I've used the "two people with a pipe and chain" method. Works OK, hate
to duplicate it for 225 holes! Run the pipe through the 'D' handle on a
1/2" 200rpm drill. weld a suitable chain hook on the end of a 4' pipe,
hook the chain around the frame, position the drill about a foot from
the chain. Operator 1 lines things up, keeps his hand on the switch,
squirts in the lube, handles the break through problem. Operator 2
leans into the pipe, has a 3 to 1 force advantage to keep the chips
coming. The secret is to keep the cutting action going at all times, if
it skates, you are done.
Wayne Cook wrote:
On Thu, 29 Dec 2005 00:14:10 -0600, "B.B."
u wrote:
OK, let's say you're given the task of making a 5/8" hole in a truck
frame (heat treated alloy steel) rail. You have at your disposal a
center punch, an air drill and what ever the hell you can chuck in the
end of it. 1/2" chuck. As a metalworker, how would you go about it?
Any torching is a big no-no.
I center punched, drilled a little hole, enlarged it to a 3/8 hole,
then used a "bridge reamer" to make it a 5/8" hole. This was a
harrowing experience because it was a mother****er to put that initial
hole in there, (had to apply a lot of pressure from a really
uncomfortable stance) and that reamer (on loan and rather pricey) had a
nasty habit of grabbing if I didn't hold it exactly straight through the
entire cut. I made it without hurting the reamer or breaking my wrists,
but I'd like to know if there is a better way.
Also, one hole was stubborn. I was going to enlarge it one more time
to a half inch, but about half way though the hole I suddenly stopped
making progress. For the life of me I could not make the damn drill cut
no matter how much pressure I applied. Just in case there was something
wrong with the bit that I couldn't see visually, I tried another, but it
wouldn't cut either. The original bit in another hole cut just fine.
HSS drill bit. The reamer (also HSS) handled that stubborn hole just
fine. So, what the hell? Did it harden on me? I wasn't building up
much heat at all. I could pull the drill out of the hole and grab the
bit and while hot, it didn't burn me.
BTW, my "cutting fluid" was 50wt transmission oil because that's all
I had, and was recommended by the guy who loaned me the reamer. It
worked, but probably isn't optimal. For next time, what (obtainable)
fluid is suggested?
I'm afraid you won't like my answer.
http://www.metalworking.com/DropBox/...xtension07.jpg
I drilled 225+ holes in that frame with that setup. I've also got a
mag drill now but I feel that the air drill setup is lighter and
easier to use. Unfortunately I can't tell you where to find another
drill like that. It's the only one I've ever seen.
Now for something that might actually help.
Drilling in one shot is always better than step drilling. The catch
is that you have to be able to put enough pressure to maintain cut
(impossible to do by hand). The next best is to drill a small hole
about the same size as the web of the big drill bit first and then go
straight to the big drill bit. However larger holes it can still be
hard to get enough pressure by hand.
The real key is to use some method of getting the pressure needed.
My setup is easy since the drill already has a jack screw built in.
You might look into building a dead man with the jack screw in it and
use a drill where you can put a little center in the back of it
(inline with the drill bit) and use that to push.
I've heard about but not used other methods (partly because some of
them are more than a little scary sounding to me). These include
wrapping a chain around the frame and looping it over the shoulder pad
on the drill (this calls for one of the old style "killer" electric
drills). Twisting the drill will cause the chain to tighten pushing
the bit in. Another method I've heard of is to use two people. One
holds the drill and another has a lever (pipe or wood) where one end
is chained to the frame, the drill is somewhere near the chain and the
second person pushes on the end of the lever. Neither method gives
enough control in my opinion.
Wayne Cook
Shamrock, TX
http://members.dslextreme.com/users/waynecook/index.htm