Pneumatic drawbar question

[dado5]

I have been watching build videos on pneumatic draw bars and am thinking about uilding one. Since I am new to this I can't help but wonder why nobody seems to worry about crossthreading the bolt into the tool/collet with the pneumatic gun.

 

[Ed ke6bnl]

wondering the same thing. and what makes it so you don't have to tap the draw bar at the top to release.

 

[spumco]

(I'm assuming you're talking about the pneumatic butterfly wrench arrangement, and not a CNC-type air cylinder with spring washers)

The drawbar isn't fully withdrawn from the collet when it's loosened. Just enough to permit the taper to spring loose and slide the tool out.

If you change collets then you'll need to hand-thread the drawbar in to the collet and push the collet/tool up in to the taper and then drive it home with the pneumatic wrench/gun/whatever. If you don't do this, then your speculation about cross-threading would be valid - as well as wrecking the spindle if the key isn't lined up.

I don't have one, but I understand that the impact/rattle action of the gun helps loosen the collet from the spindle taper and you generally don't have to give it a whack to loosen the collet.

 

[coffmajt]

I just built one for my milling machine and have not had any concerns or problems with the drawbar threads to the tooling. So far only once has the tool been so tight in the R8 taper that I needed a slight tap on the drawbar to loosen the boring head I was using. I really like the ease of use == Jack

 

[kd4gij]

On a BP type mill if you push the collet all the way up in the spindle the draw bar will be lined up and start no problem. I have used a PB with a Kurt power draw bar for 10 years at my last job and never had an issue. With the Kurt you can't get to the draw bar with it installed.

 

[Frank Ford]

With a Kurt (maybe others, too) you can't reach the drawbar, so instead of tapping the drawbar to loosen a stuck collet taper, you can run the drawbar partly or all the way out, and raise the quill with a quick jerk to drop the collet or tool right out.

 

[Jake2465]

Are these the kind of draw bars where you put a tool holder in the quill, press a button and it makes a noise like removing a lug from a car tire?

 

[kd4gij]

Are these the kind of draw bars where you put a tool holder in the quill, press a button and it makes a noise like removing a lug from a car tire?

That be it.