javaguy11111 wrote:
> I just got a set of resharpened carbide bits in from drill city. I
> chuck one up into my dremel press. I snap the bit on the first hole.
> Thinking maybe I moved the board, I tried a second bit and snapped it
> as well. This was with a #81 bit. So I thought maybe I am just a
> little clumsy and try a 1/32 bit and snap it. Noticeing that the bit
> did not penetrate all the way, I thought maybe I needed a backer.
> Still no success and I snap another 1/32 bit.
>
> My guess is that the dremel just has too much slop for these bits. Any
> suggestions.
>
Wrote this the other day and saved as draft and didn't send it later.
There are a few aspects of using small bits to always keep in mind
that don't normally matter with larger bits.
You need to search through the old messages for mine on aligning
double sided boards with drill bits and drilling holes, I've really
explained how I do both cheap and simple within the last couple of
months or so. Several others also suggested similar techniques on
aligning double sided, there is plenty to read.
For the drills the answer is:
"SPEED!!!"
Almost guaranteed you are pushing down too fast for how slow the
drill is turning. Your feed rate has to be in scale with the tip
cutting rate, and even with 20K RPM the cutting rate of the nearly
microscopic
diameter bits is rather low. If you push a #80 bit in the same rate as
a .039" at the same RPM then you're going about 3 times faster for the
speed it's cutting. Even if you go half as fast on feed rate you're
doing 1.5 times vs the cutting speed. Note that the 30K RPM seems like
a hell of a lot on a Dremel. It is not too much for tiny bits. But
it's nerve racking to hear so I normally just slow the feed down. Also
note you create ultrafine dust when you use small bits at high speed
correctly, be sure and avoid and contain it as much as possible.
Chuck up a #56 or #64 bit. Now jam it into a board as fast as you
can with the drill press and see if it doesn't break too. Even your
slowest hand movements are close to this with the much smaller bit. And
hand motion is irregular, even if you make the overall motion very slow
it's jerky when going through a material. Uneven material makes for
jerky motion as it catches. It is very difficult to get any real life
out of one of these bits without a better tool than a dremel drill
press. But nowhere is the problem slop, it's your hand motion on a tool
that isn't designed to give you the precision needed for these bits. Or
poor alignment of the tool. I can just barely use them reasonably by
hand on a much larger press by bracing my hand and doing the smoothest
slowest motion. Dozens to hundreds of holes that way. Even then I
break far more than on my machine, they are too thin and brittle to be
reliably used by hand.
You can drill hundreds to thousands of holes even with resharps. But
you have to make something so you can do it well, a hand drill
press just isn't it.
And no, it's not slop either. The thousandth or two isn't a problem,
it can be traced back to misuse of the bit, either too fast a feed or
misalignment. Not slop, misalignment. You must tweak it until the
drill is exactly aligned with the motion of the press or slide. The
angle has to be exact, so the tip cuts a hole and the shaft goes exactly
through the hole. Even a tiny bit off means the tip cuts in one place
and as you push down the shaft is pushed more and more into one side of
the hole. The alignment was just as bad with a larger bit, they can
just take the strain and side cut a bit better. You cannot properly
align with a larger bit, you simply won't see the errors until you get a
#80 or so in there. That it cut ok with larger bits just means they
could take it. My homemade CNC has tons of play, I can probably deflect
the bit 1/4" or more in either direction by hand. Yet it doesn't snap
bits, and its overall accuracy is rather high because it has so little
sideways forces when drilling. And it is not only not impossible, it's
quite easy to get superb alignment if that's what you set out to do. If
you don't bother, you'll be talking a lot about how your tools have so
much play.
Note that your approach to solving problems like this needs adjusting
too, not just this particular problem needs solving. While you can be
slack with larger bits, there's an absolute assload of small variables
that come into play when you shrink the scale down so much and have
substantially weaker bits. Far too many to be making assumptions like
'it's the drill' without even checking them. Feed rate, tip speed, and
alignment are
the three main factors for any drill, so most problems stem from one of
them not being correct. Only rarely is a secondary factor at fault.
Note that VERY OFTEN when others say they changed tools, and that the
new tool fixed it, they don't even LOOK for what the real problem was.
So what the new tool doesn't snap bits. That does not mean that the old
tool had too much slop. Far more likely that the new tool has better
basic alignment than much less play, and the owner just didn't bother to
correct the alignment of the first tool. Or a better feed mechanism
that lets them feed more smoothly. I don't have these problems even
though much of my equipment is homemade and has far more play than a
dremel. But I've precisely trued the alignment to the motion. Once the
bit starts drilling it stays in the hole, couldn't care less if there's
a few thousandths of play in the tool after it starts. Hole may be a
few thousandths
off from where it was supposed to be, but a little play doesn't snap the
bits. Even a tiny misalignment vs motion does since it flexes the tool
on every rotation.
As always, 'It's YOUR fault.' Only when you've gone through
EVERYTHING and absolutely proven that it's not your fault is it not.
Then it just might be the tool. Even then you're almost always wrong
and it really is still your fault. Tools are inanimate objects, so
hardly ever make any mistakes, unlike their owners.
When something messes up for me, there is a list I follow. Me, then
tool. I hardly ever make it down the list to tool. Really it's about
ten different me's, then tool is number 11. By doing so, and
finding the real reasons and correcting whatever slip up led to the
problem, you will quickly become very good with your tools. Someone
who's good with tools can make better items with crap tools than someone
who's crap with tools can with the best tools. Work on learning the
tools even better. It's far less expensive than just buying better
tools and noticably more effective.
Alan