. If it is off, then bore the hole out to get parallelism and ensure EXACT center height for the hole. Using the new bore dimensions, make a new quill. Make the quill with steps in this order. First bore a through hole in a piece of steel which is the root diameter of the thread at the back of the quill. Thread the hole to match the screw. Put an accurate, 60 degree chamfer to match a dead center around the perimeter of the threaded hole. Turn the quill blank around and bore the hole to the small diameter of a dead center (2 morse taper, or three morse taper or whatever). Using the center rest, bore the morse taper to match a test taper. If you can get a finish reamer, use it to get the final taper perfect. Insert a dead center in the taper, and mount the quill between this dead center and another in the taper at the threaded end. Turn the OD to match the hole in hole in the tailstock casting. The weapon of choice here is a post grinder if you have one. If you have done everything correctly,. the hole in the taper will be concentric with the outside of the quill, and the hole in the tailstock casting will be at center height. brownnsharp |
In article .com, brownnsharp
says... Using the new bore dimensions, make a new quill. Make the quill with steps in this order. First bore a through hole in a piece of steel which is the root diameter of the thread at the back of the quill. Thread the hole to match the screw. Another approach is to leave the threading to the last, and then bore the backside to accept a cylindrical bronze nut that is pinnned in place. This makes the ram threads easily replacable, and it separates the fabrication job into smaller bites. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
In article , Glenn Lyford says...
Inches ===== Measurement plane ===== in from Horiz. Vert., Vert., end unclamped 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. ...I would expect boring would give me a more accurate hole should the wear not be even front-to-back or top-to-bottom, whereas the reamer would follow the hole as worn, yes? Yes it would I think. If you just stuffed a reamer in there, the tailstock would probably droop by quite a lot afterwards. So boring it is a good way to go. Do you know anyone with a milling machine with a long enough travel, to simply set it up and do it in one shot? In this case of course you would want to indicate to the ways on the underside of the tailstock, or to the bottom part of the upper casting, if it's a split casting. The latter would be a bit better if the tailstock way surface were worn. Jim -- ================================================== please reply to: JRR(zero) at pkmfgvm4 (dot) vnet (dot) ibm (dot) com ================================================== |
jim rozen wrote:
Another approach is to leave the threading to the last, and then bore the backside to accept a cylindrical bronze nut that is pinnned in place. This makes the ram threads easily replacable, and it separates the fabrication job into smaller bites. That is a very good suggestion. My Smithy tailstock was made that way with a threaded cast iron bushing locked into the end of the ram. When the threaded bushing wore out I made a new one from bronze. Details may be seen at http://www.metalworking.com/dropbox/_2001_retired_files/TAILSTOK.TXT and associate drawing and photo. Although my problem was different than the OP's, the conversion would make the job easier. Also, if the OP has a boring head, it could be mounted in the lathe chuck. The tailstock could be positioned such that it could be moved with the longitudinal feed and the tailstock could be bored on the lathe. This should make for excellent alignment. Ted |
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