On 22 Feb 2016 07:55:32 -0800, you wrote:
>How much runout does it have? And, how much runout is too much.?
Some of this you can see. (for the too much) My opinion is that if
you can see the drill wobble, (and especially if the very fine drill
wobbles more than its own diameter), that's too much.
>
>I ask this because while I was in the process of building a inverted drill (to drill PCBs from the bottom up) at one point I had a runout of at least .01 inches. This is probably much more than your average Dremel. Despite this I was able to drill holes down to .0225 (#74 drill) using carbide drills without breaking any bits. Admittedly I was using 45X magnification to align the board and was watching as the drill broke through, therefore I did not plunge the drills to half or more of their length.
Runout in such a design can come from at least four sources: 1) drill
being bent; 2) collet wobble; 3) bearing wobble; and 4) mount wobble.
I built one, too (and highly recommend the design if you can do it).
1) bent drills are unlikely in carbide
2) collets made from aluminum (dremel) are more likely to be deformed
and inaccurate, while hardened steel chucks or steel collets (example:
proxxon) are less likely to be deformed. I also suspect that proxxon
engineers to a higher standard.
3) ditto on the bearings
4) I used a linear table, one dimension, and relatively thick aluminum
(at least 1/4 inch) for support. I also used a linear stepper for the
drive, so it was not a factor (the table would have swamped any
variation).
Given that (and that the depth of penetration is settable), I've had
no problems with drill breaking.
>
>I seriously doubt that the problem people are having with drill breakage using Dremels is due simply to runout. I also don't doubt that they are having better results with other tools such as Proxxon rotary tools.
>
Yep. The mounts for the drills, if unsteady, and allowing sideways
movement while drilling, will also cause problems.
>The reason I mention this is that it would be difficult for the average person to improve the runout of tools such as the Dremel but if another cause for drill breakage was found perhaps that could be easily corrected.
Ancient fix for car problems: remove licence plates, replace
intervening material, replace licence plates.
I'd say that if the collets and chucks can't be improved, and
replacement of the tool is not desired, then I would concentrate on
the mount for wobble.
Harvey
>
>Craig