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Cutting A Hole In A Steel Door
How do you install a door knob on a
metal door? What tool to you use to cut through the steel?
I've
never drilled a new hole for an additional door knob or deadbolt
on a steel door. I have ordered doors with the extra hole already
punched, which is the standard practice in new construction.
However, there must be a way. Obviously a hole saw of the proper
size needs to be used. I can't remember what the standard hole
size is, and I don't feel like removing one of my door knobs just
to measure! I think it's 2-1/8" diameter.
Anyways, my approach would be buy a good quality BI-METAL hole
saw. Expect to pay $15 or more, it's money well spent. I would
remove the door and lay it on saw horses, with some sort of
padding to prevent scratching the paint.
I would lay out the the holes in the face using whatever template
came with the knob/deadbolt, and drill carefully. There is a trick
to drilling and cutting in steel. Most people drill way too fast
and don't press down hard enough. But proper cutting in steel
demands a pretty slow speed (maybe 200 rpm for this application),
lots of downward pressure, and LOTS OF LUBRICANT. I use things
like WD-40 or chain-and-cable spray lube. Anything that cools the
cutting teeth will help, even plain water, but that will help rust
form. Holding the drill steady for this task is kinda difficult,
it really takes two hands. I prefer to have a helper spray the
lubricant on the teeth as I drill. When the lubricant smokes, you
know the teeth are getting hot. Without lubricant you will almost
certainly overheat the teeth, which will change the chemical
structure of the steel and dull the blade within a few minutes.
The other problem is cutting the hole(s) on the edge of the door.
Depending on the door's construction, you may or may not need to
do some fancy metal cutting to get the rectangular cut-out that
the latch MAY require. Some door latches only need a round hole
(7/8" diameter I think). This hole may also require that you
obtain a hole saw. You cannot use an ordinary spade bit to cut
steel. You can use a so-called "twist drill" bit to cut
a hole that big, but good luck finding one 7/8" in diameter,
it would require an enormous drill motor, and if you could get the
bit spinning it could break your wrist when the cutting face snags
on the edge of the metal.
You might be able to do some or all of this cutting with a Dremel
tool, but it could take a long time, perhaps several hours.
If you're lucky you might have door with a wooden edge that can be
drilled with a simple spade bit. Steel doors aren't very
"handyman friendly". I've never known someone to cut
a new hole. It might be easier and cheaper to buy a new door,
without the jamb, with the holes already punched.
Bruce W. Maki, Editor.
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