i in the middle of a project for my company ,but having small problem
with drilling through 1/4 inch steel. my question is what is the best
type of drill bit to use for boring thru the side of a forklift?
The 1/4" steel might just be an pre-hardened BHN of 400-500. Normal drills
won't do it.
I cut AR400 with a plasma and just cutting HRS with a drill after pre-cutting
with a torch - is rough. Hardens the metal.
If it is a hot job - like now - try a cement drill.
If it can wait for a drill - buy a 1/4" carbide centering drill or pilot drill.
Carbide made for metal - you can get that drill red hot - and the metal and
the drill continues or starts cutting. Slow cool and it is ok.
Another method - friction heat. Put a short length of drill rod and round it
over with a file - and then use it to heat a spot. Get the spot red. Cool
slow. Then drill with a good HS steel drill.
Since the sides get banged a bit - that is likely pre-hard high BHN.
Martin H. Eastburn
@ home at Lions' Lair with our computer lionslair at consolidated dot net
TSRA, Life; NRA LOH & Patron Member, Golden Eagle, Patriot's Medal.
NRA Second Amendment Task Force Charter Founder
IHMSA and NRA Metallic Silhouette maker & member.
I've used that trick to drill a hole in bandsaw blade stock, but we
just used a plain old common nail. My understanding was that it combined
annealing the spot, along with 'sucking' a bit of the carbon outta the
saw blade into the lower carbon steel nail. Not sure if that's why it
worked, but it did.
I'd be skeptical about the nail sucking out carbon, unless your nails really
suck to begin with. But the technique works well on plain-carbon and
case-hardened simple alloys. On slower-quenching alloys it may not work at
all. It may, in fact, make things worse.
This is a common gunsmith method for drilling holes for a 'scope mount on
vintage Springfield '03 receivers. They were case-hardened and harder than
the hammers of hell.
And, ummm, why are you drilling through the side of a forklift? How
big a hole?
I assume you're using high speed steel now with no luck, so the next
step up is cobalt.
Also, make sure you're using a drill motor that's got enough speed and
torque for the job. Battery-powered drills are wonderful, but serious
work requires a cord.
I have drilled holes in such metals by heating them to red/orange with a
torch and then backing the torch off so slowly so the red spot cools
down to non-glowing over a period of 20 or 30 seconds. This will
anneal that small spot enough to drill with hi-speed bits. Obviously,
you don't want to do this if there are electrical or fuel lines in the
immediate area. This will work for carbon steels for sure and maybe for
some oil hardening alloys.
I like Martin's idea of heating the spot with a spinning shaft. I
have welded long shanks to drill bits in the lathe with this method.
The issue for you will be in holding the (red) heat long enough so the
material does anneal some.
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