Revisiting OOR - Lathe alignment issue

[gomeral]

Well, I've finally bought some decent centers and tried to align them, and this is what I see:

So, side-to-side alignment appears pretty much spot on, but the top-to-bottom alignment is off. Turns out that the tailstock is lower than the headstock.

Is there an easy way to approach this? I'm thinking something like extremely thin UHMW tape under the tailstock. Anyone have any ideas?

It's hard to believe that this is the sole source of OOR problems, I'm sure my mandrel(s) has(ve) contributed to the problem - but I've got some bushings now for between-center turning and I'd like to fix THIS problem before proceeding.



Thanks,

daniel

 

[NewLondon88]

I'm not sure what UHMWEIEIO tape is, but a small amount of mis-alignment gets
magnified by the time you get to the middle of the mandrel. That small amount can
give you a bit of trouble with OOR.

I've used teflon tape (not the plumbers thread tape) to change alignment on parts
before. I forget where I got it, most likely some electronics store or supply house.
I used it to make parts move more freely and to eliminate film scratching in roller
transport systems. It's thin, tough and slick. I can see putting that on the bottom of
the tailstock to not only bring it up a fraction of a mm, but to make the tailstock move
like the ways are greased.

I should keep some of that tape on hand anyway, so if I find it online, I'll come back
with a link.

Another thin to check for OOR is any flex in the mandrel. An overtightened mandrel nut
or tailstock will cause the mandrel to flex (trying to put an 8" mandrel in a 7.99" space)
and this will also give you OOR. That extra bit of room from the tightening has to
go SOMEwhere...

I had a headstock alignment problem when I first got my lathe and found that if I put
the mandrel up to the TAILSTOCK first, then held it while I moved the tailstock and
mandrel toward the headstock (essentially backing it in..) it helped with some of the
OOR I was getting. Eventually I shimmed the headstock and the problem went away.

 

[gomeral]

I'm not sure what UHMWEIEIO tape is, but a small amount of mis-alignment gets magnified by the time you get to the middle of the mandrel. That small amount can give you a bit of trouble with OOR.

Ultra High Molecular Weight (UHMW) polyethylene. It's not as fancy as the teflon tape you mentioned, but it's basically the same thing. I'm going to search for some tape and consider this option - it's been tough to move the tailstock at times, anyway, so it's a good idea all around. (Get it? Ha.)




Thanks,

daniel

 

[keithkarl2007]

boy i'm glad you showed that, i just checked mine and its the opposite to yours, off from the side, guess i'll just turn the headstock a little

 

[Rudy Vey]

Good it is the tail stock, you could shim it with brass shimming material, these are thin brass foils that come in different thicknesses.

 

[NewLondon88]

Ultra High Molecular Weight (UHMW) polyethylene. It's not as fancy as the teflon tape you mentioned, but it's basically the same thing. I'm going to search for some tape and consider this option - it's been tough to move the tailstock at times, anyway, so it's a good idea all around. (Get it? Ha.)

(groan...) :tongue:

If the tailstock is difficult to move, and the nose is pointing down, it seems
possible that something is stuck to the bottom of the tailstock, at the back
end. This would cause both things.. difficult to move because something
is binding, and pointing down because something is holding the back end up.

Might be worth a look.. check for dirt, debris, shavings etc..

 

[randyrls]

Actually the best thing to use is thin aluminum shimming material. Fortunately, this is sold in a convenient form most everywhere, but you must empty the "packing material" used to prevent the collapse of the shims before cutting the material into the appropriate sized shims. You can also use the leaf type feeler gauges.

The Slick tape is sold by many woodworking stores among:
http://www.woodcraft.com/family.aspx?familyid=902

It looks to be 1/32" thick, or .031" thirty-one thou

 

[TellicoTurning]

I don't know it's thickness or even where you might find it, but I have a roll of aluminum aircraft tape that I picked up from the airlines I worked for about 30 years ago... it's the same width as normal 2" packing tape and strong enough that I've seen it used to tape over small holes in the skin of aircraft. We had a guy tear a small gash in the side of a cargo plane with the mast of a forklift (it was forbidden to have forklifts around aircraft).. the gash was about 6" long x 1/2" wide and the mechanics put this tape over the gash and sent the aircraft on it's way. I saw the plane back in SF at least 3 times with the tape still on it before it got patched properly.

