6

I need to drill (44) holes in (22) 1/4"-thick stainless steel plates. These are for 3"x3/8" heavy Duty Screw Anchors that will go through the plate and into the concrete.

My question is: if possible, can I use one drill bit that will make the hole through the 1/4"-thick steel plate and the concrete where the screw will be inserted? This is hard reinforced concrete.

If not, what drill bits should I use? And can I use a regular drill?

Improve this question
4
  • 1
    note aside to the concrete question, stainless steel is particularly difficult to machine. You'll want good cobalt, carbide, etc bits and a powerful variable speed drill that can turn the bit at a cutting speed while you put quite a lot of force on it. If feasible id want a drill press for this. You'll probably want a hammer drill for the concrete.
    – agentp
    Commented Mar 8, 2018 at 23:37
  • Good points. I skimmed right past the stainless part. A person can melt the edge off standard bits in a hurry by spinning them at top speed while dry on stainless.
    – isherwood
    Commented Mar 9, 2018 at 2:50
  • FYI a mag drill might be especially helpful here if this is a magnetic stainless steel plate. Also, you could consider something like a thermal lance or a plasma cutter.
    – Hari
    Commented Mar 9, 2018 at 6:22
  • If it were possible to drill through the concrete side first you might avoid some of the issues with ruining your steel-cutting bits when they hit the concrete.
    – StayOnTarget
    Commented Jun 30, 2018 at 12:08

2 Answers 2

Reset to default
8

No.

Steel bits need to be very sharp to do their job. In fact, unless you set a depth gauge just barely through the metal, you'll wreck the cutting edge with every hole when you contact concrete and need to resharpen.

Concrete bits create holes by pounding and disintegrating the material. They have cutting edges, but that's mostly to focus the impact and clear debris. They become dull over time as well, but it doesn't dramatically affect their performance.

Ideally you'll drill your plates in advance, then use them as guides for drilling the concrete. Herb Guy offers some good advice on that note: "Try to find a local welding, ironworks or machine shop. They can punch or drill those holes for faster and cheaper than you ever will and make the S/S plate hole's ø 1/8” larger so the hammer drill tip and anchor shields/wedges pass through."

Otherwise, I suggest having several of each type of bit on hand. The steel bits will need time to cool after several holes (unless you lubricate with oil), so you'll want to rotate them, and the concrete bits occasionally throw their carbide teeth.

Improve this answer
0
4

If you mean non-magnetic , eg 304. stainless , you have a problem. I am assuming a limited amount of experience. If the drill turns without cutting , it coldworks the stainless making it even more difficult to cut. I would say get several 1/8" bits and several 3/8" drill bits. The "chisel" at the center of the point scrapes metal away instead of cutting it so you want it as small as possible. You make a small hole first ( and smaller than 1/8 would be good.) Low RPM, high pressure, high sulfur cutting oil, if a bit is not very sharp, change it or sharpen it. If any bit touches the concrete, it is ruined.As isherwood says you need to drill the metal before it is on the concrete. High Speed Steel bits will keep cutting up to 1000 F , so the big problem is the bit must cut and not slip/spin. Sorry for duplication. If it is magnetic stainless , eg. 410. it will not be quite as bad because the workhardening is not as extreme.

Improve this answer

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.