jacobs chuck not holding in tailstock?

[tmenyc]

what am I missing here? My Jacobs chuck, a 36, mounted to a Jacobs arbor with 2 Morse tapered Jaobs arbor, won't hold tight in the tailstock. It advances and retracts ok, but there isn't a tight fit and when the lathe is at speed it turns with it. I have not done anything with restoring the tailstock, just oiled it. It seems to hold a center fine.
What do I need to know, what am I missing?

 

[ddickey]

The MT2 is new? Do other tools with an MT2 hold okay?

 

[RJSakowski]

Do you have oil on the taper ir socket interior? The taper and socket should be dry. If there is oil inside the socket, it can be removed by wiping with a clean rag until there is no evidence of oil remaining and then wiping with an acetone dampened rag and allowed to dry.
How about debris or burrs on the taper or in the socket? Check the socket by bluing the taper with a magic marker and inserting in the socket seat gently and rotate the chuck. Remove the chuck and examine the taper. Idea;;y, you should see uniform rub marks. If there are bright lines on the taper, There is probably a burr in the socket. This can occur when a taper spins in the socket under load.
Finally, how well did you seat the taper in the socket? For heavy drilling, I will tap the chuck with a dead blow hammer or place a piece of wood on the chuck face and tap with a hammer. You can seat the chuck by advancing it into a block of wood backed up by the headstock chuck with the tailstock feed.

 

[tmenyc]

DD no none of it is new. Except for my PM carbide bit set and the wiring, everything came with the lathe. I’m buying as needed.
RJ, thanks, I’ll check it out.
Tim

 

[Larry Hoy]

Try this a major cause of a taper slipping, is a bit will hog in and pull out of the socket. Try putting a tool bit in and put it against the chuck and push the carriage as you advance your bit into the work. I sometimes will snug the carriage lock a bit The sharper a bit is the more it will hog in. I read this tip in a 110 year old magazine and it works for me.

 

[mikey]

Tim, a morse taper is an interference fit. Either it fits or it doesn't. If it fits, it will hold. If it doesn't fit then the arbor or the tailstock may not be the right taper or there is a defect in one or the other.

On older lathes that have seen use by a less than careful worker, the tailstock taper will be buggered up by having had an arbor spin in there under load. This can really mess up the taper. They make reamers to fix this very problem. Do as RJ says and blue a known GOOD MT2 arbor and check the taper. If it is off in more than a tiny spot, ream it to fix it.

 

[tmenyc]

Mike,
thanks; the lathe was owned by an aeronautics instructor at NYC's aero high school. I suspect it was his pride and joy, and wasn't used by the students. So I'm hopeful that I'll find some grit in there but that it won't need reaming. I'll definitely follow RJ's advice. Maybe tomorrow.

Tim

 

[mmcmdl]

Make sure that you check the tang on the arbor for interference in your tailstock slot . On many occasions I've had arbors not seat for this reason , and had to thin the thickness of the tang . If it's good , check the taper by blueing it up as stated above . If it's out by 10 miles , ream it with the correct MT reamer . If it's only out 1 mile , lap it in . Make yourself ( or buy ) a MT lap , charge it up and clean your taper up .

It does sound to me like you have a tang interference problem though .

 

[Janderso]

The Chineseum Morse Taper reamers are very inexpensive, if you get one that was ground correctly that is.

 

[tmenyc]

I finally had a chance to disassemble the tailstock, which had not yet happened on my watch. First, the inside of the tailstock spindle was neither clean nor dry, so that will be easily fixed. It does not appear to be anything but dirty, but I'll know more after its WD40 soak. First it get WD40, then dried by rag, then Castrol Super Clean to wash out the WD40 remains, then air from my compressor to get it squeaky clean and dry?

Then I'll do a good test of the Jacobs chuck and my 3-4 Morse tapers.

Update:
The spindle cleaned up beautifully. Using long q-tips on wooden handles, I got all of the grunge from the spindle's furthest end and the rest is clean! I wiped it clean with a clean rag, poured some Super Clean through it, blew air after that, and it's clean and dry. Worked wonderfully.

Rubber Washer?
Second, a question: the rubber washer (LA-793) that sits on the tailstock screw is MIA, not AWOL from my work but simply absent. Is that a standard rubber washer, as in whatever fits? Or, do I need to get one from Logan Actuator?

Many thanks,
Tim