# Tailstock vertical alignment???



## cdhknives (Jan 26, 2015)

When I insert my Jacobs drill chuck into my tailstock and try to drill anything, the drill bit hits low.  It doesn't matter how the chuck in inserted, what type of bit (spotting, stub length, or standard drill bits, though longer bits are more obvious.  As soon as the tip of the bit makes contact it lifts.  I assume it is trying to self center somewhat in the spinning workpiece.  Measuring the resulting 'center hole' shows it to be a little off but not really bad.

Still, the bit movement is disconcerting.  Is there a way in my old Atlas to adjust out this issue?  I looked and didn't see how I could shim the tailstock...so I'm scratching my head here...

I have a project in the works where I'll need very concentric holes in small parts (no room for boring bars to true things up) and I'd like to get this fixed.


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## cathead (Jan 26, 2015)

Most tail stocks are made of 2 pieces so you can shim in between the base and the
top part.  If not, there is some filler stuff called Moglice but I have no Idea if it
would hold up and do the job.  Maybe someone on the site knows. 



cdhknives said:


> When I insert my Jacobs drill chuck into my tailstock and try to drill anything, the drill bit hits low.  It doesn't matter how the chuck in inserted, what type of bit (spotting, stub length, or standard drill bits, though longer bits are more obvious.  As soon as the tip of the bit makes contact it lifts.  I assume it is trying to self center somewhat in the spinning workpiece.  Measuring the resulting 'center hole' shows it to be a little off but not really bad.
> 
> Still, the bit movement is disconcerting.  Is there a way in my old Atlas to adjust out this issue?  I looked and didn't see how I could shim the tailstock...so I'm scratching my head here...
> 
> I have a project in the works where I'll need very concentric holes in small parts (no room for boring bars to true things up) and I'd like to get this fixed.


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## NightWing (Jan 26, 2015)

I would look at the drill chuck before I started shimming anything.  It could have worn jaws or the shank may have an error.  Is it a genuine Jacobs chuck or an imported knock-off?  Even Jacobs chucks are available in several degrees of accuracy.


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## SG51Buss (Jan 26, 2015)

First, need to determine if the tailstock ram is angled downward, or parallel but lower, or a combination of both.  Use the dead centers to determine this...


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## cdhknives (Jan 26, 2015)

NightWing said:


> I would look at the drill chuck before I started shimming anything.  It could have worn jaws or the shank may have an error.  Is it a genuine Jacobs chuck or an imported knock-off?  Even Jacobs chucks are available in several degrees of accuracy.



The drill chuck is probably 50 years old and is stamped Jacobs, so I assume it is genuine.  If it was worn, wouldn't the bits hit low/high/left/right as I rotate it in the tailstock?


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## davidh (Jan 26, 2015)

my tail stock shaft also lifts a little unless i sorta snug up on the lock, just enough to keep it from moving.  i too have a craftsman / atlas.


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## Dranreb (Jan 26, 2015)

Mine does the same, Atlas 10f, what I do is to face off the part (a sharp pointed tool is needed for this) then while the tool is still centered, I advance the tool into the center of the work to make a small depression. This works like a punch mark and stops the drill wandering off.

Bernard


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## benmychree (Feb 3, 2015)

I had an American Tool Works 14" lathe from WW-1 era that had a tailstock that rocked on the ways, was below center, and the quill sloppy and the keys between the top and bottom parts sloppy;  I re machined the Vees, replaced the keys with oversize and remachined their seats, then line bored it in place with a long boring bar supported in a bushing in  the steady rest ( tailstock between the chuck and steady rest) I hung a heavy weight under the tailstock to hold it to the ways and pushed it into the cut with the carriage, then made a new quill.  This made a "new" machine of it!  In most cases, a shimming between the two parts of the tailstock is sufficient to overcome the problem that you describe.  Another cause can be having drill repeatedly spin and gall up the taper in the quill.  I do all my drilling with the Aloris drill holder using carriage feed; best to only use the tailstock for it's intended purpose, that is holding the lathe center.  I have, however seen the American Pacemaker lathes that have a tang slot in the tailstock quill; this will greatly lessen the tendency to scrrew up the taper, but bear in mind that tangs can be twisted off ---


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## cdhknives (Feb 5, 2015)

I broke out the indicator and some dead centers and went to town.

Dead centers in both head and tailstock meet point to point...visually perfect...both with tailstock fully retracted and fully extended.

