I know I ask a question about every month hope you don't mind.
Problem: I'm building a small backhoe and I need to drill a bunch of
1" holes in 1/4" wall SQ tubing and 1/2" thick plate steel. I'm
unable to bring the parts to my mill in my shed due to size. I've been
drilling using 1/2" gear reduction drills and reduced shank drill bits
1" diameter. I'm burning up my drills, getting hand cramps and making
shoddy holes. I bought a drill guide but it doesn't fit my drill. I've
sharpened my bits (I have 5 bits that I'm rotating) and I'm using ATF
and kerosene as my cutting fluid.
Question: Any ideas how I might make drilling these holes easier and
or better in quality? The most important thing is getting holes thru
my 3"x 1/4" thick tubing aligned. I also need another new 1/2" drill
because I burned up the armature so bad that I can't dress it up.
Thanks
Sam
Someone posted a while ago about a hand-crank drill that had a clamping
arrangement and a fine-thread feed screw (googlepause...) hmmm, no hits for
"hand drill screw feed". Maybe it was in one of Lautard's books. Anyway,
it was reported to be very good at drilling big holes in hard-to-drill
materials. If you don't have too many holes left and you were going to buy
another drill anyway, maybe that'd do and you'd have a tool that might very
*very* useful in certain circumstances.
?t=73529&highlight=&sid=bd25b514ecbf76a81a8fd04a4473bf49
Unka' George [George McDuffee]
============
Merchants have no country.
The mere spot they stand on
does not constitute so strong an attachment
as that from which they draw their gains.
Thomas Jefferson (1743-1826),
U.S. president. Letter, 17 March 1814.
A tool rental place should be able to set you up with a magnetic base
drill. It looks like a small drill press with an electromagnet in
place of the stand arrangement. The bits look like hole saws. The
one I used was made by Milwaulkee. Maybe called a "rotobroach"?
good luck.
Andy
It's very difficult to put enough pressure on a hand held drill to keep
1/2" and larger bits cutting properly. And when you do get the pressure,
you need a very low speed drill to have sufficient torque to pull the
drill. If you aren't getting nice curls of swarf, you don't have enough
pressure or sharp enough drill.
I have an old Metal cased Black and Decker 1/2 drill. Spins at 200 rpm.
I slide a trimmed down 2x4 through the 'D' handle, hook a chain around
the short end of the 2x4 and the frame piece in question. Number 1 able
assistant leans on the long end of the 2x4 while I man the trigger, the
alignment square, and the oil can. Goes through 1/2" bar stock like butter.
Modat22 wrote:
I used an old all-metal Portalign clamped to the work to drill
structural steel for a home made front end loader. The pilot hole is
1/8", then 1/2", then 3/4, 7/8, etc. Brushing a little pipe threading
oil on the bit helps a lot. Once the subassemblies became large and
heavy I hung them from the rafters for precise drilling on the milling
machine.
*****************************************
In the Trades we call that an Old Man. I made one years ago out of
pipe. Two sections of pipe and a coupler. Weld a hook on one end of
the pipe. Make a sleeve that will slide over the pipe. Weld a metal
saddle to the sleeve.The saddle is made to fit over the handle of the
drill that you use. This allows you to plum the drill using the
saddle,which is welded to the sleeve. The sleeve will be able to slide
along the pipe. Using a small chain attached one end to the hook and
dead head the other end around a solid anchor point. I made each pipe
sections 24 inches longs. This allows it to fit in one of tool boxes.
You can make them any length that works for your needs.This old man
will give you all the down pressure that you need to drill holes in
difficult areas and helps with the drilling of multiple holes. I hope
that this will help.
Millwright Ron
The biggest help will be drilling a pilot hole that is about the size
of the web of the 1 inch drill. You could make a jig to assure that
the holes are aligned. Something that would clamp on the 3 inch
tubing with 1/8 or 3/16 holes to guide the pilot drill so the pilot
holes can be drilled from opposite sides of the 3 inch tubing. Once
the pilot holes are aligned, remove the jig. You should have no
problem drilling from both sides and still being aligned.
