Cutting hole in mild steel

[Shaun @ Tru6]

I have to put new rear wheel bearings in the BMW. Have a SIR Tools set to do 911s, quick and easy job, but needed a proper sized disc for the slightly smaller BMW bearing. Got a carbide Milwaukee hole saw to cut one out of some 3/8 mild steel plate. Low speed on the drill press with cutting oil, it got down a little over 1/8 and it's done.

Does that seem right? Milwaukee CS is closed for the weekend. Might have to cut the rest of it out roughly with a jig saw or grinder disc and put it on the lathe.

[pwd72s]

Is there a laser cutting service in Cambridge?

[hcoles]

Can you use the hole saw instead of the piece you were trying to cut out?

[Shaun @ Tru6]

Originally Posted by pwd72s

Is there a laser cutting service in Cambridge?

it would have to be waterjet cut and then very expensive

Originally Posted by hcoles

Can you use the hole saw instead of the piece you were trying to cut out?

Yes and no. The 3 1/8 inner is perfect. The outer would be too big. A 3" might work or 2 7/8.

This was supposed to be both low cost and fun. Now it just sucks. I could have bought a kit on Amazon for $50 but I do my best to not buy Chinese and was supposed to be fun.

[john70t]

Big teeth don't usually work on harder material even if it says 'for steel'. Only the contact tips are doing any work.

Is there a box store or Grainger nearby with small or a smooth diamond band?
Go through a stack of 'em but get it done.

Use a mix of sand/oil or some kind of abrasive?

[Zeke]

Carbide-mild steel-cutting oil? That should have worked.

But slow for this is really slow. And lifting out of the cut every few seconds for just a second or 2.

Believe it or not, fewer teeth would have been better. Carbide likes a good bite, not just skimming along. You may have done better by really bearing down on the DP if it's got the beans.

Another thing that might have happened is that the work got hardened. Try your cutter in a fresh cut. If it works, don't let the process get hot. Keep jumping in and out of the cut.

Worst case is that you can make a good pattern for a jigsaw to follow. And if you have a metal lathe and a way to mount the work, rough it out with a disc grinder and finish with the lathe. You don't want it too jagged or you'll have trouble.

If you can find some thick wall pipe you may be able to cut sections and use cross plates. You weld, right? I mean fundamental stick or something.

Edit: I see while I was typing that you could have bought a kit for 50. I'll bet the bit was all of that. And I wouldn't worry about it being from china. The bit probably was.

[john walker's workshop]

Cut it out close as possible with a band saw and finish it in the lathe.

[Shaun @ Tru6]

Originally Posted by john walker's workshop

Cut it out close as possible with a band saw and finish it in the lathe.

That's what I'm going to do.

[Shaun @ Tru6]

I thought it would work because it is supposed to cut through stainless steel which is a heck of lot harder than this plastic steel I have. I would have been happy if one time use to be honest. But 1/8" is not right.

[908/930]

How slow can your drill press go, gear head or only belts? Likely spinning too fast I would run that at about 60-80rpm and lots of pressure for a couple seconds, as Zeke mentioned there is a chance you work hardened the metal but really should not have if it is only mild steel, but mild steel is a loose term. If you still have sharp teeth on the hole saw try cutting from the other side of the plate.

[Scott Douglas]

You have a lathe available and you're doing it this way (ref to pic)?

A lathe is always more fun than a drill press, IMHO.

[Zeke]

^^^Yeah, it's not likely the teeth are bad. Not at only an eighth. Lots of closely spaced teeth are for thin sheet. Not for plate. 4 teeth would have done that job.

Originally Posted by Scott Douglas

You have a lathe available and you're doing it this way (ref to pic)?

A lathe is always more fun than a drill press, IMHO.

Well, he still has to have something that resembles a round. He could put a square in the lathe and cut it from the face like parting. Still, mounting a flat round in a lathe to work the outer edge is a small challenge. I'll leave it at that, drive dogs and all.

[Scott Douglas]

He's got a center hole already, put it on a spud to drive it.

[Shaun @ Tru6]

This was supremely satisfying. I love grinders and cutting discs. Lathe tomorrow.

[Zeke]

Originally Posted by Scott Douglas

He's got a center hole already, put it on a spud to drive it.

The mechanical force is pretty high as you get further out from that hole.

I'm not sure what a 'spud' is. I looked it up and I didn't see anything specific.

[Shaun @ Tru6]

Originally Posted by 908/930

How slow can your drill press go, gear head or only belts? Likely spinning too fast I would run that at about 60-80rpm and lots of pressure for a couple seconds, as Zeke mentioned there is a chance you work hardened the metal but really should not have if it is only mild steel, but mild steel is a loose term. If you still have sharp teeth on the hole saw try cutting from the other side of the plate.

So it's my fault then. Drill press can do down to 210rpm but it was at 400.

[Zeke]

RPM is not as much of a factor as cutting speed. At that diameter the math can be worked out as to what the cutting speed is but I can say that's too high. Way too high. 400 is for more like a 1" drill twist bit. Real small bits are used in the low thousands of RPM.

[908/930]

Yup, operator error, lol. Quite the pain to make a 3" disk, a CNC mill would have been nice to have. Are you just going to face a piece of bar stock on your lathe and hold the disk with the live centre to turn it? Or do you happen to have soft jaws?

[Shaun @ Tru6]

Live and learn, I had no idea you'd have to go that low but it's great to know for the future.

[Shaun @ Tru6]

I will have to look at packaging at HD but I wonder if these hole saws have a speed table for materials. That would certainly be helpful.