Tailstock vertical alignment???

cdhknives

cdhknives

Active User
H-M Supporter Gold Member
Joined
Apr 12, 2013
Messages
562
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.
 
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.
Click to expand...
 
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.
 
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...
 
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.
Click to expand...

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?
 
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.
 
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
 
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 ---
 
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).
 
You should first check the alignment between the chuck and the tailshaft.
 
You must log in or register to reply here.
Back
Top