Dan
If you can support the drilling machine on axis, hole saws can work very
well. I use them to drill holes up to 1 1/2" Dia. and up to 1 1/2" deep
in mild steel. You really need pretty low speeds, like 150 rpm or so
for a 1 1/2" saw, but I use lots of pipe threading oil and get by at 345
rpms. At 1", 400 rpms should be okay.
I can get about 2 dozen 1 1/2" deep holes or 1 3/8" diameter, for
example. This is using a Starret metal cutting hole saw. I bet I
could double the saw life if I could go slower. Do a lot of "pecking"
to clear chips. In deeper holes, drill a small hole just to the inside
of the periphery of where the large hole will go This will help, but not
eliminate the need to retract (peck) the drill to clear chips. For
example, I drill a 5/16" "clearing" hole for this purpose when I drill
more than about 1/2" deep holes.
Last note: In my own experience, these hole saws drill a little
oversize, like 15 thou for a 1 3/8" saw. Holes are relatively clean,
but not perfect.
Pete Stanaitis
------------------
Modat22 wrote:
You've had some good advise on machinery to use, you need to get some
decent cutting fluid. You aren't trying to lubricate the thing,
you're trying to cut it. Get some high-sulfur cutting oil, the black,
stinky stuff they use on large pipe threading. Yeah, it's obnoxious,
but it works a whole lot better than home-made mixes. Kerosene is
good for aluminum, not steel. ATF belongs in a car.
Stan
You might want to look at a portable line boring machine. They cost the
earth considering what they are made of, and that makes me think about
making one, but I have not yet. Someone here or on a tractor forum
mentioned getting one from army surplus or the like for a more
reasonable price. With that you could drill undersized and then bore out
to the size of hole you actually want. I don't recall if we've been
through this part in a past post, but I strongly advise making your
holes suited to a bushing suited to your pins, rather than suiting your
holes to your pins (I have an old backhoe, which was not properly
greased by a prior owner, and had various other forms of abuse - but I
didn't know much about what to look for when I bought it, and the price
was "right").
If the holes are made to the pins, or the bushes are allowed to wear
past the bush and into the bush-hole, refurbishment goes from: "pull the
pins, yank the bushings, put in new bushings and pins, good as new"
to: pull the pins, yank the remains of the bushings (if any), line-bore
the bushing-holes oversize, or weld to build them up and them bore back
to original size, put in new bushings and pins"
...a difference of some hours or days and a good many cuss-words.
You might also want to get more creative with either bringing the parts
to the mill, or the mill to the parts. In a past discussion related to
this sort of thing, someone mentioned building a portable boring setup
"on the machine" using the head of a mill, and some sort of creative
temporary attachment (bolt-holes or tack welds). If you have a small
milling machine or mill-drill that permits mounting the head or column
in such a manner that the base is out of the way, you might be able to
bring that to the backhoe and get the job done. Some of the little China
mills are not far off the price of a good 1/2 drill, though I don't know
how well suited they would be to that adaptation.
I'm thinking about buying a 3/4" heavy duty gear reduction drill and
mounting it to a one of those add on mill tables and use the cross
feed on the mill table to push the drill thru the cut. I'd have to
modify the mill table to make the feed screw heavy duty.
I'm also calling around trying to rent one of those magnetic base
drill presses.
Thanks for the helpful info.
Were it me I'd use an annular cutter and a rented mag base drill.
Done a hunderd times.
Some have a spring loaded center so you center punch where you want
the hole and drill it. No pilot holes and all that crap.
I once saw a large drill with a jackscrew on the back. The workers spot
welded a U-shaped frame to a heavy steel plate to be drilled. The drill was
placed under the frame and the jackscrew backed out against the frame to put
pressure on the drill. You could do something similar with a jackscrew on
the frame to press on the back of the drill. Maybe clamp the frame to your
work piece.
Don Young
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