Hi Steve,
Put a 1/8" bit in your motor tool. A ball mill is
fine. Turn the tool on. Look at the tip of the bit as you
increase the speed. You will see the tip of the bit grow
larger. Even if you hold the motor tool tight the tip will
spin out of round. Under a florescent the Think and Tinker
bit seems to have two tips. As I slow the tool down the tip
becomes one point again. I hope to buy a new Dremel tool.
I am curious if the bearing is worn or if all Dremels are this bad.
The problem showed up when I started milling circuit boards at 20,000
RPM with a feedrate of 8" a minute. For now I dropped back to
running the Dremel on number 3 only. The Dremel has 100 hours on
it and it owes me nothing.
I bet other tools have the same problem. There is a reason
cheap machines have a top speed of 10,000 to 15,000 rpms. Going
higher gets expensive.
John
--- In Homebrew_PCBs@y..., Steve Greenfield <alienrelics@y...> wrote:
> How 'bout this little thing? Too much weight to put in a plotter,
> but maybe in a homebuilt router/engraver.
>
> http://www.harborfreight.com/cpi/ctaf/Displayitem.taf?
itemnumber=43155
>
> 58,000rpm no load. There is a Harbor Freight Tools about 1/2 mile
> from my house.
>
> How are you guys measuring runout? Drill with a stiff bit then
> measure the size of the hole? I don't have a micrometer that can
> measure the inside of a round hole.
>
> Steve Greenfield
>
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