cutting steel plate with circular saw?

I cut up a big old refrigerator with a circular saw and a abrasive blade. I started using a metal cutting blade, which quickly dulled.

The process was highly unpleasant. (much of unpleasantness was related to how the refrigerator was built, not to cutting metal as such).

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There are special saws made for that purpose - available from places like Princess Auto and Northern Tool.

For 50 feet, just buy an abrasive blade (not a "cold saw" or anything with teeth) and go make sparks with the saw you have (or a real cheap one picked up at a yard sale, if you have a "good" wood cutting skilsaw and want to be nice to it). One blade will probably do it unless you force it.

I would not buy a metal blade. I would buy a quantity of abrasive blades, use them, and return the ones that were not used. I doubt that one would be enough to cut 50 feet of material.

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Hi, Ben. You can do this nowadays. You can either get your hands on a saw designed to do it, or you can use a worm drive saw. It's my understanding that a regular Skilsaw isn't up to the job. I have a Skil Model 77 worm drive saw with a blade made by Matsushita, and I used it to make several cuts in 1/4" steel plate. The best way to make your cuts is with a large shear but if you can't get some time on one of those then the new saw blade technology is the next best way to go.

You have to wear ear protection, full face mask, and wear sturdy clothing that covers you everywhere you don't want burned. You can cut freehand but I clamp a straightedge and use that to guide my cut. My cuts came out really straight and clean as a whistle.

My saw blade came with insert literature that says you should never allow a tooth to come fully out of the back side of the cut. Ernie says he never heard of such a thing and uses his to cut tubing. I was cutting flat plate and did what the blade literature said to do and had no problems.

You should easily get 50' from one blade. Don't even think about an abrasive blade. Google this group for "ernie tenryu" and you should get some relevant hits.

Grant

You will be much happier with a metal cutting blade and a worm drive saw than the abrasive blades. I have cut 1/4 inch steel both ways.

I bought an old worm drive saw at a garage sale, and then bought a good metal cutting blade meant for steel up to 1/4 inch thick. Works amazingly well.

The length of the cut should be a non-issue. Don't force the saw, no matter what blade you have.

Richard

Grant Erw>

I bought a rotary saw at harbor Freight (about $60) that is made for cutting metal. It works, but I haven't used it enough to judge blade life. The main drawback I found was that you can't see the blade edge well enough to follow a line--it would be good to clamp on a straightedge.

--Do yourself a huge favor and find a friend with a plasma torch. It'll save you tons of time and there will be less chance of the stress-induced bending you'd get from using a saw.

Ed, with all due respect I'm guessing you have never used one of these saws. There is no comparison to the edge you get between a sawn edge and a plasma cut one. Any metal can bend of course, and if it's light gage sheet it would certainly bend under the weight of a worm-drive saw, but it's easy to support a workpiece on 2x4s separated just far enough to admit the saw blade.

Grant

The saw blade can do a good job, but it's an expensive blade and will be a pretty slow cut. A good plasma cutter, which you are also more likely to find someone with, will tear through the 50' of cut in 1/8" and 1/4" material as fast as you can move the torch and leave an edge just about as clean as the saw, while using about $0.25 worth of the torch consumables.

Pete C.

Pete, as I am going to pick up a plasma cutter tonight (for my own use, not resale), would you have any suggestions for making guides for cutting to make neat straight or properly curved cuts. I suppose that one can start with a simple aluminum straightedge, but have you tried any circle cutting attachments, etc?

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First, don't try using an abrasive blade with a circular saw WITH A PLASTIC HOUSING. [You'll melt the poor thing.]

Second, abrasive blades are cheaper than the slotted-type metal blades and do a better job. [BTDT, still have what's left of the slotted blade.]

If you have a circular saw with a steel housing, an adequate guide & clamps, and a couple of abrasive blades then you're ready to begin.

BTW, what size are these sheets?

You can make templates out of most anything, 1/8" masonite / hardboard is probably the cheapest and easiest. For thin metal like 1/4" and down you're moving so fast that you won't even burn the template.

Someone a while back posted a pic of their home built circle guide for a plasma cutter either here or in s.e.j.w. It doesn't need to be fancy, nothing more than a piece of rod welded to a collar that will fit the plasma torch nozzle, and a small mounting magnet with a pivot point attached and a clamp for the rod.

Since there is no cutting force with a plasma cutter, you can guide it with nearly anything. In a pinch even a piece of 12ga copper wire stripped from scrap romex will give you a functional circle guide.

Pete C.

Igor, I've now made a couple of plasma cutter circle cutters and haven't got a good one yet. I machined one awhile ago from an old brass nut but that plasma cutter has a hot tip (apparently) because enough current flowed through the central bearing to melt it. Back to the drawing board.

What I do right now is to use pieces of scrap plywood in 1/4" or 3/8" thickness (depending on your torch). For cutting an external guide (the kind I prefer) I start by quickly cutting a hole with a small hole saw. Then I figure the radius of the circle I want, including the critical distance from the edge of the guide to the cut edge (this distance you have to determine from experiment, although you can get a pretty close approximation by measuring from the OD of your torch tip to the outer edge of the central air hole) and set a compass to that radius. Then I set the compass drawing point on the edge of the hole I just sawed out and prick punch the circle center with the other end. (The sawn hole is tangent internally to the hole I'm about to draw.) Then I draw out the circle and then cut it out with a jigsaw (which some people call a saber saw depending on geography) and sand it smooth using a drum sander in the lathe.

Then I rip a rough square around this hole and write the designed hole dimension on the plywood circle template. I use squeeze clamps to locate the template and quickly rip out holes with the plasma cutter. It takes about 50 times as long to make the circle templates as it does to cut the metal.

Grant

Ignoramus3975 wrote:

Ben, This is not the best tool for this job. Find someone or rent a plasma cutter. You will be done in minutes whereas with the method you propose will be slow, dirty, noisy, go thru several blades and possibly destroy the saw.

Bob

circular saws are for woodworking, use either a metal bandsaw (Do-All or Dake) or a plasma cutter.

Tony

Here's one I made. Quick 'n dirty, but it works.

A friend of mine has a metal working wife. He got to buy a plasma machine for her (and gets to use it himself...) She tried tracing around a figure she had cut from 3/4" pine. The pine didn't see the heat. The tip centers inside of the outside barrel that isolates part of the torch electrically.

Martin

Martin H. Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net TSRA, Life; NRA LOH & Endowment Member, Golden Eagle, Patriot"s Medal. NRA Second Amendment Task Force Charter Founder IHMSA and NRA Metallic Silhouette maker & member.

Pete C. wrote: