What The World's Been Waiting For - Yet Another Power Drawbar Design

[Hood]

Before you buy make sure it will fit, what I mean by that is the series 1 CNC with the rigid ram have the hollow ballscrew that the spindle passes through so there is no need for the spines at that part. Maybe all are not the same but mine definitely has quite a bit of un-splined shaft above the top bearing where a standard Bridgeport spindle the splines start right after the top bearing.
Hood

[kcrouch]

This seems similar to this system.
www dot mach-1tooling dot com

I have used it and it works extremely well. Very rigid and accurate. Quick tool changes too.

Kenny

[vmax549]

Resplining would not be a problem(;-) nor would be remachining the outside to fit . I do have a series 1 boss 5 ( BOSS HAWG)  converted to Mach.

I was just thinking for the average joe with a std series 1 it may be an option IF they wanted a Tool changer option. MOST don't as the R8 stuff is CHEAP CHEAP compared to QC30 or CAT30 stuff.

Just a thought, (;-) TP

[HimyKabibble]

This seems similar to this system.
www dot mach-1tooling dot com

I have used it and it works extremely well. Very rigid and accurate. Quick tool changes too.

Kenny

Kenny,

I find that system fascinating.  The pullstud mechanism is precisely what I had in mind for a future "upgrade" to my setup, and proves that it CAN be done.  What really surprises me is the very low drawbar tension - apparently only 600#?  After my testing the last few weeks, I'm amazed that's enough to securely hold an endmill in a collet.  Do you by any chance have a means of measuring (even crudely) how much torque it takes to make a 1/2" endmill slip in a collet using that setup?  I was able to do it by clamping a vise grip on a scrap endmill, and using a $5 hardware store "fish scale" to pull on the handle, then calculate the torque based on the fishscale reading and the length of the vise grip. That would be invaluable in helping me correctly calibrate my drawbar.

I'm going to read their patents and see what I can learn....

Regards,
Ray L.

[kcrouch]

Ray,
Look a little closer. They use a collar to clamp up the collet so that the drawbar is only holding the collet in place. That gives the ability to setup tools with a constant z-offset. Neat huh? Pricing is not too bad. You could get away without their release and use the one that you have too.
Kenny

[simpson36]

Resplining would not be a problem(;-) nor would be remachining the outside to fit . I do have a series 1 boss 5 ( BOSS HAWG)  converted to Mach.

I was just thinking for the average joe with a std series 1 it may be an option IF they wanted a Tool changer option. MOST don't as the R8 stuff is CHEAP CHEAP compared to QC30 or CAT30 stuff.

Just a thought, (;-) TP

I have to wonder why nobody is talking about making a spindle from sratch . . . by the time you get done all those modifications . . . .

[HimyKabibble]

Ray,
Look a little closer. They use a collar to clamp up the collet so that the drawbar is only holding the collet in place. That gives the ability to setup tools with a constant z-offset. Neat huh? Pricing is not too bad. You could get away without their release and use the one that you have too.
Kenny

Kenny,

I did notice that, but the way I read their intent, you only need to use that if you want to maintain the tool length when the collet is removed fron the spindle.  I see nothing indicating you cannot just use the collet alone if you're not concerned with maintaining tool length.

I did just perform a test on my machine.  I took the stock drawbar, removed the top spacer, and replaced it with a short stack of Belleville washers.  I then tightened the drawbar enough to give a tension of roughly 900#, and loaded my worst (dullest) 5/8" endmill, and took a heavy cut.  The endmill did not move.  I then measured the "slip torque" at about 10 foot-pounds, compared to the roughly 25-30 inch-pounds of cutting torque on the tool.

Regards,
Ray L.

[HimyKabibble]

Resplining would not be a problem(;-) nor would be remachining the outside to fit . I do have a series 1 boss 5 ( BOSS HAWG)  converted to Mach.

I was just thinking for the average joe with a std series 1 it may be an option IF they wanted a Tool changer option. MOST don't as the R8 stuff is CHEAP CHEAP compared to QC30 or CAT30 stuff.

Just a thought, (;-) TP

I have to wonder why nobody is talking about making a spindle from sratch . . . by the time you get done all those modifications . . . .

You mean aside from the fact that it would be stupid expensive?  I sure don't have the equipment to do it.  You'd start with a couple hundred $ worth of good stock (~4" dia. by 3 feet long?), get it turned, precision bored, broached, then hardened and precision ground, inside and out.  By the time you were done, I'd guess you'd have easily $1000 in it, and have no guarantee it would even work.

This does, however, suggest a trivial solution.  If the required tension is truly only 600#, I would have no problem at all applying that force to the spindle bearings - they're MORE than large enough to handle that with ease.  A *slightly* longer drawbar (perhaps 2") could then be constructed to accomodate a stack of Belleville washers to provide the 600# tension.  Just like this thing, releasing the tool would require nothing more than mounting a "cap" over the top of the spindle that would contact the drawbar about 0.100" *before* the spindle hits the upper limit of travel.  Run the spindle all the way up, and the tool releases.  It doesn't get any simpler than that!

This, of course, is all based on that 600# being a good number.  I'm gonna have to do more tests this weekend....

Regards,
Ray L.

[kcrouch]

Ray,
I would change the Mach1 release mechanism for yours. That way a bad move or z axis runaway won't let a tool loose in your shop.
The collar definitely adds to the turning torque resistance applied to the cutter. You get the clamping force of the cutter nut added to the drawbar force. They also use a clamp collar to the spindle for very heavy loads. I have seen lots of shops use the collet clamp sleeve without the nut for many smaller cutter sizes.
Kenny

[HimyKabibble]

Ray,
I would change the Mach1 release mechanism for yours. That way a bad move or z axis runaway won't let a tool loose in your shop.
The collar definitely adds to the turning torque resistance applied to the cutter. You get the clamping force of the cutter nut added to the drawbar force. They also use a clamp collar to the spindle for very heavy loads. I have seen lots of shops use the collet clamp sleeve without the nut for many smaller cutter sizes.
Kenny

Kenny,

I am VERY glad you posted the link to the Mach1 drawbar.  It has forced me to re-evaluate what I've done, and I found a significant error in one of my base assumptions.  I'm going to go do some thinking, but I think I can see how to resolve the problems I have with my current design.  This will, I think, let me greatly shorten the drawbar and guide tube, and, with luck, eliminate the balance/runout/whipping issues.

Regards,
Ray L.