What are the strongest drill bits for steel?

[6mmintl]

Dark high sulfur pipe threading oil, and or add moly.

[Jismah]

Depending on the material that you are drilling, HSS is probably your best all-around choice.
For plastic, aluminum and light gauge steel, the price/longevity ratio is tough to beat. Between fabbing stuff 5-10 times a day for the trucks at work, and general use (drilling through firewalls, extracting stuck bolts, etc), I use my bits pretty much every day. From my experience:
1. Cobalt is best, but a good HSS bit is fine if it's from a quality source. I bought a set of bits (1/16 -> 1/2 by 64ths) off one of the tool trucks at work. Ran ~$180 for the set, but the bits are warrantied for breakage, so as long as you keep them sharp it's a reasonable investment.
2. Keep them sharp. Most drill bits aren't as sharp as they could be, even out of the packaging. Learn how to use a bench grinder, or even better, a drill doctor (but get one of the higher end ones that will do split points).
3. Split points for metal is the way to go. Keeps the bit from wandering.
4. Use cutting fluid. It keeps the bit cool and prolongs the life of the bit. Heat kills bits.
5. Let the bit do the cutting, not pressure. Apply just enough pressure for the bit to work, any more than that and you are dulling the cutting edge of the bit. It sounds simple, but most people don't do it. I used to drill quite a bit of stainless while working offshore (mostly 10 ga or less). I did not find any bits that would do it "easily", Cobalt bits Irwin https://mechanicguides.com/best-cobalt-drill-bit-sets/ tend to be better. Slow speed and heavy feed pressure with ample coolant will do the job, which means that you need a drill press with appropriate speeds. If you have to drill with a portable drill, keep the speed VERY slow and press HARD.
Stainless tends to work harden so you must keep cutting through the hardened layer every revolution, if you let up on the feed for an instant, the hardened layer will be too thick and will ruin your bit..I like to watch YouTube videos of a similar subject when I'm looking for information about the right product. I hope this helps someone in the future. Good luck!

[BajaJames83]

what are ypu yryimg to drill?
those speeds sound low but it depends on the material and drill bit size

[God Bless America]

OP don't forget about spot annealing.

[freonr22]

3 year old thread. lol