On 2010-04-25, Jon Danniken wrote:
DoN. Nichols wrote:
Maybe -- maybe not. What is the nameplate RPM for that motor vs
the one currently in the drill press? If it is a 4-pole motor (a bit
below 1800 RPM) and the original was a 2-pole motor (a bit below 3600
RPM) you would gain slower operation as well. (Same for other
possible ratios of pole counts on the motors.
Hi Don, thanks for your response; they are both 1725s.
So much for that possible benefit. :-)
You're forgetting the tri-lobed holes from a standard drill bit
in thin metal which was mentioned earlier.
If I go with a twist bit, I will finish it up with a reamer, a tool which I
have always been eager to play with.
Hmm ... what kind of reamer? Single size reamers are really
designed to remove very little metal from a slightly undersized hole to
produce a precise hole size. I don't think that one would work well in
a tri-lobed hole.
Or -- if you are talking about a tapered reamer, that (under
manual power) might do reasonably well. The one I'm most familiar with
goes from perhaps 3/16" to 1/2" with a T-handle. There are larger ones
designed to ream the ID of pipes to remove burrs. These are fitted with
the square shank which fits a brace (drill holder for wood bits). That,
with a brace might work well, as long as you had a way to make sure that
you stop before the hole gets too large.
But if you insist on running one -- check whether the shank has
three partial flats on it. Without those, the bit is likely to bind
and the shank slip in the chuck.
Oh man tell me about it! This Delta of mine spins a 3/8" shiny finish when
it catches at the end of a hole, and drives me NUTS!
:-)
Do you use the chuck key in all three positions? This makes for
a somewhat better grip.
Unfortunate, too, because there is a S/D bit in my size for under $10 from
Amazon (the flatted one is a Milwaukee at fifty bucks and it got a bad
review).
Perhaps the bad review is because of the relative price?
A quick plunge into MSC's online catalog search for "Cutting
Tools"/drills/Reduced shank drills" and limiting to 1/2" shank 1"
diameter, and Cobalt steel (gets you better wear life) finds six of
them, ranging from $67.70 to $121.07. None of them state whether they
have flats on the shank.
HSS has 9 bits. Price range from $31.97 to $75.79.
Looking at the illustration for MSC #00649616 (Triumph Twist
Drill) I see that this one has a split point, which would mean less
force needed to drill directly without a pilot hole. The price on this
one is $52.26.
I might just try a round shank, and see if I can pound the key
enough to lock it in place.
Try tightening it in all three key positions. That will help a
bit -- though probably not enough.
If you have a milling machine and a spin indexer, you could
machine your own flats on the shank if it turns out to not have them.
FWIW -- the flute length on these is 3" -- but if your drill
press's stroke is shorter than that, you would not want that.
Given the price range found there, the price on your Milwaukee
seems to be reasonable. What did the test report complain about?
Performance, or price compared to import bits?
You've already had one suggestion to use a Unibit, and I second
that. In case you don't know what they are -- they are a stepped
drill bit with a single flute which is self-guiding in the metal.
They come in various size ranges and step height. How thick is your
steel?
The steel is 11 gauge (0.12). I do know what a step-drill is, and actually
have one of the DrillMaster units from HF. I have always considered it to
be a bit for drilling out thin sheet metal; I originally purchased it for
making knob holes in a chassis.
It is good for material thickness up to the step length on the
particular Unibit which you have. The one which I found appears to have
a long enough step to handle your 1/8" steel.
That I have had more than a couple of suggestions to use one has garenerd my
attention, although I must admit a bit of skepticism as to whether or not it
is the right tool considering the number of holes (60 to 80) and the
thickness of material which I am looking to bore (1/8").
Try it -- you'll be surprised. Just for a test, try the
smaller one which you already have and see how it performs producing
holes up to 1/2" (or whatever its maximum is).
In any case -- instead of using water, I would suggest Rigid
high-sulfur thread cutting oil.
You won't have to remove as much metal at a pass as you would
with the Silver & Demming bit, so there is a greater chance that your
drill press will have sufficient torque -- with the above-mentioned
cutting oil refreshed for each hole. (Paint it on the unibit with an
acid brush or something similar.
Thanks for the suggestion, Don. I must admit that I really like water
because it is cheap and is easy to flow at a volume sufficient to cool the
bit and workpiece.
You use it outdoors? Indoors makes a real mess since you don't
have a way to capture and recycle the coolant. If you did, I would
suggest you use it with a soluble oil in the water -- made for steel
cutting.
I have used it before with good results in cooling, but
perhaps it is the lubrication ability of the bona fide product which makes
it shine.
The sulfur in the high sulfur cutting oil both lubricates the
chips (a high pressure lubricant) and reduces the strength of the metal
in shear where you are cutting.
Good Luck,
DoN.
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