Re: [CAD_CAM_EDM_DRO] Re: spindle extensions

Yep.....
It's bad enough just chucking a long bit in your typical wood router. it seems I
always have to put a Dial on it and "tap" a little here and there to get
straight. Obviously, the collet design was not made for such a thing let alone
extending it.
To accomodate 3d deep profiling (in my case mostly foam) I had drawn up a
rather long Tube shaped spindle. Driven by belt, it's just a simple aluminum
housing, machined to accept some decent bearings with a setscrew only toolholder
in the main shaft.

I began to rethink the overall size of what we typically build for a Z axis
plate. Why should we have a 6" or so wide plate that seems to just get in the
way for deep profile work? With such a design, we are forced to make bits hang
"out" pretty far to clear. Next time, I will only have this simple tube style
spindle move up and down for Z. This way there will only be a small profile, or
at least a much smaller profile that can get in the way of deep work.

So far, Its just a concept really. of course thats where most of my ideas end
up!

Chris L

Marcus & Eva wrote:

> Hi Ballendo:
> I read your comments with interest (as always).
> I am uncomfortable with the notion that it is possible to extend a router
> spindle with an add-on.
> As you have commented in the past, I am a bit obsessed with a desire to
> achieve maximum rigidity as a prerequisite to working acurately and safely,
> and I'd be really worried about hanging an extension out way past the front
> bearing on a spindle that's not really designed for that kind of load.
> Not only will it likely scream like the cats in the backyard while taking a
> cut; I also shudder to think what might happen if that setup lets go at 20K
> RPM.
> I know you're not really advocating that approach as a good or desirable way
> to run a CNC router, but I sure hope no one thinks that you are, and starts
> cobbling one together!!!
> The only way I'd even consider a long-nosed high speed setup is to get a
> needle roller or custom angular contact bearing snuggled right up next to
> the collet nut. (mini cartridge spindle- like the Deckel pantograph has.)
> A spindle like that has incredible ruggedness and abuse tolerance in a very
> compact package.
> I've seen 1/2" solid carbide blanks snapped off in a Deckel, and nary a burp
> from the spindle (it's less than 2" in diameter and will run to 30,000 RPM
> or so)
> Cheers
>
> Marcus
>
> > As to adding some length to a router: The newer "quick-change chucks
> > available for the Porter-cable 3-1/4 HP routers extend a significant
> > ways from the original position (so much that the base needs to
> > have "spacers" inserted). But some have complained that runout is
> > unacceptable with this tooling... Others love it. One could even
> > arrange a sort of fork off at one edge of the travel to lock/unlock
> > this type of device; the problem would be getting the tool lined up
> > with the collet accurately enough.
> >
> > I'm quite sure a GOOD/expert machinist could make an extension for
> > this type of router---I'd use the existing taper which is provided
> > for the collet, and make a "collet" that was really more like an
> > endmill holder for a milling machine, with a turned "boss" for the
> > clamping nut to act upon .The nut would be bored out somewhat)---,
> > but again, while the design might be trivial, the implementation
> > needs near perfection. We're talking SHARP bits at 20K+ RPM, here!
> >
> > By the time you do this (and balance the rotor, improve the bearings,
> > tighten up the tolerances since the loads are different) you're
> > really just re-creating the hi-freq spindle again...
> >
> >
>
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