On 2/11/2011 10:37 AM, PICdude wrote:
> Quoting Carl Denk<cdenk@windstream.net>:
>
>   =20
>>> The Dremel won't work either -- the router bit gets clogged with bits o=
f
>>> PVC very, VERY quickly and just plain stops cutting. I suspect my PCB
>>> router bit isn't geared up for uPVC, or the Dremel is moving too fast
>>> and melting the plastic (not surprising).
>>>
>>>       =20
>> Wrong bit, one I suggested has about 1.5" cutting length, the flutes
>> (grooves) are sharpened, and the spiral ejects chips. Try lower speed,
>> maybe using 1/4" electric drill. Speed will melt plastic, and make a mes=
s.
>>     =20
>
> Will have to disagree with this.  Cutting at almost any speed will
> generate enough heat to melt the plastic, as the bit lingers in the
> just-cut area.  The way to not melt the plastic is to move out of the
> area just cut as quickly as possible, so that means faster feed rate.
> And that means faster spindle speed.  Yes, that also means greater
> side load on the spindle bearings, so the way to compensate for that
> is to take shallower cuts... ie: cut a few mm deep very quickly, then
> go around the same path again, but another few mm deep, etc.  This is
> fairly standard milling procedure.
>   =20
Can't disagree with that. But without, someway to guide the bit in=20
exactly the same path (not hand held) every time, it won't work. As I=20
said previously, take the time to build a jig if don't have another=20
expedient way to do it. :)
> If you can make a wooden (or other) template for the spindle
> guard-ring to ride on, so it follows the circle, this will make the
> whole process MUCH easier.  And keep it cool with WD-40 also.
>
> FWIW, you may want to cut the circle a bit smaller, then file or use a
> sanding drum to open it up slowly to the perfect shape/size.
>   =20
Agreed.
> Or if all that fails, just send it to me and I'll CNC-mill it for you.
>   =20
Nice offer. :) :)
> Cheers,
> -Neil.
>
>
>
>
>   =20
--=20
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