Back in 1996, I wrote to the "third hand" column of the Home Shop Machinist magazine explaining the difficulties I had in
drilling 5/8" holes out to 3/4" while I was working upside down under my Case Tractor.
Within 2 weeks after that issue got to me I had 5 replies!
Some of the guys had more than one idea. Many of them recounted problems they had had, or horror stories about others.
Later, I received both phone calls and letters. Since I had not published my address as part of the article,
all of these guys had trouble getting to me. fortunately I live I a small town, so I did receive 3 letters with only
my name and city/state in the address and one more forwarded to me by HSM. One guy used the Internet
to get my phone number.
I do want to note that I am not personally recommending any of these ideas, since the users needs to evaluate them for safety and viability.
It is amazing to me to see so many different solutions to this problem. There is something in here for everyone who might ever be faced with this need.
Start with a small pilot hole, open it up to about 3/8".
Then, grind the rake angle of the full size drill bit to
Zero degrees (or even a bit negative). This idea works because the drill bit's web is not engaged in the metal since
the pilot hole has provided clearance and the zero rake keeps the big bit from digging in.
Use a magnetic base drill.
Attach a flat plate to the work first if needed.
Use a high speed steel hole saw.
Drill a 1/4" pilot hole first and replace the drill bit in the hole saw with a
solid 1/4" pin to provide accurate centering.
Use 3 or 4 flute core drills to open up smaller pilot holes.
The core drills don't catch and dig like 2 flute twist drills.
Use tapered bridge reamers to progressively open up the hole to the finished size.
Rudy Kouhoupt, HSM contributing editor
Use the Cole Drill, which is the hand powered drilling machine described in the Machinist's third Bedside reader.
He said: "I can identify with this one since as a blacksmith of some skill, I like using the blacksmith's Post Drill
which is also hand powered."
Start with a small pilot drill , say 1/8th, then move up by eighths.
Use DoAll cutting wax (which holds better than oil).
Rent or buy a right angle drill.
This design will lessen the difficulty of alignment and reduce the effects of twisting. when the drill bit hangs up.
If you have a bench size drill press, turn the head upside down
and locate it under the machine that needs the holes drilled. (He had to drill holes under a tractor, just as I had to).
After telling one particularly serious horror story, Lee said that the guy finished the hole with a die grinder and vowed to never drill a hole bigger than 3/8" for the rest of his life!
Use a "Third Arm", a long wooden stick, through the handle of the drill motor.
Attach the handle to an immovable post. The idea here is to poke one end of a 2 1/2 foot long wooden handle through the D
handle of a large drill motor to keep the drill motor from twisting. The other end of the long handle is notched and
pinned to a heavy steel bar which is anchored to the piece to be drilled or wedged into a handy location.
Press drill bushings into a sizable plate and clamp the plate in place over the site of the hole to be.
The drill bushing will help keep the drill straight and reduce binding. Work up to the final size in several increments.