Indicator run down the extended ram shows no visible deflection the entire length.  I repeated this at 3 positions on the bed with identical results.

Some flex with moderate pressure is present but I would guess inevitable on this size machine.

Maybe it is the chuck, or maybe I need to sharpen my drills (especially my spotting drills).


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## dirty tools (Feb 5, 2015)

You should first check the alignment between the chuck and the tailshaft.


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## wa5cab (Feb 6, 2015)

One other check that you could make is to mount a piece of 1/2" round with about an inch sticking out of the chuck.  Turn the compound around to -30 deg. and sharpen the piece.  Check again with a dead center in the tailstock.

Robert D.


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## SG51Buss (Feb 13, 2015)

Old thread, but been thinkin' on it for awhile.

Suppose that the tailstock chuck were worn enough that loose jaws and a long/heavy drill bit would settle aimed downward, from gravity.

One way to test this would be to apply upward pressure on the drill bit tip while tightening the chuck.  Then, see if its center has changed...


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## cdhknives (Feb 18, 2015)

No movement under moderate pressure and a heavy drill bit installed.


I had a medical induced stand down (stitches in the hand, see safety forum) , so I've spent the last 2 days looking at this lathe.  Using my best dead centers and taking my time, the tailstock center point is about 1/16" lower than the spindle center.  I'm assuming wear to the bottom of the tailstock, so now I look at shims.

Do you try to shim between the tailstock and the lathe bed (how do you keep them in place, mini pins?) or between the halves of the tailstock where it slides for adjustment (looks like the retainer fingers would be a problem)...???


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## wa5cab (Feb 19, 2015)

I think that you already confirmed that the ram was parallel to the bed (no droop).  The shims should go between the tailstock casting and the base.  So two pieces to clear the key and keyway.  Bed wear due to tailstock movement is probably negligible.  It doesn't run on the same part of the ways that the carriage does.


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## cdhknives (Feb 21, 2015)

I had some 1" wide brass strips that came with the lathe.  The thinnest was .0165" and placing a strip between the halves of the tailstock put the dead centers point to point...visually as close as I can get.  I used 2 strips, one under the front and one under the back right at the front and rear edges.  There is now a gap between the halves, but I don't think that will be a problem.  

There was not a great deal of wear to the bed contact surface...the original machining marks are mostly still visible.


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## fgduncan (Mar 5, 2015)

Now when you think that you have the problem solved, turn a test bar between centers.  That is when you will find out whether you still have a problem or not.


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## challenger (Mar 14, 2015)

The best way to check the ts quill and bore is to turn a piece of stock to the exact diameter of the ts quill. Run a di along the side of the part then on the side of the ts quill. Do the same for the top side of both. This will give all the alignment and accuracy tests for the ts. Much easier than turning two collars. 
This method was shown to me by a machinery rebuild of the highest regard.


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## cdhknives (Mar 14, 2015)

But how do you differentiate between misalignment from elevation and misalignment from horizontal offset?  Both would show up as a diameter change between head and tail ends...and both could be larger or smaller (or offset each other).  Without a properly aligned tailstock, I simply can't turn a piece and get uniform diameter the entire length!


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## wa5cab (Mar 15, 2015)

Except on very small diameter parts, diameter error caused by tailstock height error is about two orders of magnitude less important that back-set error.


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## wa5cab (Mar 15, 2015)

CDHKnives, I think that he means to turn a piece in the headstock chuck without it's being supported by and affected by the tailstock.  If you have an extra ram, you can use that but you will need to use a 4-jaw chuck so that you can zero out the runout.  With that setup, you would merely zero the dial indicator on the piece in the headstock and then run the carriage over and check the tailstock ram both fully extended and nearly retracted.  And adjust as required.  However, keep in mind that all methods will potentially be affected by bed wear.  As I wrote last night, vertical error is less important than horizontal.  See the .TXT file attached.  When Downloads works again, it will be in there.


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## John Hasler (Mar 15, 2015)

cdhknives said:


> I had some 1" wide brass strips that came with the lathe.  The thinnest was .0165" and placing a strip between the halves of the tailstock put the dead centers point to point...visually as close as I can get.  I used 2 strips, one under the front and one under the back right at the front and rear edges.  There is now a gap between the halves, but I don't think that will be a problem.
> 
> There was not a great deal of wear to the bed contact surface...the original machining marks are mostly still visible.


Sandwiching a steel rule between the points of the centers will give you a very sensitive indication of alignment.  Do this with the ram both extended and retracted.


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