Best drillbit for steel

SPYDERLK · Jul 9, 2014

LD1 said:
Drill press or hand drill.....depends. The lube isnt so much to lube the bit. ITs to keep it cool and keep the chips from galling and sticking to the bit.

IF using a drill press, your holes should take ~20 seconds to drill each. One good application at the start of each hole should be sufficient.

If using a hand or mag drill, maybe once every 20-30 seconds. Depending on the type of fluid. There is some that is thin and runs away. Others are thick like honey and stay on the part/bit longer.

Handy if you can stop the pilot hole just before it breaks thru. ... Fill the pilot with coolant and drill away.
larry

newbury · Jul 9, 2014

SPYDERLK said:
Handy if you can stop the pilot hole just before it breaks thru. ... Fill the pilot with coolant and drill away.
larry

If your oil is thick like honey, or thick and sticky like oil for the chainsaw blade, a small pilot hole may not even drain the oil.

LD1 · Jul 10, 2014

Just had to drill some holes. Clearance for 5/8 bolts, so I drilled 21/32. The steel was 3/8 plate. Pilot hole was a #3 bit. (What I already had chucked). Which is slightly smaller than 1/4.

Wilton drill press set at 215 rpm and a dose of tap magic oil. Each hole took 10-12 seconds. And had all 4 of them drilled I'm a matter of a few minutes.

woodlandfarms · Jul 10, 2014

So clearly I am missing a step with this pilot hole as it took me 10 minutes to get through 1/2". The pilot hole makes this big of difference? Gonna have to test your guys theory on this.

LD1 · Jul 10, 2014

What are you using to drill with? A hand drill certainly won't do it that fast. But if you are using a mag drill or drill press, you shouldn't be over 20-30 seconds for a 3/4" hole through 1/2" with a pilot hole and a good bit.

LD1 · Jul 10, 2014

And I know everyone keeps talking about hole saws, but then in the same breath say you have to go slow and tons of lube.

I just don't see a hole saw drilling as fast a s a good bit. Especially in thick material. Cause a hole saw isn't very efficient at expelling chips, and tend to plug up.

Brad_Blazer · Jul 10, 2014

woodlandfarms said:
So clearly I am missing a step with this pilot hole as it took me 10 minutes to get through 1/2". The pilot hole makes this big of difference? Gonna have to test your guys theory on this.

Drilling a hole much bigger than 1/4" by hand it's hard to keep the bit cutting unless there is a pilot hole. Ideally you produce a continuous chip but if you are not at least producing a steady stream of small chips it's time to regroup. If the bit is rubbing and not cutting it will dull quickly. Spending 10 minutes on a hole will wear out most bits.

On vertical surfaces I like to leave a trail of oil leading upward from the hole. The oil will follow the trail down to the hole for a little while.

downsizingnow48 · Jul 10, 2014

I agree with LD1 about hole saws and also about how fast a hole can be drilled with a twist drill if you have the right pilot hole. The conversation is useful so thanks to woodland for getting it going. This is what works for me (not intended as a statement of "best" practice). Twist drills up to 1/2" with pilot hole about 1/2 the diameter of finished hole. Annular cutters for holes 5/16" to 1 1/16" depending on material thickness (no pilot hole needed). Hole saws only for larger diameters. In all cases I keep the drill bit and hole wet with cutting oil for cooling and removing chips.

woodlandfarms · Jul 10, 2014

My holes are by hand with a Milwaulkee 1/2" Hammer Drill (on drill mode). My drill press was problematic for this large piece. I say 10 minutes as time does not fly when drilling holes. But I know I wasn't 30 seconds.

MinnesotaDaveChalmers · Jul 10, 2014

I agree with the above comments about time, <1 minute per hole after the pilot hole is drilled.
Sharpen as soon as it gets dull or you're just wasting your muscle.
I like to stand on the piece I'm drilling with the side handle against my leg and power it through

The pilot bit has to be at least the same size as the chisel point (that center area) on your big bit. I'm not home or I'd go measure mine and see how big it is.

One tip for hole saw use, get it started so the saw makes a mark, then drill a few holes around the rim on that mark for the chips to escape.
Learned that one about 25 years too late.....

Edit: I hate drilling by hand actually, that's why I have the big Drill Doctor - after a few sharpenings by eye, I'm a little off and it fixes them right up.
Also, when drilling on vehicles laying on the floor, I put the drill on a jack and let it push.
When drilling frames, I hook a pry bar to a chain and use it as a lever to pull the drill into the frame...