Re: Cheap 56,000RPM milling upgrade (not a dremel :)

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Abby Katt" <cnc@a...> wrote:

> Hi all,
>
> I found this great link while looking around, for about $150 you can
> basically get a air-powered mini die grinder and hold it in a collet

on your

> mill with a special hollow drawbar for the air intake. This way you get
> 56,000RPM milling for 2/16" (3MM) and smaller end-mills. But you'll

need a

> beefy compressor... You need 28CFM to run it 100% duty cycle, but I

think if

> you turned down the pressure you'd just get a little bit lower rate.
>
> http://www.homemetalshopclub.org/news/feb04/feb04.html#mill
>
> For those of you in the UK, I found one for < 100 pounds
>
> http://www.cromwell.co.uk/KBE2702543K?popup=yes
>
> Just Google or Froogle for "micro die grinder".
> I remember finding something similar (but bigger) for about $500,

which had

> an air inlet on the side, and a centrally aligned stub which would

fit into

> a collet, but this mini-mod seems a lot better/economical for the hobby
> CNCist. With a 3mm ballnose cutter you'd be able to cut at a rate of

like

> 1.5M/mm! As it is anyway, I only tend to need the high speeds for small
> cutters, this would be ideal for parallel finishing on engravings.
>
> Not affiliated with any of these guys, just seemed a very good idea.
> Especially since it's a lot more realistic than trying to make my

own pulley

> for my desktop mill to try and get 4000RPM out of bearings only rated to
> 2100.
>
> (Don't forget to wear goggles or, best yet, have a cabinet around

your CNC

> if you start running your endmills at these high speeds. When they ping,
> they automatically home towards your face/eyes/soft tissue.
>
> ~Abby

Hi Abbey - Just a small note of caution:
I have the very same Taiwanese micro die grinder they are using.
(from Harbor Frieght ~$30) It works great as a dremel type
replacement, but it isn't very powerful, and mine has gotten pretty
lose, at least several thousandths axial and radial play after maybe
4-5 hours of total use. It may work fine, but I would't be terribly
surprised if you had trouble milling with it.

- Cameron