In another post, a reader asked why a wood-cutting circular saw cannot be used on metal. Shown above is a metal-cutting circular saw, Milwaukee’s new M18 Fuel model.
In his comment, Ryan asked:
I’m new to all this and recently purchased a Dewalt 60V DCS575. Just wondering why you are not supposed to cut metal with this saw?
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I’ve heard a number of good-sounding possible reasons over the years, many of which make sense. For example, someone might say that the guard isn’t designed to protect users from hot metal sparks and chips, or that the shoe isn’t optimized for use on metal materials, or that the internal components aren’t properly protected from metal chips or dust.
While all of these things could be true, we also have to consider cutting speeds. Wood-cutting circular saws work a lot faster than metal-cutting saws.
Let’s look at 2 saws – Milwaukee’s new M18 Fuel brushless metal-cutting circular saw, and their full-sized M18 Fuel brushless wood-cutting circular saw.
M18 Metal-Cutting Saw: 2782
M18 Wood-Cutting Saw: 2731
The metal-cutting saw blade has a 5-3/8″ to 5-7/8″ blade size and spins at 3,900 RPM. Let’s consider the 5-3/8″ blade size for the purpose of this discussion.
A 5-3/8″ blade has a circumference of 16.9″. Given a rotational speed of 3,900 RPM, the linear speed will be comparable to 65,910 inches per minute, or 91.5 feet per second.
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The wood-cutting circular saw has a 7-1/4″ blade size, spinning at 5,000 RPM.
A 7-1/4″ blade has a circumference of 22.8″. Given a rotational speed of 5,000 RPM, the linear speed will be comparable to 114,000 inches per minute, or 158 feet per second.
91.5 feet per second for the metal-cutting saw and 158 feet per second for the wood-cutting saw is a very big difference.
I know a lot of users use wood-cutting circular saws for cutting light duty metal with the right blade.
But when it comes to cutting a lot of the types of materials you would use a metal-cutting circular saw on, such as angle iron, that wood-cutting circular saw blade is going to be spinning way too fast and might not have the torque needed for fast or safe performance.
And all that is ignoring potential safety concerns in using a tool designed for cutting wood to cut metal.
Notice, for example, that a wood-cutting circular saw often has a dust ejection port that channels sawdust out the side. Metal-cutting saws do not. I can’t seem to find a good answer, at least not quickly, but I’d guess that OSHA regulations would disqualify such wood-cutting circular saws for use on metal materials.
Are there any other reasons why one shouldn’t use a wood circular saw in place of one designed for cutting metal?
fred
With cutting of some metals – a too high cutting speed can result in chips fusing and collecting in the gullets of the blade. Of course as always with cutting metals or wood, one needs to attend to both blade speed and feed rate to get the best cut. Maybe folks get away with cutting things like aluminum because it can be cut at much higher speed than steel – where a too-high speed can result in blade damage like throwing teeth.
Jim Felt
Both my colleagues and our vendor carpenters always use regular chop saws for aluminum cutting. With the right blade and the right cutting lube sticks. Never once have had a problem.
That said we want true square cuts and would never use a free hand saw for our aluminum projects.
Kindorf steel on the other hand we use whatever’s handy. But never a chopsaw. True squareness isn’t nearly as important. Just the occasional cutting oil. And a file for cleanup (if they see me kinda watching).
Stuart
That’s a little different. A miter saw with non-ferrous blade to cut aluminum is one thing. Using a handheld circular saw to cut through steel channels, threaded rod, or pipes is another.
Blythe M
Cutting metal with carbide requires specific speed and torque. However, you can buy abrasive wheels designed for circular saws that work fairly well and are designed for the higher rpm. You won’t get the precision necessarily, will lose depth of cut over time, and will throw sparks. But for the casual user who wants the added versatility they are a good choice over buying a specialized tool they may not need much
Bob
What about dropping in a 5 3/8″ blade into a wood saw. Obviously depending on the design you are going to have slightly different cutting capacity, but that would give you more torque (not sure how much) and 117 feet per second only 28% higher than the metal saw rather than 73% higher of the 7 1/4″ blade.
Stuart
For one, the arbors are different sizes, so you’d need an adapter. Then, the feel would just be off and awkward.
