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Drawbars?

Tom Albrecht

Tom Albrecht

Joined
Feb 8, 2014
Messages
1,219
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659
Location
Evanston, IL USA
I sometimes use Morse Taper collet chucks that are held in place with a 3/8" draw bar.

I have noticed that some of the newer Morse Taper drives and live centers are threaded for 3/8" drawbar use. When, and why, would one use a drawbar to pull in a drive or a live center?
 
Tom Albrecht said:
I sometimes use Morse Taper collet chucks that are held in place with a 3/8" draw bar.

I have noticed that some of the newer Morse Taper drives and live centers are threaded for 3/8" drawbar use. When, and why, would one use a drawbar to pull in a drive or a live center?
Click to expand...

I would say use the drawbar anytime the chuck is not otherwise constrained from backing out of the spindle. I set my drawbar up to length so that it takes only a few turns of the bar and wingnut to safety the collet chuck.
 
You can't use a draw bar in many tailstocks because they change length when you crank out the quill. I'm not sure why you would use a drawbar on a drive center in the headstock. The stock pushing against the morse taper would lock it in place. As Al said a drawbar can be an essential item in a drill chuck with a morse taper. They are notorious for coming loose especially if you use them for things other than drilling, like buffing, or with a wire brush installed.
 
The simple answer is that it keeps it from slipping. Always use a draw bar if you can. Once a MT slips, it will often damage the MT and the spindle. If this happens too much, you'll have to get a reamer to fix the internal surfaces of the spindle.
 
Many thanks for the videos, Alan! They were first quality and the narrative was easy to follow and understand along with the demo on the lathe.
I learned something today! Old dog, new tricks, you might say. I'm going to the shop and see if my MT2 items are threaded.
 
Thanks for the kind words about the videos. I have plans for a few more, so stay tuned.
 
John Torchick said:
Many thanks for the videos, Alan! They were first quality and the narrative was easy to follow and understand along with the demo on the lathe.
I learned something today! Old dog, new tricks, you might say. I'm going to the shop and see if my MT2 items are threaded.
Click to expand...


Alan. my thoughts as well. Thanks, Gretch
 
Oh no! Nothing with an MT2 taper is threaded. Now I'll have to buy all new stuff. ;) Don't tell SWMBO.
 
John Torchick said:
Many thanks for the videos, Alan! They were first quality and the narrative was easy to follow and understand along with the demo on the lathe.
I learned something today! Old dog, new tricks, you might say. I'm going to the shop and see if my MT2 items are threaded.
Click to expand...

Add me to the list of admirers! :D

Be sure to post the new videos here on main forum......thanks!

ko
 
Pete Blair said:
Something I always wondered about is if dragging a threaded rod through the headstock will damage the inside? I would guess that it is hardened but am unsure. I have seen some who put a small rubber washer on the bar. Is this necessary? Anyone?
Click to expand...

Pete.......My first thought is there would be no problems, but an O-ring at intervals would keep your mind at ease about this. I would think the act of sliding a threaded rod through the interior of the hollow wouldn't be a problem at all......there is virtually no pressure of the threads against the spindle hollow.....it's nothing more than a "slide". Any thought of the Morse Taper at risk should be dismissed, since you won't be inserting the rod without a Morse Taper attachment already inserted from the other end......

ko
 
Pete Blair said:
Something I always wondered about is if dragging a threaded rod through the headstock will damage the inside? I would guess that it is hardened but am unsure. I have seen some who put a small rubber washer on the bar. Is this necessary? Anyone?
Click to expand...

I agree with Odie's comments that the spindle has been hardened and the all-thread is probably softer material. However, these days you never know for certain what is in hardware store all-thread since it is recycled steel of the lowest quality which means that it Is likely to have hard chunks of carbides amongst other unknown mixtures of different alloys. Just to be safe, you could clean up the all-thread by running it through a die a couple times. You will probably notice that the threads are not exactly smooth so one other thing that can be done is to smooth the thread peaks with 1500 grit silicon carbide paper or fine crocus cloth. The coup de grâce could be to wrap Teflon tape around the all-thread.
 
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Can't even tell you how many times I've run a piece of all thread or Draw bar through my various lathes. No problems whatsoever.
 
Dennis J Gooding said:
If the drawbar is reasonably straight, it cannot contact the morse taper portion of the bore and so poses no threat.
Click to expand...

May i remind you of some of the corollaries to Murphy's Law:
  • It is impossible to make anything foolproof because fools are so ingenious.
  • Nothing is foolproof to a sufficiently capable fool.
  • Make something idiot-proof, and they will build a better idiot.
 
Good observations, Bill. Also: Compared to me, Murphy was an optimist. Wrap the all-thread with duct tape.
 
When I've had occasion to use a draw bar in a situation like a wood lathe I put a plastic or wood sleeve around the draw bar. The sleeve fits close enough to the spindle bore to align the draw bar with the threaded hole in the Morse taper.

Draw bar to Morse taper thread alignment is especially difficult on a metal lathe with a spindle reducer sleeve to go down from a #4 to a #2 Morse.
 
... Or if you really want to be neat about it, put some heat shrink tubing over the threads.

I don't think it's at all necessary, but it's an excuse to play with the tubing and a heat gun.
 
AlanZ said:
... Or if you really want to be neat about it, put some heat shrink tubing over the threads.

I don't think it's at all necessary, but it's an excuse to play with the tubing and a heat gun.
Click to expand...

More toys ... er, uh ... tools are always a good thing. I've always wanted a heat gun ... using matches or a charcoal lighter is always dicey ... sometimes I melt the HS tubing and sometimes I set it on fire ... occasionally I get it almost right.
 
Funny that references to Murphy's Law and to Heat Gun should pop up in the same thread. I bought a heat gun about 20 years ago or so. On the first time out, I managed to fry the power cord of the gun through inattention and have leaved with an ugly patched cord since.
 
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