Isn't the pressure mentioned used for releasing the drawbar?

Seems to me that the release pressure would need to be adequate for breaking loose the taper and could be many times the actual drawbar tension.

The force required to release the taper, even with R8, is relatively small - no more than a couple hundred pounds.  The major force is the tension required to keep the tool in place, particularly with collets.  If using a "hard" holder, like an endmill holder, much less tension is required - It appears to me that 1-2K pounds is adequate with a hard holder, particularly with a 30-taper.

Regards,
Ray L.

Ray you are correct the drwbar forces for a 30 taper run from 1-2k lbs.  You do not have to worry about collet toolholder like the r8 collet  in 30 taper there are none(;-) They all use solid holders. There are collet type holders but the tapers are solid.

Now do be advised that the 30 taper series are getting rarer every year. Most machines start at cat/BT40 type these days. But they also have a lot higher faster spindles as well. It just raises the cost of NEW holders a bit every year as they become more obsolete. AND for the most part they are NOT cheap like the r8 holders (;-)

(;-)TP

NMTB  holders are made for a draw bar , not usable for toolchanger. If your going to change spindle , go for the 40 taper.
A 3/8" air impact @ 80psi is enough to operate the draw bar.

Ed

1k to 2k drawbar tension and 3.3K release tension  . . . . . this seems to me like reasonable numbers.

In my many years of using R8, I've always had to whack the loosened drawbar with a hammer to free the collet. (the drawbar wrench qualifies as a 'hammer', incidentally  )  Releasing MT tapers requires an act of congress. 

I would err on the side of 'way too much' force for releasing any taper, even a steep solid one.

Ray you are correct the drwbar forces for a 30 taper run from 1-2k lbs.  You do not have to worry about collet toolholder like the r8 collet  in 30 taper there are none(;-) They all use solid holders. There are collet type holders but the tapers are solid.

Now do be advised that the 30 taper series are getting rarer every year. Most machines start at cat/BT40 type these days. But they also have a lot higher faster spindles as well. It just raises the cost of NEW holders a bit every year as they become more obsolete. AND for the most part they are NOT cheap like the r8 holders (;-)

(;-)TP

Terry,

Unfortunately, a 40-taper spindle is not an option.  30-taper is all that's available.  I've found several sources for 30-taper holders, and prices seem no worse than R8, though there clearly are fewer sources.  My plan would be to immediately buy a lifetime supply.  It's either that, give up on a toolchanger entirely, or buy a used VMC.

Regards,
Ray L.

1k to 2k drawbar tension and 3.3K release tension  . . . . . this seems to me like reasonable numbers.

In my many years of using R8, I've always had to whack the loosened drawbar with a hammer to free the collet. (the drawbar wrench qualifies as a 'hammer', incidentally  )  Releasing MT tapers requires an act of congress. 

I would err on the side of 'way too much' force for releasing any taper, even a steep solid one.

On my current drawbar. unscrewing the bolt actually pushes the taper out, as the drawbar assembly is pushed down by a pair of air cylinders.   There's no downforce initially, but after the drawbolt unscrews about 1/8", the socket bottoms out, and further unscrewing creates downforce.  Even with the bolt seriously OVER-tightened, it has never failed to pop out on release.  It doesn't seem to require a huge amount of force, though I have several hundred pounds available if needed.

Regards,
Ray L.

RAY if you are talking NMTB30 I agree you can buy them cheap sometimes but vary amoung manfs as to specs (;-).  BUT IF I were to do an ATC I would use CAT30 or BT30. The grip grooves for the fingers are already there and work. and the studs have already been engineered to work properly. AND those are NOT so cheap and harder to find in 30 taper.

Just my take on it, (;-) TP

I have bought some stuff from this guy, his prices seem good and shipping to the UK was also good, he has BT and CAT30 if I remember right. The ER32 collets and straight shank holder I got were exceptional quality but maybe I was just lucky. Not sure how prices compare to USA retailers or how much shipping would be.
http://www.ctctools.biz

Hood