Bridgeport power drawbar question

[dr_clyde]

Apparently this isn't a problem, but I haven't figured out how it's not. I'm starting to think about adding a power drawbar to my mill. R8 spindle and I mostly use er25 collets. But when I need a face mill or want to use a drill chuck, I do have to pull the r8 collet out. So the power drawbar will make that a little easier.

Here's my question... When I loosen the drawbar now, I have to tap it to loosen the collet from the taper. Using an impact to loosen the drawbar, there's not enough room to do that and the videos I've seen make it apparent that it's not needed anyway. Why doesn't the collet stick in the taper?

To answer your question, a power draw bar pushes down on the drawbar with some amount of force. This in conjunction with the threads being loosened on the collet are sufficient to knock the collet loose.

The R8 is not considered to be a locking taper, but they do get sticky. They do require a rap from the side of a wrench or a hammer if you are loosening the drawbar manually, but the force is minimal compared to a Morse or Jacobs taper. The force from the power draw bar pushing down is plenty.

 

[lilscorpion]

For single ops there’s really no need for a power drawbar but on multiple op with multiple tools it’s almost a necessity especially if you have CNC and absolutely if you’re making more than a few parts. I’ve had setups where I’ve switched between maybe half a dozen tools (spot drill, couple of drill steps, end mill slots, chamfer, etc).

They’re relatively cheap compared to other upgrades to a mill and they last forever if you have an auto oiler.

 

[Hephaestus29]

I made my own Power Draw Bar, you can find it on here somewhere. It's made from a couple different things. A horrible freight butterfly air wrench, and a Bosch Plunge Router base. Of course I did other things as well but, it works great.