The tape would be strong enough to take the sliding of the tailstock on the ways if it were properly waxed.

 

[gomeral]

Well, I used my micrometer to measure the gap, and it appears to be about 0.016", about 1/64". That complicates things because it's going to be hard to find a stick-on tape that thin. But, to make things worse, looks like my headstock wobbles. I put a mandrel in by holding it to the tailstock and using the TS to push it into the HS, but it wobbled terribly! I tried moving the tool rest underneath at certain points, including the large end of the taper before the mandrel shaft, and I get the dreaded "tick-tick-tick-tick".

EDIT: In retrospect, this confuses me - with a dead center in the HS and live center in the TS and the lathe running, there is no wobble visible, the two are just misaligned. With either of 2 mandrels, both wobble considerably. I'll go back out and check with yet another mandrel and/or try turning something between centers (likely just a spindle, not a pen).

Check this out (click picture to open 8.3MB movie):

I won't bother posting the image/movie showing the headstock handwheel wobbling, that could be a setscrew issue.

Anyway, I've got the manual and I'm going to look into disassembling the head, cleaning, and seeing if I can get it assembled correctly. Any caveats on that? Do I need special tools to assemble it aligned? I'm still thinking of that Packard Woodworks alignment tool, maybe I should just get it.

Anyway, thanks in advance for any advice!


daniel

 

[DurocShark]

That is a really tiny difference in the centers. My lathe has a bit of slop in the tailstock that results in more difference than that and I haven't had any trouble keeping my mandrel turned pens round. Even sierras (and those are thin!)

That little wobble in your video could definitely be the problem. Exasperated by the misalignment.

Definitely keep us updated on what solves it for you!

 

[amosfella]

I need to raise my headstock about a few hundredths of an inch. Or mill my tailstock down a few hundredths. Jet's quality control has really seemed to tank in the 1220 series.
Mind you, I had to raise my record's headstock with a few layers of denim as well......

 

[Randy_]

Shims can be cut from Coke cans or beer cans depending upon your pleasure. The material is about 0.003" thick so you can make some pretty fine adjustments.

If you need thicker shims and don't want eight layers of Coke can. most all hobby shops and many craft stores sell brass shimstock in various thicknesses.

 

[hughbie]

my thinking is the same as Randy's. a couple of long strips from a soda (meaning beer) can and you could use some double sided tape to mount it.....

 

[amosfella]

double sided tape can be pretty thick.......

 

[gomeral]

I spent a little more time on this Sunday night and I'm more confused now than I was when I first posted this thread.

First, I cleaned out the headstock and tailstock and lightly sanded the mandrel tapers with 600 grit wetted with WD40. With the dead center in the HS, I get no visible wobble. With a mandrel taper in the HS, I get wobble. With a mandrel shaft in the taper, I get a LOT of wobble (I should say "same wobble, more visible because of the extension"). I haven't had a chance to try the "rotate-the-taper-90º-and-see-what-happens" thing, but that will happen as soon as I get some shop time. But I've reproduced the wobble several times with two different mandrel tapers, and cannot see it with the dead center.

It gets better! If I put the dead center in the HS and the live center in the TS, then align the points and turn the lathe on, I get no wobble at all, but the up/down misalignment remains while the lathe is on. If I swap the two, the live center in the HS wobbles around the dead center!

ARGH! :beat-up:




daniel

 

[Paul in OKC]

Sounds like it could be a bad bearing in the live center. I do not consider the alignment issues as big as others. If you centers are running true, a small amount of offset will not cause issues. Think of a drive shaft in a rear wheel drive car. Yes, they have u-joints, but the theory is the same (to me, anyway). I have a dead center that I had to remachine because it was not true. I hae also done the 'knock-it-out-and-turn-it' trick to true things up. A pain, but it can work. I also second the pop can for shims, if you choose to do that.