Maybe it’ll work, but it’s still not the best or safest idea.
mattd
I have used the diablo steel demon blades in my skilsaw and they work great. they are designed for a 5krpm 7-1/4 saw so there is no fear of safety issues (other than normal circular saw issues). https://www.amazon.com/D0748F-Diablo-Ferrous-Knockout-PermaShield/dp/B00008WQ3B
mattd
As a follow up I don’t see why you could not put one of these blades into a 7-1/4″ miter saw and use it to get clean cuts on tubing with minimal heat/sparking. give you a poor man’s dry cut metal saw.
Stuart
That’d be more acceptable, in my opinion. There are some metal-cutting non-abrasive chop saws that are better optimized for frequent metal-cutting use.
Goodnightjohnboy
Whoever asked that question obviously don’t know how to use a circ saw & has been getting the wrong information. A circular saw will cut anything as long as you have the right blade. Several brands make 7¼ metal circ blades. They look like a big ass cutoff blade for an angle grinder. Even better, the Evolution Rage blade cuts steel & aluminum as well as plastic, wood, shingles, etc. Its a BMF. I got 2 of them. They cut ¼” plate all day & don’t get dull. I don’t know if they make them for cordless circs. They have smaller blades. Get yourself a normal size circ saw & you can cut metal. All you need is the blade. You don’t need a metal cutting circular saw. They’re too expensive and have no versatility. I hope his next question isn’t “why won’t a circular saw cut concrete or asphalt?”
Stuart
Just because you can, doesn’t mean you should make a habit of it.
You can put an end mill in a drill press, but does that mean you can do milling? Nope, you’d need a mill.
Jake
First off, as others have said, there are a ton of high quality blades designed for doing exactly that and they work great.
Second, have you ever heard of a variac? Tone down the speed a little bit and you’ve got a great metal saw.
Third, you absolutely can use a drill press as a mill. If you have one small piece you need to do something basic to, there’s zero reason to buy a mill. (or pay someone else a pile of money to do it)
Chris
Yeah, I have the same thoughts in my head… Just buy the right blade and you are on the right track. Like the diablo blade mentioned before. Or a diamond blade for concrete/asphalt… Heck, those are designed for angle grinders in the 6000-7000 RPM neighborhood…
Farid
Other than cutting speed, and perhaps higher starting torque, I would think that at least the shoe would be made out of steel no aluminum, as hot spark and aluminum are not a good mix. I don’t know if magnesium is still used in any of the wood cutting saws but that is another no-no.
Ryan
Yes, magnesium shoes and blade guards are usually found in the higher end saws made today.
Nathan
to add to stuart’s comments keep in mind that rpm speed and that linear speed has another facet behind it. Applied torque. YOur metal cutting cirular saws more than likely provide more torque to the hub so as to deal with the extra forces on the blade tips.
a wood cutting circ saw might not have that ability. Now also it’s about repetitive use. I would say a wood circ saw can do the job – on occasion – with the right blades and a lighter technique. the dedicated metal circ saw will do the job consistently and daily.
Also there are a few dedicated metal cutting blades out there for wood circ saws.
sss
i use my milwaukee 2731 to cut light duty metals with diablo carbide blade with no issues.
here’s a quote from 2731 user manual :
“Cutting Masonry and Metal
MILWAUKEE circular saws are not intended for continuous use in cutting metal or masonry. When cutting these materials, use the correct blade. MILWAUKEE does not recommend using bonded abrasive wheels on circular saws for any application.
WARNING Dust, chips, and grit can cause guard to hang up at any time. If saw is used to cut masonry or metal, reserve and mark it for that purpose only and return it to a MILWAUKEE service facility for cleaning and testing before using it for wood cutting.
Only use accessories with maximum speed rating at least as high as nameplate RPM of tool.”
Jim P.
If you turn a wood blade around backwards, you can cut metal roofing….or so I hear ?
Ryan
That is what sparked this question from me. I’m getting ready to put a metal roof on and my buddy is telling me this. Idk I hear a lot of ppl say the same but I just don’t wanna tear my saw up. I got to use it today and it was awesome in my book. Thanks to all again.
Pete
Did you get a new saw? Or did you try it on the roofing? What material and gauge is your roofing. Anything is doable but sometimes theres better options….
Maybe buy a beater saw on craigslist?
