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

[Jerry Frost]

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