Big drill bits

[ArlyA]

I agree. Cobalt is a good HSS product and I buy tools made from it. In particular countersink tools.

A quality cobalt bit, slow speed, and oil, will drill through most anything.

 

[denchen]

Large drill bit, verses rotary cutter. I think it may depend on how many holes you have to drill. In the factory I used to work in, it might have been 200, two and a quarter inch holes in plate, half inch thick, every day. Many other holes would also have to have been drilled. A small pilot was drilled, about a quarter of an inch then the 2 1/4 went straight through, slow speed, power feed, alkaloid oil/ water mix to cool. The oil water mix looks like milk. This was all done on a big radial drill. No way would it be possible to hold a hand drill with this amount of torque. Now if I wanted to drill the same size hole at home, then a rotary cutter would do the job, but a lot slower, with a good power drill. The drill bits we used were normal good quality bits, nothing fancy like cobalt, and were sharpened when I got around to it about once every 3 - 4 weeks or if someone done something daft and one got chipped. I don`t think a rotary cutter would last long in our working environment. The other way of making holes in our factory was simply to punch them out cold. The square holes in the hard tips of power harrows for the bolts, were made this way

 

[Oldpath05]

Maybe a good quality drilling lube will make big drill bits last longer, something like this>> Anchorlube G-771, water/soap based metalworking lubricant

 

[radios1]

Large drill bit, verses rotary cutter. I think it may depend on how many holes you have to drill. In the factory I used to work in, it might have been 200, two and a quarter inch holes in plate, half inch thick, every day. Many other holes would also have to have been drilled. A small pilot was drilled, about a quarter of an inch then the 2 1/4 went straight through, slow speed, power feed, alkaloid oil/ water mix to cool. The oil water mix looks like milk. This was all done on a big radial drill. No way would it be possible to hold a hand drill with this amount of torque. Now if I wanted to drill the same size hole at home, then a rotary cutter would do the job, but a lot slower, with a good power drill. The drill bits we used were normal good quality bits, nothing fancy like cobalt, and were sharpened when I got around to it about once every 3 - 4 weeks or if someone done something daft and one got chipped. I don`t think a rotary cutter would last long in our working environment. The other way of making holes in our factory was simply to punch them out cold. The square holes in the hard tips of power harrows for the bolts, were made this way

for production, this is used. https://www.mscdirect.com/product/details/88425228

 

[BukitCase]

Wow, at $400 per size (not including the machine to use it) I'm kinda glad I got my mag drill when overtime was still an option - I went with a larger drill so I could drill larger holes easier, have about $2200 TOTAL (including 3 vises, xy table, etc) invested INCLUDING cutters from 7/16" up to 1-1/2" (the size of all the pins in my backhoe except 1) - most cutters up to 1" are $30-40 (the cost of a decent twist drill that size)

These days, if you don't need much bigger than 1" holes there are drills that'll do it for around $400.

Here's my setup

https://www.tractorbynet.com/forums...-table-build-6.html?highlight=mag+drill+table

I've added a few more cutters since this pic - - need to come up with a bigger "index" - if you only buy cutters as needed, the "onesie-twosies" aren't as painful as getting every size would be...

I do quite a bit of stuff using 1/4" wall square tube; I have over 100 holes on some of my bits, they're all still as sharp as new.

The part that ALWAYS makes me smile - a 5/8" hole in 1/4" steel takes me 20 SECONDS - NOT a misprint; no pilot hole, just do it. Anything I can't do on the table I can usually find a way to clamp a piece of steel to it (if it's not big enough by itself to just hold the drill to it and turn on the magnets)

For stuff that even the mag drill can't get to, the Blair rotobroach kit can drill down to 1/4" holes with a HAND HELD drill. (as long as you don't get TOO wobbly holding it; they CAN be broken, DAMHIKT )

I know, not for everybody; but worth considering if you see a lot of bigger holes in your future... Steve

 

[TractorGuy]

I like hole saws too, but the tolerence usually suffers.

I consider much of my work butcher engineering, but if the final result is pretty good, who cares how you got there?

The difference in drillbit quality from one make to another cannot be over stated. That pretty much applies to any cutting tool.

I've got an old 5/8 bit that cuts the old Chrysler symbol. It's always been a mystery how a round bit does that.

 

[Industrial Toys]

I sold my Van Dugen (sp?) mag drill to a friend because his didn't have variable speed and mine did. I sold it because I could not afford or justify the angular cutters.

Now, for impressive holes, I go to my other friend who works with a 40 (or so) foot long tubing laser!

 

[k0ua]

I tend to use hole saws for anything 3/4" and above.

Are you drilling free handed or with a press?

Same here. Go slow, lube, clear chips. Do't burn up the holesaw. It is a lot easier on the drill too.

 

[Industrial Toys]

I unfortunately destroyed a 6" Millwalkee hold saw on a stainless electrical cabinet. Even used SS cutting fluid and went slow!

 

[k0ua]

By hand makes my wrists hurt. I'm always concerned with the drill hanging and making pretzels out of wrists. Size like that really needs to be done with a drill press if possible, which it isn't always.

I have some experience with a huge 5/8 slow speed drill. You know the good old metal cased kind built back about when I was born, and a 5/8'' bit in it. So drilling a 3 inch steel pipe. and when it broke thru on the back side, it just about broke both wrists before I could get off of the trigger. It started to wrap up my hands, cord and me. Wasn't fun.