Which Drill Bit for Steel

Beltzington · May 12, 2014

What types of bits do you metal mavens typically use with your hand drills? Here is my recent experience drilling 12 1/4" holes in 3/8" mild steel:

Dewalt Cobalt ($$$) Cut well but broke three bits in 5 holes

Irwin Black Oxide ($) Dulled quickly but managed to complete the remaining 7 holes using four bits

Dewalt Titanium ($$) Did not try

Mineral oil (messy) and WD-40 improved the drilling I did not have actual cutting fluid. I am sure a drill press would prevent or reduce snapping the bit but this is not an option.

Appreciate your experiences

Soundguy · May 12, 2014

Good grief! if you are breaking bits, you are likely flexing or moving the bit while it is piloted in the hole.. that's the problem with using a hand drill.. you have to hold it steady.

1/4" mild steel 12 holes used 7 bits? WOW.

simple HSS and cutting oil should have done it with 1 bit. Manage heat,, oil is cheap...

Beltzington · May 12, 2014

Soundguy said:
Good grief! if you are breaking bits, you are likely flexing or moving the bit while it is piloted in the hole.. that's the problem with using a hand drill.. you have to hold it steady.

You think Capt. obvious?

How about some real advice? What is HSS High Speed Steel? Do you have a favored brand?

Soundguy · May 12, 2014

Beltzington said:
You think Capt. obvious?

How about some real advice? What is HSS High Speed Steel? Do you have a favored brand?

How about some real advice? Um.. I gave you real advice.. both on drill type and technique.... here's some more.. how about not being rude to those helping you?

I'm putting you on ignore now after that rude comment.

good luck with the 7 bits per 12 hole ratio... wish i owned a drill bit store.

Raspy · May 12, 2014

Soundguy has it right.

One HSS or titanium bit, or equivalent should have done them all with ease.

Hold the drill motor steady with both hands so it's not bending the drill bit or can't twist when it gets stuck. Apply enough pressure to get a curl of cut metal once the drill gets established and gets deep enough for full flute contact. Slow speed is better than a very high speed to prevent heat. Any handy oil will help. Motor oil is good, drill slow enough that it doesn't get slung away (if you don't have any, pull the dipstick on your tractor and touch the end on your mark). Ease the feed force as the drill begins to break through the other side to prevent getting stuck or breaking the drill.

The best way to do this is to put your steel on the floor on a piece of wood. Put both knees down on the floor and get a solid grip on the motor. A couple drops of oil on your mark. Feed with steady pressure and look for the curl. Not much pressure is required for 1/4". If the bit gets stuck, hit reverse to get it free, then come in again at full RPM and very little pressure.

If you are drilling stainless, you must have a curl or the metal will work harden and ruin the drill.

Beltzington · May 12, 2014

Sounds like Soundguy is a tad sensitive this morning. I know I broke the bits because of the poor control of the drill, very awkward position, I was drilling inside of a metal cabinet one handed at an angle with a 1/2" drill. That being explained I still managed to complete the remaining 7-holes with black oxide bits which did not snap. My assumption is some bits or much more brittle than others leading to my question. Which type drill bits (brand) have you folks had good experience with?

SPYDERLK · May 12, 2014

Do not push the drill motor using its handle. Use a hand on the back directly in line with the bit. If youre not good feeling imminent breakout try one of the clutch settings to prevent overtorque. If no clutch, moderate chuck tightness can be used at some cost to the bit shank.
larry

sal64 · May 12, 2014

Jobber Length Drill Bits | MSCDirect.com

varmint · May 12, 2014

Wow... this can only get better. HHS bits and, perhaps, a bit of lubricating oil (motor oil will work if nothing better is available) and you should be good to go. If the bits are dull or mis-sharpened, then sure, there will be trouble. But a new bit- oughta be a piece of cake. Cobalt bits are intended for drilling into stainless steel. Like others observed, pushing straight into the hole is critical, and some pressure will be required to advance the bit. Mild steel should drill nicely.