Michael
This will work but, you will need ear plugs and over the ear protection together. And your neighbors will hate you. You can now imagine the noise level.
rjbphd
I’m deaf, noise problems is not an issue with me…
tim Rowledge
Oh, you’ll hear it alright – from several blocks away! Think of it this way; you’re whacking the metal with the unsharpened back of little blocks of carbide . How efficient is that likely to be? Yes, as an emergency thing you can get away with it, probably, but the noise and clean-up of the resulting “cut” will not be fun.
A proper metal folding blade is not expensive, a good bit quieter, cuts better and isn’t an insult to a tool.
tim Rowledge
“Metal folding”? Damn You Autocockup!
Corey Moore
OSHA and MSHA reg cites the violation as, “Use of a tool beyond it’s design.” Same category as welding a socket to some sched 80 for a common use breaker bar, and I’ve even seen balls busted for EMT and sched used as a cheater. Basically if there’s not a presentable document from the manufacturer stating that the thing in your hand is capable of doing what you intend without hurting and/or killing someone, it’s against the rules lol that being, I was taught and have on multiple occasions; flip the blade to reverse the tooth direction(directs debris away from the user and tool components) and go extremely slowly. I wouldn’t go so far to advise this method to anyone, being a contractor at the mines under MSHA, but I can attest that I’ve had only success myself with siding and roofing. My 2 cents.
The yeti
I have used diamond blades in an old skilsaw to cut thru stucco siding and aluminum window frame . Replacing windows . Old saw chewy thru it like nothing
Pete
I bought the evolution2 saw to cut some complex cuts on mild steel. Its pretty cool what it can do. It doesnt spark but it does chip and the chips hurt worse than sparks from a abrasive cutoff saw!
The blade didnt last very long but it also wasnt the specific metal cutting blade so i have one of those coming and will test it out.
fred
We had both an Evolution 9 inch saw and its look-alike saw from Morse that we used in the field – particularly on roof decking. At first we were a bit skeptical – because the Evolution saw had some trim that looked a bit toy-like to us – but the saw worked. The chips were a bit of a nuisance – but not as bad as dealing with sparks raining down – or what we had become used to when using a nibbler. The Morse Metal Devil blades seemed to perform well – but still had a fairly short lifespan.
firefly
I have the evolution rage 3 and yes the chips hurt 🙁 I thought i was alone but apparently not :). I quickly learn to put on my long sleeves and gloves after the first cut… Aside from the chip it does it does provide a very nice cut.
Alick
Metal cutting blades are 0 degrees or negative rake as i recall. Wood cutting blades positive rake. This is what will be behind the cheat of flipping a wood cutting blade for metal. I don’t like that idea on principle because there’s no metal behind the tooth to support it if you reverse the blade. You’re relying on the brazed joint to hold the tooth against the cutting force.
It’s not difficult to get a metal cutting blade to fit common woodsaw sizes so at least spend the price of a blade. Metal cut blades are also usually made with a blade shape that limits the bite from tooth to tooth. A safety feature.
I have a big 2kw (ish) old metabo circ with variable / constant speed under load electronics and a steel sole plate. It has loads of torque and can be dialled in to whatever linear speed you want. That cut 5/8 aluminium plate just fine. Use a guide fence, a metal cutting blade and go slow. I was new to it so took around 1/8″ cut each pass. For ally use some wd40 to help stop the chips sticking to the teeth or a jet of shop air directed at the cut for cooling. If the saw can do that it should take some thin roofing sheet easily.
Lastly – you’ve got to get rid of the chips someplace and I don’t see any engineering reason why you would want to spray woodchips in one direction and metal in another.
Alick
Just to add – I checked the userguides of mine and some other model saws to see if my memory was working 🙂 My old metabo is a 1600 Watt / 3″ depth of cut saw. It and some of their other larger saws include a statement of “intended purpose” which includes cutting wood, plastic, composites, and metal. Manufacturer’s accessories include blades for composites and metals. The composite and metal blades typically have tooth rake somewhere between +5 and -5 degrees (rake is more like +15 to +20 degrees for a fast cutting wood blade) and these are only suitable for saws with a “very high power motor”.
Recommended speed setting for metal is between 3 and 6 (out of 6) where 3 is 2000 rpm.
There are explicit references to cutting aluminium and brass, various plastics and laminates as well as wood and even asbestos (only by experts) not so much about steel.
