In article ,
"Jon Danniken" wrote:

Note: apologies if this is a dupe; eternal september is living up to it's
name....

DoN. Nichols wrote:
[snip]
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.

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!

I have a Delta DP-350, and the chuck it came with is useless. I had to replace
the chuck with a Jacobs. I've heard that Rohm chucks are good too.


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). I might just try a round shank, and see if I can pound the key
enough to lock it in place.

Tighten using all three key holes one after another. But it will still likely
spin free. I never could get the OEM chuck to grip firmly enough.


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.

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").

I have used Irwin Unibits in thick steel sheet. They work just fine. But you
do need lubrication. I typically use black sulfur oil for steel and stainlesss
steel, and denatured alcohol for aluminum. Or water-soluble oil for all metals
listed.

I would not attempt to use a 1" twist drill in such a small machine, even if
slipping could be prevented. And in a big enough machine, when the bit caught,
it would swing the tubing and smack you, hard. The workpiece must be somehow
clamped to the drillpress table.

Even with a unibit, the workpiece must be clamped somehow.


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. 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.

While water is certainly convenient, I would not use water for this.

DoN is right. Use black sulfur oil, which is made for exactly this purpose, and
is cheap and widely available. Lubrication is the issue, plus chemistry. The
sulfur is there for a reason. Cooling is less of an issue with HSS tools.

Many hardware stores carry black sulfur cutting oil, as does Home Despot (may be
in plumbing, may be in hardware), and all plumbing supply houses. There are
many brands. You will also want a small brush for applying the oil. The
traditional approach is to use a seamless steel tuna can and an acid brush.
Seamless is good because the oil will seep through the seals in some kinds of
tin can. Steel is good because the sulfur in the oil will stain non-ferrous
alloys.


Given the number of large holes to made, I have to ask why you don't just get a
larger and stronger drill press.


Joe Gwinn