Drill Bit Process Question

[waxer]

Ok I just got my new set of Cobalt Drill bits and I need to end up with a 1" hole in some 1x2" bar stock (mild steel)

The question is, what is the best way to drill this?

Should I start small and step up the bits, or just use the 1" bit throughout the whole thing?


Thanks....

[Dan]

I vote you step drill the hole.

[morpheus]

if it were me i'd start with like an 1/8" bit, then step up to 1/4, then 3/8, then 1/2 or 5/8, then 3/4, then 1" ... it's time consuming but with steel that thick that's how I've done it in the past.

it's been my experience that your big drill bits 1/2" and up, will last much longer if you start small and step up instead of just trying to drill with a big bit.

- jack

[waxer]

Gotcha.... sounds pretty easily done.

[Summit Machine]

it's actualy harder on the drill to step drill the hole. If you are looking for a 1" hole I would use the closest drill you have to 1" and finish it with the 1" drill. Be sure to use lots of oil to cool your drills.

[Suburban_Guy]

I used to sneak up on a big hole, but since I bought some good cutting fluid (Tap Magic) I haven't felt the need to ever since.

Harley

[Franz]

In a drill press, 1/4 hole first, then 1" if a perfect hole isn't necessary. If a perfect hole is necessary, 1/4, 15/16, and then 1".

No drill press, make as many steps as you feel comfortable with.

[openboater]

Drill speed is very very important. I just wish I could remember what speed to use.

30 years ago when I was a student at Cornell, the most usefull course I took was 'ag engineering 101', nick named 'arc's and sparks'.

part of that course was proper drill bit sharpening, and drill speed. If you get it right , you make those wonderful long curly-q's coming off the bit. That was what we had to turn in for our grade on that part of the course.

I wish I still had the course book, it was the mose comprehensive book on do-it-yourself i've ever seen.

I've never had an occasion to use a carbon-arc torch to braze since I left that class. Some things 'do' go out of style.

[chip hayden]

if you pilot drill a hole, the pilot drill should be the same diameter as the web thickness of the finish drill[about 1/8" for a non split point 1" drill]. if you go in steps it rips the cutting lips off the drill, and feels like you are going to break your wrist, if you have a decent pistol drill. if you must go in steps to your finish diameter, flatten the cutting lips of the drill to get a chisel edge. this way the drill won't want to screw itself into the piece. you won't get the v shaped spiral chips but, little c shaped curls the width of the drill lands.