So i’d say go for it with the right blade.
fred
We used some blade lubricants that came in stick form. I think we bought some bearing the Lenox brand – but also picked some up locally at Fastenal.
firefly
Thanks Alick, this is why I love this site. Your comment pointed out precisely why the flipping hack work and why it shouldn’t be used.
Jeremy Brown
Don’t flip your blades! This is really hard on them, and can sometimes knock a tooth loose, so they can’t be sharpened. It’s slow and hard to get a clean cut too. Abrasive blades are no good, the grit messes up the shoe and is horrible for things like bearings and motors. Diablo makes cheap thin kerf metal blades that are the correct profile for metal work, triple chip instead of atb grind on the teeth. under 20$ the last time I bought a couple. They are a great addition to any kit. Good on steel, good on any awkward material that likes to catch or chip, like abs or for sheets of fiber reinforced plastic, or solid surface counter top material . They make expensive full kerf steel ones too, but they are slow to cut, bog down easily and are 4x the price. Proof is in the pudding, despite having metal saws and a wide selection of blades available, most people in the shop reach for the thin kerf 7-1/4 Diablo and the Milwaukee fuel saw after a few times using other choices.
There is one exception, aluminum 3/16 or less cuts much better with a used plywood blade. Cleaner, faster and straighter cuts. Thicker and it bogs down so the advantage is lost. After a month or two on plywood, polyethylene sheet and melamine, they are retired and used for aluminum only. This gets two uses out of each blade, and a new one is a little too grabby on aluminum.
Mario
Seeing as Milwaukee is very end user specific with a lot of their tools, I have to mention that the metal cutting saw is an electrician’s best friend. Cutting EMT, threaded rod, unistrut it works wonders!
Now as far as why you would choose to have a metal cutting saw and now just have a metal cutting blade in your regular wood circular saw, again from Milwaukee’s standpoint I’m sure having another tool to sell helps but also as I stated above they do a good job designing tools for the end user. And the metal cutting saw I think is geared towards the commercial electrician. Other guys mentioned how the guards and blade speed could be factors. I also wanted to mention that the saw itself is lightweight and more compact than your standard circular saw. There’s been countless times where I myself or coworkers have used the metal cutting saw while standing on a ladder or up in the air on a scissors lift. Not to say that you couldn’t with a wood saw but it helps with it being smaller in size and less cumbersome.
I guess ultimately it comes down to how much one is going to use the tool. Someone like myself, an electrician, uses and prefers a tool specifically designed for cutting metal. But a typical homeowner would probably do fine with a wood cutting circular saw and if needed a metal cutting blade that fits in the wood saw.
Just some good for thought.
fred
When Makita, Milwaukee et. al. introduced cordless bandsaws – our plumbers gave a big yippee. I think that I like that tool better for cutting metal shapes, rods, unistrut, etc. For tubing – being a plumber at heart – I still like the cleaner edge provided by a wheel cutter or lathe-style cutter for shower drains and the like.
Dwain (oztooltalk)
Great article, thanks Stuart. I’ve been asked them same a few times.
Goodnightjohnboy
I’m sure they wouldn’t make a metal cutting circ blade if it wasn’t intended to be used with a reg circ saw. Same goes with a masonry blade. They’ve always worked for me. I’ve never had any issues with my saws afterwards. Just be sure to blow out your saw when your done. Especially when cutting masonry. Don’t believe the hype on what Milwaukee says about what a saw is intended for. A 10,15 amp saw will rip through just about anything. They wouldn’t make the blades if that wasn’t the case. It might be a little hard on the saw, but so is cutting lumber. And I don’t think any of these F. I. ‘s read what you need it for. The man asked about cutting metal roofing. He didn’t ask about cordless bandsaws or what BS osha says about using tools or blade rake.
Dave
Used an old circular saw for cleaning caulk and backer rod out of cement joints with just a cheap, dull, $1.99 Menards special blade that had had a hard life cutting up pallets for the Maple sap boiler. The blade worked just fine doing what a pressure washer and screw driver would not do.
Steve
I would hope to do it the other way around. Use a metal cutting saw to cut wood, with the right blade of course.
joe
What about the opposite? Can I properly cut wood with the metal-cutting version of the saw?
I would like to buy a circular saw (Makita in order to reuse the same battery I have) and use it for both cutting wood and metal, mostly wood.
Will models like DSS501Z, DCS550Z be good for that if I choose the proper blade?
Stuart
“Properly?” No, I don’t think so.