I need to drill some holes

I need to drill some 5/16" holes through 1/2" steel plate. This is normal run of the mill plate.
The fella that I buy my steel from has quoted me $495 to drill 48 holes. He claims it is a hand drilled job.
Is this a reasonable charge? It doesn't really matter because I am going to do it myself.
I have a drill press that will probably get the job done without burning up if I take it easy. I'm looking for advice on how to drill. I'm guessing I should drill a pilot hole first then the 5/16" hole. All while using lubrication.
Am I on the right track?
thank you.
Bob
Reply to
PowerSupplyGuy
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500 bucks for 48 holes sounds pretty steep. 5/16 through mild steel? Or is it something a little tougher, like 304 stainless? In any event try these numbers: for mild steel spin the drill at about 600 RPM. For 304 about 300 RPM. I would spin the drill faster than that in my shop but I have the right drills and coolants and machines and so on. Buy a couple stub length split point cobalt drill bits. One should actually do the job just fine, but you might goof it up. Don't bother with a pilot hole. The split point drill will center itself nicely. Any half way decent hardware store will have thread cutting oil. They should have split point drills too but they will probably be the longer jobber drills. Stub length are much stiffer. The cutting oil will usually be dark. It will say sulfurized somewhere on the label. Get this stuff, even if it isn't dark. Don't use motor oil. Heavy whipping cream makes a better cutting oil than motor oil. Really. When drilling don't pussyfoot around. Keep constant pressure when drilling so that the drill is constantly making a chip. If the drill bit isn't making a chip it is not cutting and is instead rubbing a nice hard spot in the steel while at the same time polishing away the cutting edge. For 1/2 inch thick steel you should need to apply cutting oil maybe three or four times. Be careful when the drill breaks through the back side of the work, this can chip the drill bit, leave a big hanging burr, and grab the work. So when you feel the pressure decline as the drill bit exits the work back offf so that the drill bit doesn't break through real fast. You can drill into a piece of hard wood or aluminum that is under your steel plate to lessen this problem. Good luck, Eric
Reply to
etpm
And if you're drilling stainless, really Really REALLY don't pussyfoot around -- let up the pressure for one second and you've work-hardened the steel and boy, is that a pain.
Reply to
Tim Wescott
How good/heavy/expensive is your drill press?
Reply to
Jim Wilkins
It's a cheep pos that I bought out of the back of a big rig from the tool g ypsys for $29.99 probably good for a hole or two before the motor gets too hot to touch. Perhaps I should take the $500 I'm going to save and invest in a decent drill press - that is if $500 will get me there. I don't know where to get go point me in the right direction.
Reply to
PowerSupplyGuy
Nope Tim. Regular Steel.
Reply to
PowerSupplyGuy
Thank you Eric. This is just what I need.
Reply to
PowerSupplyGuy
You might look at renting a mag-drill
Reply to
BobH
You can for sure get a good drill press for 500 frog pelts. Lots of options. From new to used. I have 4 drill presses. My favorite is an old Walker-Turner that is probably older than me and I'm 61. But I have a Jet that is a good machine too. I don't recall the names on the other two. They are just workhorses and the name labels fell off long ago. I didn't pay more than 300 for any of them. Eric
Reply to
etpm
It's a cheep pos that I bought out of the back of a big rig from the tool gypsys for $29.99 probably good for a hole or two before the motor gets too hot to touch. Perhaps I should take the $500 I'm going to save and invest in a decent drill press - that is if $500 will get me there. I don't know where to get go point me in the right direction. =========================
I adapted a cheap Duracraft drill press to drilling 1/2" holes in steel beams by chiseling and rasping out the rim in the head at the top of the column and adding setscrews to clamp the head to the column at lower positions where it deflects less.
I turned the head around opposite the base to drill directly into the beam the base was clamped to. It lacks the torque to drill directly to final size but can open up holes by 1/8" or so at a time.
Otherwise I drill on my milling machine so I can't help you with a recommendation.
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The originals are fine as long as you can clamp the base to the work. I don't know about the newer copies. -jsw
Reply to
Jim Wilkins
Then you're all set.
Reply to
Tim Wescott

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