Best Material for Tailstock Spindle?

tobnpr · Oct 24, 2020

I've decided to replace the tailstock spindle on my Sheldon lathe.
Lathe was in excellent shape when I acquired it, but the tailstock taper was badly boogered up so I cleaned it up with an MT reamer. Unfortunately, the extra depth required to clean it up completely forced me to face about 3/8" off so the tooling would seat correctly. Plus, it was shorter than it could have been from the factory- fully retracted I've got nearly a full inch of the spindle inside the barrel. So, I want to get back to factory length, and then some.

The spindle is precisely 1.250
Is drill rod a good choice for this? If so, what grade would be best as compromise between hardness, and machinability? If not drill rod, what should be used?

The factory spindle has a threaded insert in the back of the spindle, so I will only need to drill/bore the replacement to swap it over (no internal threading needed).

Thanks in advance for the advice.

john.k · Oct 24, 2020

I made a missing spindle for a Colchester Bantam from 4140HT,and it worked OK for a long time ......you will likely find the casting bore a bit worn,and its usual to hone the bore parallel,then grind the barrel to suit........although it could be turned in a accurate lathe,grinding will make for a much better fit....It should be so tight it can just barely be pushed in by hand ,or maybe even a little tighter ,to allow for initial wear.(the clamped split type have a bit more latitude for fit)

Phil in Montana · Oct 24, 2020

Make your live easy use 1140 stress proof, easy to machine, but if you want a real good one us ph 4140.. that will make a machinist out of you...Phil

john.k · Oct 24, 2020

One thing I miss from the original is the graduations ,but I suppose I could have done them .The 4140 HT is probably not hard enough on the OD,but mine has never scored or marked,.The original setup had a cross drilled hole with the screw thread in the cross drilled insert,hard to visualize until seen......anyway ,I was missing this also,so I just installed a bronze insert in the barrel,and threaded that with the 10tpi LH Acme of the screw.Works 100%,but not used that often ,because the Bantam is seldom used for anything but very short work ,being only 19" BC,and I have larger machines.

gregoryd · Oct 24, 2020

What about TGP 1045? Its not the same as a 4000 series, but the tolerance and finish that you get from the start is compelling.

rklopp · Oct 24, 2020

I made a tail stock ram for my Monarch 10EE out of ETD-150 “Fatigue-Proof.” I had the body bore honed and then turned and lapped the ram to fit. I tried to bore the MT2 taper from first principles using a sine bar, but that bombed and I ended up reaming with an MT-2 reamer to finish it up. McMaster sells ETD-150.

I put the graduations on in the CNC mill using a slitting saw with a V profile on the teeth. There’s no numbers, but who’s counting. [emoji2957]

Sent from my iPhone using Tapatalk

gbent · Oct 24, 2020

Consider repairing the spindle with a MT adapter with a straight OD. Bore your existing spindle for a line on line fit, and secure the MT adapter with locktite using the primer. If you apply a press fit, part of the press fit will expand the od of the spindle. If this is desirable, go for it, but it could make the spindle to snug in the bore.

jims · Oct 24, 2020

Fix tailstock

tobnpr said:
I've decided to replace the tailstock spindle on my Sheldon lathe.
Lathe was in excellent shape when I acquired it, but the tailstock taper was badly boogered up so I cleaned it up with an MT reamer. Unfortunately, the extra depth required to clean it up completely forced me to face about 3/8" off so the tooling would seat correctly. Plus, it was shorter than it could have been from the factory- fully retracted I've got nearly a full inch of the spindle inside the barrel. So, I want to get back to factory length, and then soIIme.

The spindle is precisely 1.250
Is drill rod a good choice for this? If so, what grade would be best as compromise between hardness, and machinability? If not drill rod, what should be used?

The factory spindle has a threaded insert in the back of the spindle, so I will only need to drill/bore the replacement to swap it over (no internal threading needed).

Thanks in advance for the advice.

I think if I had to fix the tailstock I would drill out the old tailstock spindle and bore it to fit a strait shank drill socket with the Morse taper already in it. Then I would weld it in.
Jim Sehr

tobnpr · Oct 25, 2020

jims said:
I think if I had to fix the tailstock I would drill out the old tailstock spindle and bore it to fit a strait shank drill socket with the Morse taper already in it. Then I would weld it in.
Jim Sehr

I think I like this idea, I hadn't seen these straight shank socket adapters before:
TTC 2 MT Hole Solid Socket With Morse Taper Hole Solid Socket | 67-004-004 | Travers Tool Co., Inc.

Boring out the existing spindle will leave me 1/8" wall thickness (adapter OD 1", spindle 1.25") which I think should be sufficient? To maximize spindle travel, I'd leave 1" of the adapter protruding beyond the end of the existing spindle. Again, I don't think this would be an issue, the spindle clamp is still behind where the junction would be. There's little to no wear in this assembly- I gotta believe that the 1.250 was the original diameter, and the barrel mikes out at 1.252. I don't know what factory dimension was, but there's only .001 clearance around the spindle now.

I was thinking sleeve retainer would be sufficient, but I would have that 1/8" "lip" around the front that I could tack in a few places to make sure it can't spin out.

I have rough/finish MT2 reamers, but this seems the easier way to go.

