Draw Bar Tightening Torque

[Tozguy]

I just picked up an MT3 tool holder for holding 1/2'' Sheldon shanks. The end of the MT3 taper is threaded 3/8-NC. My draw bar runs through the lathe spindle and is around 14'' long with a hand knob for tightening. I would like to know how tight these draw bars need to be.
Of course the taper surfaces will be clean and dry as usual so I am not expecting to have to torque the knob a whole lot. Or does it vary depending on the job to be done?

 

[Bill Gruby]

If the Tapers are clean they hold the holder. The Draw bar keeps the MT3 Taper in place, ie. it can't fall out. Just past hand tight will do the trick. It need not be forced.

"Billy G"

 

[janvanruth]

insert the taper into the spindle and give it a tap with a rawhide/lead/copper hammer
then handtighten the drawbar

 

[Tozguy]

Thanks.

 

[dlane]

How bout on a BP clone mill , r8 tooling , often wondered how tight is to tight for the drawbar

 

[T Bredehoft]

R8 tooling, I feel it depends on the tooling, collets, I try to give a little more torque than tool holders. There's a set screw holding the cutter in a tool holder, but when the cutter is held by the collett it needs more tightness than the tool holder. I can't give you torque values, it's something you develop.

I don't know about too tight, but too loose is when you loosen the drawbar and the cutter falls out of the collet without you rapping on the drawbar.

 

[Johnnybar]

Getting MT tool holders out is a lot less headache than a galled spindle taper...so tighten well and who cares if it takes a few whacks to remove.

 

[4GSR]

....snip.........so tighten well and who cares if it takes a few whacks to remove.

That's too tight!

 

[Wreck™Wreck]

If the Tapers are clean they hold the holder. The Draw bar keeps the MT3 Taper in place, ie. it can't fall out. Just past hand tight will do the trick. It need not be forced.

"Billy G"

Where I work we have a large radial drill press with an MT 8 taper spindle, the taper is so clapped out that the tools often fall out before one can get the part under them, a drawbar would be a nice touch.
The OP will find that if the spindle is in decent shape MT tools will be more difficult to remove then install after great force is applied. Draw bar torque needs to be light with such a taper.

 

[Johnnybar]

That's too tight!

I find that a tightened drawbar locks the holder in place no more than a mallet whack and is easier on the bearings. Maybe our definitions of "whack" and "tighten well" differ considerably in addition to highly probable variances in the spindle and tooling's lockup tendancies.