Drilling steel

[Ron Bott]

I need to drill some 3/8" holes through some 1/4" steel. Would it be reasonable to do this with a cordless drill? I won't bring able to bring the material home a do on a drill press. Is a special bit or drill speed required? Any tips would be most appreciated.

[Dave Wagner]

If you have a good cordless, a powered drill would probably work better. GO Slow. Also make sure you clamp the piece down good, if it catches, it can be deadly or damaging (been there! scars to prove it!). Make sure you center punch to start so the bit doesn't wander.

A good drill bit and maybe some cutting fluid or WD40 to help lubricate the bit and keep it from dulling out. Just take your time and go slow.

[Jay Jeffery]

One word: Cobalt. You can drill steel with your run of the mill high-speed steel bits, but cobalt works soooooooo much better.

At Lowes, they area avaliabel individualy carded in the DeWalt brand, but don't confuse the element "cobalt" for their line of questionable quality import tools they call "Kobalt." Home Depot sells them in the Ridgid brand carded and in sets. Sears carries them in the "Craftsman Profesional" line. Just make sure they say "cobalt" on the card. You can also get a set of them at HF; the few of them I've used worked well enough.

As Mr Wagner said, go slow. You want to spin around 600 rpm or so for 3/8" in steel. Anything over 1,000 rpm will destroy wour bit. If your drill has a low gear, set it. If you just have to keep the trigger half depressed, do what you have to do to keep the speed reasonable.

Motor oil woks pretty well as a cutting oil for steel, but it shouldn't be strictly necissary for 3/8" holes in 1/4" thick plate.

A 1/4" pilot hole wouldn't be a bad idea, but again, not strictly necisary.

Good luck.

[curtis rosche]

the hardest oart is when they go through the back side, if you press too hard when it tries togo through, you will have a catch and possibly shatter bits. done this many times

[Bill White]

Step drill it. 1/4" hole first, then go to the 3/8" bit. Lube and drill slowly.
Bill

[Lee Schierer]

When people say drill slow;y they mean the rpm of he drill bit, keep is slow, the faster the bit turns the hotter it will get. The hotter it gets the faster it dulls. Drill a 1/8" hole first and then step in size about 1/8" max per step.

[Andrew Pitonyak]

When I did it, I mixed oil, water, and dish soap. Kind of over-kill I suppose. Water helps pull the heat, oil helps lubricate, and the soap helps the water and oil mix together. I opted for vegetable oil because it smells better than some other things that you can use. To get a feel for the proportions, I saw one recipe that had 1 quart motor oil, 3 cups soap, and 4 gallons water. In other words, it is mostly water (about 16:1 water to oil). The amount of soap is directly related to the soap type and how much is required to cause the two to mix. I figured this would be less flammable than straight oil. Also note that many people just use water and soap and are done with it.

For my uses, I used a babyfood jar and I only filled it about 1/4 to 1/2 full of water, dumped in a bit of oil and then some soap and I mixed. I then applied the solution using a small brush.

I used Craftsman Cobalt bits.

Only drilled four or five holes, but it worked very well. I used my Milwaukee 18V cordless drill for all holes. I used one of those drill guides that allow you to lock it in at 90 degrees and then I clamped that to the surface so it would not move while I was drilling.

[Bruce Page]

I have drilled a lot of steel. A 3/8 hole is not a big deal, just use a good quality bit. HS will work fine - cobalt is good, but not required. A pilot hole is not necessary IMO.

Clamp the work piece.
Center punch the steel to help get the cut started.
Use a light oil like 3-in-1 or even motor oil to lubricate.
Use a moderate RPM.
Use a light feed rate, and caution when the bit breaks through, to prevent it from catching.

[Steve Ryan]

Any high speed jobbers drill will work. Center punch first. Drill a pilot hole about the same diameter as the web thickness on the 3/8 drill bit. Do NOT drill a 1/4 hole first, sorry, but that may make the 3/8 drill dig in and snap. Oil is for cooling but not needed if you peck your way through.

[Andrew Joiner]

This is a job for a corded drill if you have more than one hole to drill.

[Jerome Stanek]

I've drilled thousands of holes like that and yes slow the RPM down and use oil or even wd 40

[Van Huskey]

MTW it would help to know what kind of steel, there is a lot of difference between M42 and mild steel! If it is mild steel you won't have any issues even dry but I would probably add a touch of oil to a standard twist bit, if dry let the bit cool between holes are it is going to be smoked pretty quickly.

[mickey cassiba]

I'll go with Bruce on this one...although it would be good to know the type of steel you're drilling. If your drill has an auxiliary side handle, use it. There will be a slight catch as you exit the bottom of the work. recycled motor oil makes an excellent coolant.Pilot holes can cause damage to the lips of the larger drill. Hard steel requires low rpm, high feed pressure to avoid work hardening( the friction of a quickly spinning drill coupled with light feed will harden the steel ahead of the drill. HSS is my go to, but I've used carbon steel drills as well. They tend to wear quickly, but if its not many holes, you can get by.

[Gary Kman]

I drill, mill, turn quite a bit of steel and use a store-bought cutting fluid mixed with water. Likely similar to the recipe detailed above. As long as there is water present the surfaces won't get much above 212* F. The drill can't lose it's temper and the workpiece can't work harden. Very important. Oil alone won't do this. Being careful isn't good enough when the bit exit the opposite side. Clamp down to a fresh part of a scrap board. I've easily drilled 1" holes with a hand held drill with the scrap c clamped to a farm implement. Stepping from small to large of course. A pal rebuilds wrecked cars. Drills out hundreds of welds that are harder than a politician's head. Punch, 1/8" cobalt (bought in10 packs ), 1/4" solid carbide twist drill. If you aren't seeing curls stop and see what's wrong. Enjoy.

[Rich Engelhardt]

My 18V DeWalt cordless has a drive and drill speed selector.
I use drill when drilling wood and drive when drilling metal.

[Ole Anderson]

Key to drilling steel is somewhat obvious but hasn't been mentioned. Use as much pressure as possible to get the bit to bite into the steel. That is why a drill press works so well. When drilling into the bottom of my Jeep's frame, I use levers and even a floor jack to get the pressure needed. For a 3/8" hole, with a cordless drill, I would drill a 3/16" pilot hole, then go with a 3/8". And a new or recently sharpened bit makes things go so much easier. A sharp bit and plenty of pressure and you will drill so fast that full time coolant won't be needed but I would hit the bit with some oil halfway thru each hole. Cobalt holds an edge longer but is brittle and more likely to break as you finish the hole.