Re: [CAD_CAM_EDM_DRO] Re: spindle extensions

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...
>
>