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Posted to rec.crafts.metalworking
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Spindle repair
Larry Jaques wrote:
On Fri, 19 Jul 2013 10:59:00 -0500, "Pete C."
wrote:
Larry Jaques wrote:
On Fri, 19 Jul 2013 07:18:03 -0700, Gunner Asch
wrote:
On Fri, 19 Jul 2013 05:57:31 -0700, Larry Jaques
wrote:
On Fri, 19 Jul 2013 05:33:17 -0500, Karl Townsend
wrote:
...
How is the CNC drawbar engaged? (curious) I thought drawbars were
just glorified, dual-threaded long bolts which engaged the bit from
the top, drawing it into the tapered spindle hole.
power drawbars have splined ends with points on the end of the
splines. There's a female mating spline on an electric impact wrench
and an air cylinder to drop it in place.
OK, that covers the top end, but what about the bottom? Are the bit
adapters tapered and do they have threaded tops like their manual
counterparts? I don't yet grok the mating method, -especially- after
seeing the spindle parts you showed. I only saw female bottoms, if you
will. (quiet, Mikey. 
http://www.ebay.com/itm/Emuge-CAT-40...-/261218374005
Look for the round gizmo sticking out of the top end of the tool
holder.
And a slightly different type
http://www.ebay.com/itm/SECO-EPB-GRA...-/181175831504
This is a pull stud that gets screwed into the end of a tool holder
http://www.shop.yourtoolingstore.com...45PullStud.jpg
So there's a grasping mechanism in the spindle which grabs that
button? Or levers to wedge it upwards, seating the tapers together?
Got any photos of cutaways or exploded diagrams? They're always
easiest on my grokker.
It's an ordinary threaded drawbar - a long glorified bolt. The only
difference is that it is driven by an impact wrench instead of manually
with a hand wrench. Pretty much all the older CNC adaptations of manual
mills were like this, and those power drawbars were also used on manual
mills that were large enough to be a pain to reach the drawbar manually.
Modern CNC machines use a drawbar with a collet that grabs a pull stud
on the tool holder. No rotation, just linear action. The retention force
comes from a stack of belville spring washers on the drawbar. A
hydraulic actuator pushes the drawbar down compressing the spring
washers and allowing the collet to release the pull stud.
That pretty much reiterates the same info, Pete. What my grokker is
crying out for is the method of actuation. What does the linear
action work on? Does a tapered cone come down onto the retention feet,
or do(es) the feet/foot pivot?
And what actuates the mechanical portion of that? Pneumatics,
hydraulics, what? Thanks in advance.
http://www.techniksusa.com/metal/holder_maintenance.htm
http://www.compumachine.com/Support/...0_VMC_4020.pdf
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