drill bits

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

Mart> i in the middle of a project for my company ,but having small problem

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.

Pete Stanaitis

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thirst4knwldg wrote:

I tried that trick several times, but only failed. What's the trick behind the trick?

Nick

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.

Pete

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.

-- Ed Huntress