bitsconcretedrillsteel
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?
No, this isn't normal. Your anchors don't fit to your screws. What is happening is that the tip of the screw reached the concrete, and, of course, you can't force a screw into concrete - not even with a drill or a electric screwdriver, and certainly not by hand.
This picture shows how anchor and screw should fit into the hole. The hole definitely needs to be longer than the screw. The screw should be a bit longer than the anchor, but not as long. Maybe the clerk saw that you have picked an wood screw and gave you anchors suited for the second situation. It doesn't hurt to use wood screws with anchors in a concrete wall, you'll just have the cap jutting out a bit. But the length of the screw should be only a bit longer than that of the anchor (the surplus should equal the length of the tip + the length of the attached thing), and your cap will stick out a bit if the thing you are attaching isn't soft enough for the cap to sink in.
The table shows how to determine the correct hole depth. It also tells you what diameter of anchor and drill to choose for a given screw. As for the length of the screw, it is determined by the weight it will have to carry. Vertical screws are more problematic than screws in walls, because gravity is pulling in the direction of the hole, not at 90° to it. Light curtains will be OK with your size screw, but don't put any molton on them.
Most drill bits sold are "high speed" drill bits intended for a variety of materials including metal (but not concrete, tile, glass or extended use in plaster or plasterboard).
If the bits are fairly sharp, you should be able to use them in the steel, assuming it is not a hardened alloy. To improve your chances, a bit of oil or cutting fluid at the cutting point will help prevent overheating. Slower is usually better.
The rust probably makes the steel weaker and easier to drill.
Best Answer
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.