[TheForge] HELP---Drilling A-R Plate

[Washington, Aubrey O.]

Frosty,

I hate to admit it, but you know a lot of stuff.  So, my old post drill might do just fine on spring steel but wouldn't do jack on A-R.  Makes sense.  Good thing I don't have any plans to use A-R for anything.  (Though I do have a torch....)

Good luck, Richard!

Aubrey

________________________________________
From: theforge-bounces at mailman.qth.net [theforge-bounces at mailman.qth.net] On Behalf Of Jerry Frost [akfrosty at mtaonline.net]
Sent: Thursday, September 04, 2008 12:39 PM
To: Blacksmithing List Sponsored by ABANA
Subject: Re: [TheForge] HELP---Drilling A-R Plate

RPM and feed speed are not the issue when trying to
drill A-R, Abrasion Resistant, materials it's the
abrasion resistance. This is not accomplished by using
a hard alloy, it's typically accomplished by the
addition of grains of super hard materials like
carbide, tungsten carbide in rare applications diamond,
in a specifically designed impact resistant matrix
metal.

It seems counter intuitive but the harder the material
the AR has to deal with the softer and more resilient
the matrix has to be. This is so it wears away leaving
the carbide, tungsten carbide, etc. in direct contact.
Harder matricies would ship away under the impact
wearing faster. Dealing with softer formations though
means the harder matrix is preferable to maintain the
carbide, tungsten carbide, etc. particles.

So what happens when you try to penetrate AR materials
mechanically, saw, drill, etc. is it does it's thing as
designed. namely any erosion by the blade only effects
the matrix leaving the super hard, impact resistant
particles, carbide, tungsten carbide, etc. to eat your
bits.

Using a carbide bit sounds workable unfortunately the
matrix only gives under the impact, gums it up and over
heats it. The wear particles then chip out the edge and
the bit rapidly dulls.

Using diamond will work unfortunately the matrix will
gum the bits, over heating them and the diamonds will
start popping out. Using diamond on AR is a fire with
fire situation only you're stuck using the forest fire
against back fires, you're on the wrong side of the
equation. Heck, a diamond core bit or burr is nothing
but AR using diamond in a matrix.

Hot punching is the industry standard for making holes
in AR alloys. Torches are industry standard for holing
it after market. I'd still go with water jet for
precise holes though plasma might work if it isn't
deflected too much by the AR particles. Same for laser,
refraction and explosive reaction from AR particles
might make it a non-winner.

Frosty
-------------------------------
If it ain't forged
it ain't real.
Wrought iron is.
The FrostWorks

Meadow Lakes, AK.


From: "Washington, Aubrey O." <awashington at ou.edu>



I've never tried drilling hardened steel with it, but
my old fashion hand cranked post drill with down-feed
will drill a 1" hole in 1" mild steel plate (with a lot
of cranking and lube).  It requires 1/2" shank drill
bits, and I've never seen those in carbide.  But, I
have a Jacobs chuck on a 1/2" shank that I can put any
twist bit into.  Maybe I'll see how it does on leaf
spring.

Aubrey


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