Phil in Montana · Oct 25, 2020

After seeing some of the bad ideas, you have to decide if you want to cobble the lathe up or make it right, this will have everything to deal with you being a machinist or not. Any backyard dude can cobble it, but it takes a machinist to do it right and have a good lathe when you are done, and the right way is Never the easy one...Phil

dian · Oct 25, 2020

consider using moglice or similar. boring the tail is not trivial and you could get a perfect alignment that way.

tobnpr · Oct 25, 2020

Phil in Montana said:
After seeing some of the bad ideas, you have to decide if you want to cobble the lathe up or make it right, this will have everything to deal with you being a machinist or not. Any backyard dude can cobble it, but it takes a machinist to do it right and have a good lathe when you are done, and the right way is Never the easy one...Phil

I don't mind a "shortcut" if, at the end of the day, the end result is the same- indicators don't lie, right?

How can boring the spindle result in anything other than it being perfectly concentric to the spindle axis provided the setup is correct. I can dial in rifle barrel bores to within two-tenths with a long-stem Interapid. I fail to see how using the same diligence in setup with the tailstock spindle will result in something that's been "cobbled" together with inferior results? Not trying to argumentative- just let me know what I'm missing here?

dian · Oct 25, 2020

how long is the spindle? have you practiced on a bore that long? you say spindle is "exactly 1.250". is it 1.2500? what are you going to bore to for a medium sliding fit? are you going to hold that on the entire lenght? your numbers are a bit suspect. with one thou clearance the spindle would be rattling in the bore.

Erich · Oct 25, 2020

Guarantee you that the lathe did not leave the factory with .002 inch clearance. more like .0005 . The tailstock bore is probably worn bell mouthed to boot. Fixing that requires the machinist chops Phil was talking about.

tobnpr · Oct 25, 2020

Cleaned everything up and took some more precise measurements. The 1.250 was not correct.
The spindle is just under 5-1/2" currently, don't know why it wasn't made to maximize travel, but fully retracted it's inside the barrel by nearly an inch.

At the nut end, the spindle is 1.2455
Mid-length= 1.2492
Outside end= 1.2492
Diff: .0037

Barrel:
Did not disassemble screw, with telescoping gauge ID = 1.2512 as far in as it would go...
At the outside end, 1.2526
Diff .0014

With 2" of spindle extended/unlocked, I can get about .003 play side-to-side pushing as hard as I can.
With the spindle locked, only .0002 movement.

I work with 4140 more than anything else so I'm used to it.
Ideally, if 1.250 would work I'd try to find "stock" round bar that diameter PH and ground- so I'd only need to drill/bore/ream and cut the keyway.

But ya'll are saying that .0012/ .0006 per side is too much clearance for a tailstock spindle?

dian · Oct 25, 2020

if you have play in the spindle it will change location depending on stickout when clamped. theat means the center will really be centered in one position only.

boslab · Oct 25, 2020

Hydraulic rod works, done that once (dsg 17”)
Mark

4GSR · Oct 25, 2020

From the two Sheldon lathes I've owned, I highly doubt Sheldon used anything more than 12L14 or 1215 for tailstock spindle. Maybe 1045 if they ran out of a particular grade of material. Since you have access to 4140PH, go with that for a new barrel.

Way back many years ago, I rebuilt a lathe that had a tailstock barrel that probably had .030-.045" slop in the housing. Once I got the tailstock base remachined and scraped to the bed, I set up a make shift boring bar in the headstock spindle and proceeded to line bore the tailstock housing out. Once done, I was lucky and got ahold of a old decent looking barrel that was oversized. Machined the OD to a "zero" fit. Did this in the lathe since I didn't have access to a cylindrical grinder. Lots of polishing and made it a very snug fit. The OD of the spindle was around 3". It was tight enough you couldn't move it by hand. That spindle was some kind of alloy heat treated to the upper 30's if not lower 40's in Rockwell C hardness.

Just though I would share this, Ken

jims · Oct 25, 2020

Tailstock spindle

4GSR said:
From the two Sheldon lathes I've owned, I highly doubt Sheldon used anything more than 12L14 or 1215 for tailstock spindle. Maybe 1045 if they ran out of a particular grade of material. Since you have access to 4140PH, go with that for a new barrel.

Way back many years ago, I rebuilt a lathe that had a tailstock barrel that probably had .030-.045" slop in the housing. Once I got the tailstock base remachined and scraped to the bed, I set up a make shift boring bar in the headstock spindle and proceeded to line bore the tailstock housing out. Once done, I was lucky and got ahold of a old decent looking barrel that was oversized. Machined the OD to a "zero" fit. Did this in the lathe since I didn't have access to a cylindrical grinder. Lots of polishing and made it a very snug fit. The OD of the spindle was around 3". It was tight enough you couldn't move it by hand. That spindle was some kind of alloy heat treated to the upper 30's if not lower 40's in Rockwell C hardness.

Just though I would share this, Ken

I would look at MSC Tools Part # 03732393 Morse taper rough socket. You would have the inside taper done and only have to grind or polish the od. I don’t know but to me boring a one off Id taper is a pain. But I have only been machining a little over 60 years so what do I know. And you get the material in the deal.
Jim Sehr

richard newman · Oct 25, 2020

4GSR said:
I set up a make shift boring bar in the headstock spindle and proceeded to line bore the tailstock housing out.Ken

Wondering how you set this up? I'm thinking I would put the tailstock between the headstock and the carriage, and use the carriage feed to advance tailstock on it's ways. The boring bar would be held in the chuck and a steady rest at the end.

Best Material for Tailstock Spindle?

Hot Rolled

Diamond

Stainless

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Hot Rolled

Diamond

Diamond

Hot Rolled

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Stainless

Titanium

Hot Rolled

Titanium

Hot Rolled

Hot Rolled

Titanium

Titanium

Diamond

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