Thread: Will I tear up a Starrett Hole Saw cutting 20 gage stainless? Secrets to the job?

Gents I have about a dozen holes to drill in 16 Gage (0.060) stainless sheet, 4 holes at 2.125 and 7 at 1.375. I was hopping that I might get by with the standard Starrett hole saw (bi metal variable pitch the standard yellow type). This would be done on my Bridgeport with variable speed. I haven't had the opportunity to do much stainless work, what little drilling I have done tends to tear up a drill bit pretty fast.

Are these hole saws useable for stainless? If so, what might the treasured trade secrets, tips, suggestions or words of wisdom to prevent putting an eye out and ruining a perfectly good hole saw that you could share with me.

In advance, thank you, your time and suggestions is greatly appreciated. Cheers.

Very slow speed, coolant, plywood backing and good clamping, for starters.

Larry

Kool Mist works well to keep the cutting zone cool.

Unless your Bridgeport will run at 60rpm or less it's going to burn up the teeth on the 2 1/8"er. As said already, VERY slow, coolant.

Three things come to mind, get your setup as rigid as possible, use lots of coolant and get your speed way down. The coolant flushes the chips out of the cut, preventing binding, which is one of the biggest killers of hole saws. On the box the hole saw came in there should be a chart with a recommended rpm/surface speed. For SS you want to go even slower. And once you start the cut, don't pull out. This is where the coolant flush comes in. Without it you have to pull the saw out to clear the chips and every time you do you take a tiny bit off the cutting edge. As the edge loses its sharpness you get more heat, less cutting and, eventually, bad things happening. Try to keep the tool cutting all the way through without stopping,

My only other recommendation is to use a rotobroach instead of a hole saw. More money to start but if you use the same procedure as above they'll last a lot longer and cut much more accurate holes than a holesaw...

I know on regular steel they last forever, usually they come with a speed chart so follow that and you should be good.

For sheet metal I would recommend their straight pitch ones made for sheet metal, I know my local store sells both.

Gents as always I can count on you fellows for excellent advice and words of wisdom, thank you to each of you for your help. I can get the mill down with the VFD to some pretty slow RPMs. You know I am embarrassed to say this, but I usually pitch those pesky instruction sheets thinking they are all about putting your eye out. But I pulled them out and low and behold they have the cutting speed for Stainless at 1 3/8 and 2 1/8 at 125 RPM and 80 RPM respectively. Following your advice I will:

Slow'r way down
Back it with plywood
Flood it like Noah's ark type flood
Don't pull out no matter what give'r hell

I have always wanted to get my mitts on some rotobroach's this might just be the excuse to get some.

Again, thank you for sharing the experience.

I have one more tidbit to add. The secret to successful hole sawing is to have a chip relief hole drilled in the perimeter. Try it.

1potato--I too have either read or heard that also thank you for the tip, I'll make sure I drop a couple in before the operation. Thanks.

Might try a different saw for this job. I like these: Relton Corporation - Hole Saws

I like Starrets too, but horses for courses.

And I agree with all the previous advice if you stick with what you have--slow, coolant, relief hole.

Originally Posted by 1potatoe

I have one more tidbit to add. The secret to successful hole sawing is to have a chip relief hole drilled in the perimeter. Try it.

What's a "chip relief hole" ? A smaller hole drilled inside the larger hole being cut? Presumably it goes through the material and the edge touches the circumference of the main hole you're making? What happens? chips get dumped in here?

Originally Posted by karavshin

What's a "chip relief hole" ? A smaller hole drilled inside the larger hole being cut? Presumably it goes through the material and the edge touches the circumference of the main hole you're making? What happens? chips get dumped in here?

Yes to all of the above. It breaks up the chips and it helps the saw advance . It works wonders.----

Hammerfest, Why not consider some Greenlee KNOCKOUT PUNCHES, both sizes mentioned are trade sizes for conduit, They make special SLUG-SPLITTERS, FOR STAINLESS, And do a lot better job than a hole-saw.
dave [acme thread]

Acme Thread--great idea, if I had to do a bunch of those that would be the ticket, but for this one off project I might be cheaper with the hole saw. I will however check into what a couple of them might run. It definetly does a much cleaner job. Thanks for the suggestion.

I just used some Greenlee punches at work today, all I can say is I will never use a holesaw again if I don't have to.

If you can clamp the work firmly enough and control the feed tightly enough, a trepanning tool will work just as well if not better than a hole saw for this sort of cut.

All that being said, make sure you spit on it and ease it in there gently!

Hammerfest what kinda tol. on the holes and do you have a plasma cutter

This is one of several reasons to have a VFD on your gearhead (Arboga...Wilton...ETC) drill press. Arboga style if you want 20 rpm turn the control down to 20 % or so. I really like the machine for drilling Glass with a diamond bit just add water.......

Tasmo--I do have a Miller Plasma and it did enter my mind to use it with a form of jig, it would certainly be fast if it weren't for having to hunt down something of close dimension. The tolerance on this project isn't tight what so ever these wholes are for 50 AMP 220V plugs. Just didn't want it looking like a toothless hillbilly cobbed up job.