What is the proper way to remove a toolholder from a milling machine?

[HMF]

Hey Guys,

On a Bridgeport-type mill, is it "proper" to remove the collet by loosening the drawbar slightly and then giving the drawbar a good wallop to release the taper, or will that cause damage to the spindle?

If not, what is the "proper way" for doing it?

In the Darrell Holland video on mills, he locks the quill, holds the drive lock, loosens the draw bar and just gives the drawbar nut a good wack.

is there a way around hitting it, like using a drawbar that is captive with a left-hand nut so that, as you loosen the drawbar, it comes up against the nut and can't go any further, forcing the collet down?

Opinions please?

Thanks,


Nelson

 

[rleete]

I work in a place that has a precision production shop. Our Bridgeports are all 45-60 years old, and that's the way it's done around here. All these machines have held up just fine with no problems.

Note that you do NOT need to really tighten the drawbar nut, just snug it up. So, a tap is all that's needed, not a really good whack. The nut idea sounds like overkill.

 

[8ntsane]

Hi Nelson

I dont know if its eched in stone, but to loosin the draw bar a few threads and give it a tap to release the collet is pretty normal. If your talking about a mill that has a M/T, well thats a different story. M/T collets take a fairly swift wack to get them to release.

If the mill in question is a R-8 equipped machine, it shouldnt take any more than a tap. Before I made the power draw bar on my mill, I would just loosin the bolt, and tap the draw bar with the same wrench, no hammer needed.

A buddy of mine rigged up a simple fixture that is just a bolt on to his wells index mill. Its just a U shaped deal, that bolts on where the power draw bar would. It is like a bridge above the draw bar. It has a hole in the centre for the draw bar hex to go through the middle. the draw bar has a washer welded to the hex, and he just loosins the draw bar till the washer bears up on the bottom of the bridge. This pushs the draw bar down as it touches, and the collet pops loose. The only thing I didnt like was you had the spin the collet out by hand, so if the spindle has that alignment pin still in there, it has to be removed.

He is one of those guys that just wont wack the draw bar in fear of doing bearing damage. His simple rig isnt perfect, but I must admit, Ive never seen him hit the draw bar to release a collet.

On a final note, you could make up a simular deal, that would allow you to lower the quill a inch or so, loosin the draw bar, and raise the quill to knock the collet loose. Of coarse this would require a longer draw bar, as you lower the quill the draw dissappears inside the head.

Just some thoughts

Paul

 

[b.lindsey]

I agree with the comments thus far and being in a university machine shop lab type environment every day, there is a strong tendency to overtighten the drawbar. The one thing that should NOT be done is to unthread the drawbar entirely from the collet and then hit it, as this can damage the threads in the collet.

Bill

 

[GerryR]

.....is there a way around hitting it, like using a drawbar that is captive with a left-hand nut so that, as you loosen the drawbar, it comes up against the nut and can't go any further, forcing the collet down?

Opinions please?

Thanks,


Nelson

My Hedwick Miller has this exact set-up. Never have to "get tough" with the old girl.

 

[8ntsane]

Gerry
Any chance of posting pic of that set up. Cant say Ive seen that before. Does that bar have a combo of LH & RH threads?
Iterested to see that set up of yours.

Paul

 

[GerryR]

The top of the drawbar is .375 Square that the LH nut fits over and screws into the splined shaft. There is a collar on the drawbar that stops the drawbar from moving up when unscrewed, forcing the R8 collet down. Really simple; no hammer required.

 

[BRIAN]

On the Chester 16v the draw bar is retained in position by a cap, screwed to the top of the quill,
leaving the draw bar with 1/16"end play. So it tightens as normal, but when you loosen the draw bar
hits the cap and ejects the taper.

Brian.