View Full Version : Drilling large hole in steel

Kurt Loup
06-27-2008, 11:26 AM
I need to drill 4 holes larger than 1" in 1/8" thick, 1 1/2" x 3" steel tubing. I have twist drills up to 1/2". If I pre drill with the 1/2" drill, will a step drill bit be appropriate to enlarge the hole to over 1"? The guy at the store insisted that it would drill steel, but I was unsure as I thought they were for drilling sheet metal. If a step drill is not appropriate, what do you recommend? Thanks.


06-27-2008, 11:33 AM
Hole saw, Super drill, silver and deming twist drill...
How much over 1" and at what tolerance?

Quetico Bob
06-27-2008, 11:33 AM
I have very good luck with bi-metal holes saws mounted in the drill press at low rpm. I find using coolant from a squeeze bottle helps that much more.
Cheers, Bob

06-27-2008, 11:35 AM
We use step drills every day in our shop to drill 10 Ga, (.1345) hot rolled steel sheet, works great. We also use hole saws for larger (1.5"-6") holes. I use them mainly for clearance type hole and typically have very large tolerances (+- 1/16"), so that may be an issue for you but, for "just a hole" they work just fine.

06-27-2008, 11:39 AM
"sheet metal" can be steel too;)

1/8" is just thick sheet and that tubing was likely made from sheet rolled and then seam welded.

I too think you will find the best luck with a hole saw. They seem to deal better with thin material than most twist drills. Its really then a trepanning operation rather than drilling operation (except I suppose for the pilot drill in the center of the hole saw).


Kurt Loup
06-27-2008, 11:50 AM
Thanks for the responses. It doesn't need to be of any specific tolerance. I am installing a Bakflip hard cover on the bed of my truck today. I have a Trac Rac rack that mounts to the lip of the bed of my truck that I use to carry my canoes and kayaks. Once the cover is installed, I will not be able to mount my rack to the rails. I plan to mount the steel tubing to the rails of the bed using threaded inserts I added to the stake holes. The rack will then be mounted to the steel tubing. The holes are for clearance for the heads of the bolts that will mount the steel to the stake holes. When the rack is mounted to the steel, the foot of the rack will cover the holes preventing removal of the bolts and theft. The hole will need to be large enough to pass a 3/8" washer through. Kind of tough to describe the project.


06-27-2008, 02:00 PM
cross drilling a tube is different than sheet metal, I'd be thinking a drill or even step drill could easily grab on the big interrupted cut and that a hole saw or even boring bar would be the way to go. In the first case some teeth are always in contact and in the second, the feed is controlled.

what hole saws do you guys us for this sort of app? I've got some Starrett ones that I’ve used and while they work they do bit of a miserable job - much better suited to softwood studs than metal. They are just very crudely made with the weld joining the rolled blade ends being rough and anything but precise. I hear using them for metal so frequently that I’m convinced I’m using the wrong style of hole saw

06-27-2008, 03:39 PM
This hole saw works pretty good.


06-27-2008, 03:46 PM
I would punch the sheet metal. My brothers shop would charge 50 cents a hole in 1/8" plate and it takes 2 seconds or less per hole.

Kurt Loup
06-27-2008, 09:36 PM
A Rigid bimetal hole saw purchased from Home Depot did the trick, but it was bogging down my 3/4 hp drill press. I had to go really slow.


06-28-2008, 11:38 AM
I would punch the sheet metal. My brothers shop would charge 50 cents a hole in 1/8" plate and it takes 2 seconds or less per hole.

In square tube?

06-29-2008, 05:35 AM
Have a look at the super drill. www.practool.com

06-29-2008, 04:35 PM
hougens sheet metal cutter cut sheet like butter:


06-29-2008, 04:36 PM
i hate cutting holes in steel with holesaws. i build bicycle frames, so it's a very common practice to use cheap bimetal holesaws on chromoly tubing to miter tube junctions.

talk about a pain in the butt seeing that the teeth on the holesaw last for about three cuts, then the damn thing basically uses friction to erode the material away if you keep trying after that...

making/buying some arbors like these are a must if you do lots of work with holesaws:


i remember there's diamond grit holesaws out there too, but they were damn pricey iirc...

