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Drill bits

Mastiff

Mastiff

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I'm trying to drill some 1/2" holes in a steel bumper, through 1/4" plate. I've drilled holes through the K5 frame numerous times, but this steel is harder and thicker. I have some decent seeming dewault bits, but I'm making practically no progress. I drilled a 1/4" pilot hole through and that went okay, but the 1/2" is too painfully slow. Is there some more expensive bit I can get that will make this less painful, or is this just how it is sometimes? Or should I walk my way up through the sizes instead of trying to do it in two steps? I have to drill 6 holes and don't want it to take 30 minutes per hole!
 
Id say you're half inch is probably shot. Chasing it with a 3/8ths first should help but 1/4in thick is not much, sounds like the bit has seen better days.



As for something better, sure you could buy a $50 carbide drill bit :D

We bought a 3/8ths at work for a production 316L stainless piece and that drill bit is insanely sharp!
 
For future reference I use a smaller bit for pilot, like 1/8", cobalt tipped, few bucks from the local Ace. Once the pilot is done the others seem to go easier.

Anyway, yeah, step up *several* times -- you might even get away with the Harbor Freight titanum-coated ones or one of their cheap step bits. It's a pain to switch bits, I know, but maybe you can hit each of your six holes with one size, then switch sizes and go around again.

-- A
 
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If your drilling diamond plate or steel equally hard,a carbide tipped masonary bit drills that faster than typical high speed bits...
Cobalt or titanium ones work well too...

When you re-sharpen a bit,try to keep the point "flat" ,if you make it too cone shaped it'll drill slow and heat up and dull faster..

I usually have to stop and re-sharpen my bigger bits at least once per hole on tough hardened steel..mine are just old "good" drill bits I bought used..nothing fancy,just normal high speed steel..worst bits I ever bought were some real cheap china ones I bought mostly to have the case they came in--they were black steel like an impact socket,and they'll just glow red and fold in half when you apply too much pressure when drilling steel with them..they aren't much better in wood either,especially pallets made of oak..

When I need a big hole like a 3/4" in a thick steel piece,I use a carbide countersink I found at a flea market ,that has 3 flutes--the thing drills holes faster than a drill,despite being intended to just countersink previously drilled holes..I bored six 3/4" holes in a hunk of 1/2" thick steel for the mounting pad for a small crane on my flatbed with that thing in less than 10 minutes,with my crappy "Companion" drill press that only has a 1/4 HP motor on it..
 
I just drilled 4 1" holes through plate steel with a hand drill with HF cheapy drills.

COME AT ME BRO!


OK, I did actually BEND the 1" drill and broke the 3/4" and had to go to my good drills on the last hole (which I was trying to avoid using in a hand drill)

Just step up 1/8" increments and you will be fine.
 
Thanks for the help. I'll try stepping up in smaller increments, and maybe look into carbide bits if I get too impatient.
 
First question. Are they split point drills? If not toss them and get yourself a set of cobalt split point drills. Your life will be easier.
 
Carbide in a hand drill will last about 1 minute.
Get cobalt, and learn to sharpen them. Money saved with almost no effort.
 
Best drill bits i've ever used were 135* split point Cobalt (Dormer brand = Precision Twist).
 
I like precision twist as they are readily available just about anywhere. But my first choice is Guhring cobalt drills.
 
Well, I got two holes done fairly easily by stepping up in 1/8" increments. The first and last hole are the worst. I think going to a 7/16" in between 3/8 and 1/2 might help. My 1/2" is super dull now, so I'm off to get another (or maybe a sharpener).

Is there a trick or technique to keeping the bit from grabbing when it punches through? I bashed my hands twice when the bit snagged and twisted the whole drill around. Last year I was up under the wheel well drilling and clocked myself in the face when the drill swung around. :doah::whistle: And once the hole is shaped like the bit, the only ways I've figured out of it is to turn the drill speed up, or come from the back side, if possible.
 
Mastiff said:
Is there a trick or technique to keeping the bit from grabbing when it punches through? I bashed my hands twice when the bit snagged and twisted the whole drill around. Last year I was up under the wheel well drilling and clocked myself in the face when the drill swung around. :doah::whistle: And once the hole is shaped like the bit, the only ways I've figured out of it is to turn the drill speed up, or come from the back side, if possible.
Click to expand...

Slow speed (variable speed drill) and some kind of lube. I'm partial to Rapid Tap; it's waxier than just a cutting oil and I find sticks better.

As for un-egging a hole, a Dremel with a good burr (you can get carbide burrs in the 1/8" shank), or maybe a stepless bit.

-- A
 
To stop the drill from catching, you need to feel the point at which its about to brake through. Keep you rpm the same but back way off the pressure.

What happens is the last little bit of material bends rather than cuts away, gets caught in the flutes and grabs the bit. You need to stop it from bending and actually cut it away, since its so thin, the only way to do that is ease up on the pressure.
 
cybrfire said:
To stop the drill from catching, you need to feel the point at which its about to brake through. Keep you rpm the same but back way off the pressure.

What happens is the last little bit of material bends rather than cuts away, gets caught in the flutes and grabs the bit. You need to stop it from bending and actually cut it away, since its so thin, the only way to do that is ease up on the pressure.
Click to expand...

Makes sense. Seems like I'm always using a dull bit, so I'm leaning in on it pretty hard. :rolleyes: I bought a cobalt bit, Ridgid brand from Home Depot. Haven't tried it yet, but hopefully it'll help.
 
That Ridgid "cold fire" bit turned out to be awesome. It went right through. The only thing is it's grabby as anything. I'm totally traumatized and paranoid now about how a grabby bit and powerful drill can smash fingers, etc. When that thing grabbed, it could roll the whole bumper over (sitting on sawhorses). If you are holding the drill a certain way, the rotation can force your finger further into the trigger. I don't really have a solution. I tried going really slow at the end, which helps some, but even when I was not near the end, just barely moving off square could get that thing to grab.

Anyway, I recommend those bits. I'd love to have a whole set at some point, but the 1/2" was $20 alone.
 
cybrfire said:
To stop the drill from catching, you need to feel the point at which its about to brake through. Keep you rpm the same but back way off the pressure.

What happens is the last little bit of material bends rather than cuts away, gets caught in the flutes and grabs the bit. You need to stop it from bending and actually cut it away, since its so thin, the only way to do that is ease up on the pressure.
Click to expand...

Do what he said. That's the best solution. But also keep your bits sharp and clamp something (I use plywood) to the back of your part. It helps cut down on the folding that causes the grabbing.
 
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