secret of drilling metal

masraum · 01-08-2006, 02:54 PM

OK, what's the secret of drilling through metal? slow, fast, a certain type of bit? I just bought a 1/4" "metal" bit and tried to drill through a bed frame which I guess is 1/8 mild steel and the bit dulled before I was through the frame.

I realized that I don't have to drill through, but I'd like to be able to in the future if I need to.

jim72911t · 01-08-2006, 02:59 PM

Don't spin the drill too fast. This heats up the cutting edge and dulls the drill bit. A drop or two of oil doesn't hurt either. Also, make sure you are using a high speed steel drill bit (or better.) to be honest most of the drill bits you can buy at hardware stores are crap.

Good Luck!

Jim

Joeaksa · 01-08-2006, 03:08 PM

What Jim said is correct. Most of the drill bits out there these days are terrible.

Spend $100 at a good store and get some bits, keep them out of the hands of the kids and they will last you a lifetime if you take care of them.

JoeA

911pcars · 01-08-2006, 03:21 PM

There's a formula for cutting speed. It depends on the material to be drilled and the drill size. Assuming a sharp drill, the correct cutting speed will result in the material curling off of the drill bit in long strings rather than in small bits. And yes, a cutting fluid is recommended as well.

I can't recall, but a quick search in Google should give you the needed calcs.

A good technique is to drill a small pilot hole before drilling with the final size drill.

Sherwood

BGCarrera32 · 01-08-2006, 03:25 PM

In a nutshell, the larger diameter the bit (which will dictate the length of the cutting edge at the tip) the slower you should spin it and the more feed (or feed pressure) you will need. Say 1000+ rpm with a hand drill pushing very gently for a 1/8" bit down to 100-200 rpm for a 1/2" bit giving it some steady push. Also start your drill hole with a center punch which will prevent the bit from walking when you first start the hole. Even the best bits get wrecked fast if you use them wrong...

Obviously this is all material dependant and drill bit dependent, but you get the idea.

5axis · 01-08-2006, 03:27 PM

There are well established speeds and feeds for drilling all types of metals. These numbers work fine if you can generate enough pressure to meet the feed #'s. That means drilling with at least a drill press in most cases. When you have to use a hand drill, you will have to spin it slow because you can not feed hard/fast enough to cut properly.

The short version: you want to make metal chips not dust.

turbo6bar · 01-08-2006, 03:28 PM

You must consider the metal and diameter of the drill bit.

Point your browser to:
http://its.fvtc.edu/MachShop1/drillpress/cutspeeds.htm

For mild steel (1018), you might want 65 fpm cutting speed. Use the equation to calculate RPM.

RPM = cutting speed x 4 / diameter of drill bit
RPM = 65 x 4 / .25 = 1025 RPM

This work is alot easier on a milling machine, but slow and steady with a regular drill will work well.

widgeon13 · 01-08-2006, 03:33 PM

use a punch to mark where you want to drill. Drill pilot holes with smaller drill bit and work up to the size of the final hole if necessary, lubricate liberally (oil), run drill at low speed and if drilling deep hole back out the drill to remove waste material and if possible use a drill press where feasible. The oil lubricates surfaces but also dissipates heat.

masraum · 01-08-2006, 04:12 PM

Yep, as the bit turned at a fire starting max rpm and the bit dulled to the point that it'd have a hard time getting through butter I thought to myself, "Didn't dad tell me years ago that to drill metal you had to use low rpm?"

So, now you see the problem, thanks all, next time it's slow going.

M.D. Holloway · 01-08-2006, 04:27 PM

Complicated - Send me a PM with your shipping address and I will send you a real cool slide rule thing that is perfect for figuering the right RPM vs Metal alloy as well as a bunch of other real great info. .

island911 · 01-08-2006, 04:29 PM

coolant .. .cutting fluid

techweenie · techweenie's Garage

To generalize: the slowest possible speed is best for most workable metals. Try to produce a continuous 'ribbon' from the drill bit.

Joeaksa · 01-08-2006, 05:33 PM

Quote:

Originally posted by LubeMaster77
Complicated - Send me a PM with your shipping address and I will send you a real cool slide rule thing that is perfect for figuering the right RPM vs Metal alloy as well as a bunch of other real great info. .

Excuse me... "slide rule thing"????? Todays kids do not even know what a slide rule is, even though it took men to the moon and back!

Joe

austin552 · austin552's Garage

How thick, sheet metal or bank vault?

5axis · 01-08-2006, 06:01 PM

Quote:

Originally posted by turbo6bar
You must consider the metal and diameter of the drill bit.

Point your browser to:
http://its.fvtc.edu/MachShop1/drillpress/cutspeeds.htm

For mild steel (1018), you might want 65 fpm cutting speed. Use the equation to calculate RPM.

RPM = cutting speed x 4 / diameter of drill bit
RPM = 65 x 4 / .25 = 1025 RPM

This work is alot easier on a milling machine, but slow and steady with a regular drill will work well.

Next figure a feed so the cutter is cutting and not just rubbing it's way through the steel. Try a nice easy 0.001 per tooth. = .002 per rev = 2.05 inches per min feed. Try to avoid feeding slower than .001 or you are back to rubbing instead of cutting. This is why it is hard to hand drill stuff. You need to really slow down to get a decent chip load.

masraum · 01-08-2006, 06:27 PM

Quote:

Originally posted by Joeaksa
Excuse me... "slide rule thing"????? Todays kids do not even know what a slide rule is, even though it took men to the moon and back!

Joe

I've got a basic pickett and 6 soroban (japanese abacus). I think I can figure it out.

M.D. Holloway · 01-08-2006, 07:05 PM

Steve - I'm confident you can! Our metal working fluid guys made it several years ago. Customers love it - sometimes I think they buy our juice for the cool things we give out! (Actually the juice is good stuff)

jim72911t · 01-08-2006, 09:30 PM

Quote:

Originally posted by techweenie
To generalize: the slowest possible speed is best for most workable metals. Try to produce a continuous 'ribbon' from the drill bit.

Tech, if we followed that advice at work, we'd go out of business!

(I manage a small CNC shop.)

While your advice is probably worth following for somebody using a hand held drill or even a drill press, it doesn't quite work for most machine shop applications using higher speed equipment. Fact is, the chip actually serves a useful function by carrying heat away from the cutting edge of the drill.

In my experience drilling is both a science and an art, neither of which I've come close to mastering in my fifteen years in the field.

Jim

island911 · 01-08-2006, 10:30 PM

Quote:

Originally posted by jim72911t
Tech, if we followed that advice at work, we'd go out of business! . . .

Well, that may be . . .BUT, at least techwee would have another reason to blame Bush.

masraum · 01-09-2006, 06:20 AM

What's the best lubricant and how much would need to be used?