Quetico Bob
06-29-2008, 05:52 PM
Quote “
i hate cutting holes in steel with holesaws. i build bicycle frames, so it's a very common practice to use cheap bimetal holesaws on chromoly tubing to miter tube junctions. “Quote

Wonder if Chrome Moly might be outside the design envelope for a bi-metal hole saw.
I can’t count the number of holes I bored in plate from 1/8 to ½’ thick with my starret set but it’s always CR or HR. They seem to be like the energizer bunny, they just keep going and going.

Cheers, Bob

Lew Hartswick
06-29-2008, 06:50 PM
In square tube?

That always give me a chuckle. Answers that don't have anything to do with the original
question. :-)

06-29-2008, 09:31 PM
I regularly use the step drills in material larger than the 1/8" step that they allow for. I find that they drill really really nice. The shallow relief angles do not "grab" like a silver and deming will.

I personally HATE holesaws and only use them in a pinch.

As for the method of notching tubing, I suggest you look for the post where someone described how to notch tubing with a cutoff saw....MUCH MUCH easier. Unless you need a really close tolerance.

06-30-2008, 09:58 AM
I've cut 30mm holes in 8mm incolloy plate with hole saws.
Sandvik saws with a squirt of tap-magic, lots of pressure.
Chrome alloys work harden. Keep em cutting.
If you're having trouble with hole-saws, buy better tooling.
I'm just using a POS chiwanese floor drill.

06-30-2008, 10:20 AM
There are two problems with holesaws that have to bee understood....

1. They are not self clearing. Leave the swarf in the bottom of the groove and they will rub it around in circles just making heat and holding the teeth up off the bottom.

2. They have no self feeding characteristics and as such you have to provide all the down force. As someone else pointed out, you can ruin one in no time running the teeth around in a circle rubbing against the bottom while not removing metal. Cutting fluid is something I would consider for anything more than paper thin.

That "super drill" seems like just a boring bar with a pilot. I think a guy could make one, but it might be hard to harden it to the "internationally recognized hardness measure" of Rockwell 60 (as though Rockwell 50 or 65 is not internationally recognized) :D :

"Because the cutters are made from 8% cobalt and the SUPER Drill body is hardened to internationally recognised hardness measure, 60 Rockwell, the SUPER Drill and its cutters is built strong to tackle your toughest drilling."


06-30-2008, 11:43 AM
On holes saws.. They work well if lubricated and used in a drill press. Typically I use a garden spray mister bottle set on stream and a soluble oil cutting emulsion. To eliminate chip loading you can peck drill or drill a tangetial chip unloading hole. I have Greenlee, Morse, and exchange-a-blade bimetal holesaws I've used on 3/16" square tubing without noticeable wear after 6 or 7 holes.

As for the Practool Superdrill - it is little more than a sophisicated boring bar.. 1/2" pilot section with a self feeding grind on the cutter bit that cuts a hint more on the tip than the rest to cut a tapered washer at the base of the cut to prevent catching. Cuts amazingly well with a splash of soluble cutting oil emulsion. Recommended for drill press use only.

No affiliation blah, blah, blah, just another $.02 cdn

06-30-2008, 11:49 AM
Also helps, blow off swarf with air while you "peck" the cut

06-30-2008, 01:06 PM
yeah, i always peck drill with the holesaws and use cutting fluid. i probably should just invest in one of the abrasive grit saw kits.

we actually use an angle grinder to miter sandrail chassis tubing at work. we have some software called bend-tech that helps calculate all the bend parameters and will print out a template for mitering tubing that you can cut out and tape around the tube, then you have a perfect indication of how to fit it up.

on the bicycle stuff, some of the tubing is down to .025" wall, so fitup is critical. i draw my frames in solidworks, then cut the tubes on a milling machine. both ends of most tubes get mitered, but it's pretty easy to eyeball the length using a big steel scale. if you're off by a bit on the length, you can fudge the fit by moving the tube up/down to hit its mating tube, which is almost always at an angle.

if you push your luck with any gaps, though, it's very easy to blow a huge hole in the tubing...

the .025" wall tubing is a special cycle-specific niobium alloy similar to chromoly. the stuff is ultra pure and designed to be corrosion resistant, so it welds like a dream. everything else is high end 4130 that i get from an aircraft supply company and always get certs on, so welding frames is really, really nice.

the tubes are http://www.columbustubi.com/eng/4_4_6.htm . A.L. colombo, the parent company, also makes the steel that ferrari uses for its chassis...