Re: [CAD_CAM_EDM_DRO] My first CNC mill

Congratulations! The feeling of "Now I can make _anything_!" is hard to
describe. I few things I've learned:

Dremels make poor spindles. I tried 3 before I found one with minimal run
out. I now believe it was really the collets that caused the run
out. Initially, I just wanted to drill 0.030" holes in PCB material. In
this case, you needed almost no run out to keep from breaking carbide drill
bits. I've never put any side loads on my dremel; I replaced it with a $39
orange Harbor Freight trim router (frequently on sale for $19.95).

I spent too much $ on dremel bits, only to find that everyone I've tried
was inappropriate for what I wanted to do. I guess they are O.K. for
carving wooden ducks or something. Somebody buys them...

Carpet tape is good for holding down what you are cutting. The double
sided sticky stuff. I found two kinds at Home Depot. One has more fibers
in it, and is harder to remove afterwards.

Don't try to be too cheap (like I was) with the carpet tape. After ruining
too many parts, I cover the entire bottom with tape. It's a bummer to be
almost finished with a part only to have it come loose.

At first I tried to practice engraving on scraps of plastic and old
CD-ROMs, only to have the plastic to melt around my cutter. It needs a
coolant. Water would probably be fine. I use CoolMist, 4 Oz to 1 gal of
water. It was something like $25 for a gallon of the stuff, it it's been
lasting me for ever.

Used printed circuit board drill bits make acceptable cutters, if you are
cutting out flat panels of aluminum. I use mostly 3/32" drill bits, and
1/16" bits when I need tight corners. You probably can't spin them fast
enough, and when cutting aluminum they _need_ coolant like above. I spin a
3/32" carbide drill bit at about 30,000 rpm, take 0.015" deep cuts, and
move it between 7 and 15 ipm (I've learned to 'hear' when it's cutting
nicely and not just smushing the aluminum away). Without coolant, it just
smears the aluminum away, melting it.

I'm currently using the orange $39.95 trim router from Harbor Freight
(frequently on sale for $19.95). I knew they would be low quality, and I
planned on upgrading to a name brand after I got the other bugs worked out
of my x-y table. But It's worked so well for what I use that machine for,
I may just keep using them. This trim router takes 1/4" shank bits, and I
use a 2 flute TiN coated carbide end mill for cutting aluminum. I also use
a home made 1/8" collet for my carbide PCB drill bits. I think I finally
wore out the bearings last night. Good thing I bought two of them! But
after _at least_ 100 hours on it, I sure got my $s worth. I use a variac
to control the speed of this router.

If you email me your postal address off-line, I'll try to make a trip to
the post office and give you some 3/32" carbide drill bits.

Have fun!

- Steven Ciciora

At 05:21 AM 6/3/2004 +0000, you wrote:

>I finally did it, after a year of brain brewing, I built a mostly
>homebrew CNC mill. Check out the setup at
>http://www28.brinkster.com/causticreations/cnc/cnc1.jpg Sorry if I
>run out of bandwidth, it's a brinkster site, what can I say. It was
>made with tender care on a scroll saw and drill press, out of 4 ply
>wood for less than $100 (not including the scrounged industrial
>equipment such as linear slides and complete X axis assembly), so it
>should give the cheap schmough hope. It suffers from a few problems
>though... flexible Z axis column, should have made it from 1" MDF.
>Super slow Z and Y axis caused by cheap surplus steppers with 48
>steps/rev and barbaric stepper control which is parallel port signals
>to bipolar transistors to windings. Finally, crappy dremel spindle
>that won't be replaced until previous problems solved. Other than
>that, I'd say it's pretty successful for a cheap homebrew.