3/4 drill

[Teenager with old tools]

If this is in the wrong place I'm sorry but not many forums on tapatalk for this and web browser forums are a pain in the rear on my phone. A friend at school said he needed a hole drilled in steel. 3/4 inch hold in 1/4 inch steel. I have a 3/4 drill bit of unknown quality all it reads is 3/4 hss I have a decent 5/8 bit and good set up to half inch. Never needed above 1/2 but bought the 5/8 and 3/4 in a dollar pile of stuff. Should I drill a pilot hole then 1/2 then 5/8 then 3/4 or right from 1/2 to 3/4 I have a drill press. Thanks


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[Schurkey]

Depends on your equipment.

Ideally, you'd select a pilot drill based on the thickness of the web of the final drill size--3/4" in this case.

One pilot drill hole, then hit it with the 3/4".

Some guys want to sneak-up on the final size, by drilling with progressively larger bits. This creates lots of work, lots of drill-bit changes in the chuck, lots of speed-setting changes on the drill press...and in the end you just wind up ruining a bunch of drill bits by wiping-out the outer edge of the cutting lips. A side-benefit is that the center of the hole wanders all over creation from uneven cutting.

I have on very rare occasions needed a pilot drill to fit the web of the final drill bit--and then a smaller pilot drill to fit the web of the "larger pilot drill". But the principle is the same--pilot drill bits to fit the web of the larger drill bit.

 

[pepi]

3/4 hole, 1/4 thick stock........ hole saw 3/4 in, is the way to go, low speed lots of cutting oil.

Just punched a 7/8in hole in 2 stacked, 1/4 bar pieces.
Was going to drill it but figured out the hole saw was a better option.

Not sure about your drill press, but need the speed low 200 rpm or less. These holes started out at 250, but were reduced to 100 rpm, tool ran nice and cool at both but the 100 speed cut faster.

 

[dr_clyde]

Thru hole? Pilot 1/8"' then take a 3/4" max step drill in a hole shooter and drill the hole.

 

[A_Pmech]

Agree with Dr. Clyde. Use a step drill for that with a battery hand drill.

 

[Farmall450]

Agree with Dr. Clyde. Use a step drill for that with a battery hand drill.

+1. A twist drill will break your wrist if you try a small jump in sizes.

 

[Strouty]

And just so you know step drill bits will work in thick steel as well, as long as you are drilling maximum size of the bit. I have drilled 1" thick plate, had to drill it from both sides, but worked well.

I would also buy the Harbor Freight step drill bits, they get rave reviews and are so inexpensive you can buy more than one.

 

[fnieto]

Step drilling will give you the best results if you only have drill bits.

 

[Packard V8]

Step drilling will give you the best results if you only have drill bits.

Guess I'm the only one here who doesn't like step drills. If they're so wonderful, how come I don't see them in industrial applications?

jack vines

 

[dittle fart around]

Guess I'm the only one here who doesn't like step drills. If they're so wonderful, how come I don't see them in industrial applications?

jack vines

We used them all the time building and modifying switch gear and control panels in high voltage substations. That was mainly on aluminum though.

I would think going through 1" steel plate would burn those babies out?

We didn't get the ones from harbor freight.

 

[sberry]

Just drill it and see how it goes, doubt you want to make a career of 1 hole.

 

[JerryB]

The OP says he has a drill press.

As others suggested above, I would clamp the work to the DP table, drill a small (1/8" to 3/16") pilot hole, then move directly to the 3/4" drill. Assuming mild steel, I would use a slow to moderate speed with lots of cutting fluid. I like Tap Magic, but everyone has their favorite.

 

[Teenager with old tools]

Just drill it and see how it goes, doubt you want to make a career of 1 hole.

No but I don't wanna screw up the hole nor do I want to screw up a bit. Even tho I paid a buck for it and others I don't wanna have to by another one if avoidable.

The OP says he has a drill press.

As others suggested above, I would clamp the work to the DP table, drill a small (1/8" to 3/16") pilot hole, then move directly to the 3/4" drill. Assuming mild steel, I would use a slow to moderate speed with lots of cutting fluid. I like Tap Magic, but everyone has their favorite.

Thanks. I have tap magic around somewhere


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[Leaflessshadetree]

The OP says he has a drill press.

As others suggested above, I would clamp the work to the DP table, drill a small (1/8" to 3/16") pilot hole, then move directly to the 3/4" drill. Assuming mild steel, I would use a slow to moderate speed with lots of cutting fluid. I like Tap Magic, but everyone has their favorite.

This is how I would do it as well.
Step drills and hole saws work OK on thin metal.

 

[FigureItOut]

Get yourself a set of rotabroach cutters, you'll cut a perfect hole in 5 seconds, and be covered nicely for future holes. https://www.amazon.com/gp/aw/d/B008...oach+11090&dpPl=1&dpID=418RiUK3ScL&ref=plSrch

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[md21722]

Rotabroach work good, as do step drills, or as the others said, drill pilot thickness of the web, then go to 3/4". If you try to change sizes repeatedly, I suggest 118 degree as the 135 will just tear themselves and you up when they try to bite. I have snapped Norseman's in half trying to widen a hole. Wear eye protection. The comments about 100-250 RPM are very good too. For best results, the drill press should be 1-2 HP.

 

[PugetDude]

I just drilled a couple of 3/4" holes through 1/4" flat bar in my 30 year old Grizzly drill press. Slowest speed, a little lube (I use chain saw bar oil- it's really sticky) and steady feed pressure.
Used 1/8" pilot, stepped up to 3/8", then 1/2", then 3/4"; No problems.

Probably took as long to type this post than it did to drill the holes.

 

[fnieto]

Guess I'm the only one here who doesn't like step drills. If they're so wonderful, how come I don't see them in industrial applications?

jack vines

I'm not talking about one bit with steps. Step drilling up in size like he did^^^^^

If he had access to annular cutters then I would have recommended using one.
They cut a perfect hole. But to recommend buying one for one hole is impractical.

 

[Lee Celtic]

Had to google Web.. thought I'd share for those too embarrassed to ask..lol

 

[Schurkey]

Had to google Web.. thought I'd share for those too embarrassed to ask..lol

I don't see any representation of "back clearance" in that illustration. That's the angle that the back-side of the cutting lips fall away from the cutting edge.

Too much makes the cutting edge weak, too little generates excess heat to the point of localized melting of the bit.

There's a science to sharpening a drill bit--but it can be done by hand on a decent grinding wheel for any common sizes. (The smaller bits are more difficult than the bigger ones.) The hateful truth is that it's entirely possible to hand-sharpen a drill bit BETTER than low-grade "drill bit sharpener" machines.)

 

[dr_clyde]

Step drills, vari-bit, unibit, whatever you want to call them, are widely used in industry. Most machine shops have a better setup than a drill press and an unknown drill to make holes with though.

They are indispensable for making round holes up to about 3/4" or so in material 1/4" and under, especially in low horsepower and less than rigid apps.