drilling a anhydrous knife

[milo 100]

Does anyone have a secret to drill a bigger hole in an anhydrous knife.  They are extremely hard.  What type of bit to use or other secret.  We want to go from 1/2 inch to 5/8.

[infire]

You might get it done with a carbide tipped bit like a masonary bit, but I would suggest a steady handed plasma cutter or torch, it should only be hard for a thin layer on outside, good luck!

[James22]

I've drilled grade eight bolts and into a ball bearing with a carbide bit.  Never used a masonry bit with carbides cutters in steel, but certainly have ruined several drilling concrete without a hammer drill so wouldn't have a lot of faith it would work.  Others indicate it will work, just use plenty of coolant.  Since the bits are relatively easy to find, I would definitely give them a try.  True carbide bits are expensive and not found on the local hardware shelf.

[Pupdaddy]

I don't know what kind of hardware you have close...but we've used "cobalt" bits to drill stainless steel...and I would suspect they might have a chance of cutting through an anhydrous knife.

[belarus]

Yes, a good cobalt bit should drill hardened steel.  A good 5/8" cobalt bit will be pricey and will be hard to find.

Of course, the obvious, Only drill with a drill press. tighten all three chuck holes.  drill as slow as possible.  Enough lubrication so you aren't ever smoking the lubricant.  Stop if you aren't pulling off ribbons because you are just making heat.  Also stop if the bit gets hot.  Cobalt bits can be resharpened.  Clamp it down good cause the bits will want to grab.  And wear safety goggles because a real good bit can pull some long ribbons that will go flying.

[Nebrfarmr]

I wouldn't use a drill at all.  I'd use an air die grinder with a small carbide bit to hog out the hole bigger.  Might take a little longer, but won't ruin the bit.  I can cut a bearing race right through with a die grinder & carbide bit.  Just be sure the bit is 100% carbide, not just carbide-tipped.  Should cost maybe $5-$10 for the bit.  If you don't have a die grinder, and think a drill would work OK, it might but it will be extremely slow going.  To work properly, the bit needs to spin close to 10,000 RPM.   Oh, and wear goggles.

[behog]

Drill it with a concrete bit.  Just a cheap one because it will be done for by the time you are done.  Cool it with water instead of oil. Run the bit very fast .  3000 rpm

[JJ Johnson]

Use a tapered reamer. Drill bits don't like to make holes bigger in hard iron.