Metal Cutting Circular Saws

[EddyCurr]

In the "How To Cut Navel Brass Thread" there was discussion of circular
saws for cutting metal.

Although aware that blades described as for non-ferrous materials are
available for use in woodworking table, circular and mitering saws,
I was unaware that purpose-built metal cutting circular saws were on
the market. The availability of such saws and remarks about the thickness
of ferrous material that people mentioned cutting caught my attention.

They say that [the Northern Tool metal saw] has a capacity of 1/4"
but I've cut 3/4" steel just don't push too hard.

I've cut tons of metal with skill saws, everything from 2-1/2" Aluminum
to 1/2 Steel. I've even accidentaly cutoff 1-1/2 x 1/4 steel angle with a
common carbide woodworking blade. It's perfectly doable.

The first of some questions for those in the know:

1. How do the metal cutting circular saws differ from the wood versions,
   aside from the blade/chip enclosures?
   .
2. When used on ferrous material, are these tools still acting as cold saws
   or have they moved into the realm of hot or friction sawing?
   
   Milwaukee's 6370-20 has an 8" cermet-tipped blade that turns at
   3,700 RPM, which translates to 7,450 SFM. Many times faster
   than the recommended blade speed of up to 350 SFM for a (HSS)
   vertical saw blade.
   .
3. Are people cutting 1/2" & 3/4" in one pass.

.

** =============================

Edit: Corrected blade speed to 7,450 SFM from 3,875 SFM

.

[John Stevenson]

Do a search on Evolution Rage.

[Black_Moons]

I think this is basicly like the cheapo 3000rpm 'cold saws' they sell at harbor freight/princess auto.

They work, but blade life on thick cuts of steel will be VERY low, And the blades likey cost a LOT to sharpen.

The blade life will be low because it does not have enough torque to make a decent cut with a large number of teeth engaged at once, Same reason why high rpm/low torque drills will burn out a drill fast, Its not just the SFM, but the fact if you use much more force then rubbing, it stalls out the tool.


Cermet tiped blades being a ceramic might last longer at those SFM, till you do something stupid and chip em anyway.

Aluminum does a lot better at those speeds, and people have been well known to cut THICK aluminum (4"+) reliabley with good blade life with just normal wood cutting blades and kerosene for coolant.

[Forestgnome]

It's primarily the shroud, and making sure it can deal with the heat.

[Paul Alciatore]

First realize that one of the reasons touted for using carbide tipped blades for wood was that they would just wiz through any nails in the wood without ruining the blade. So a carbide blade for wood does make a servicable metal cutting blade and I have used them for this. But read below.

What is different between wood and metal cutting blades? Well many factors can be optimized for each use. One, is the actual grade of metal or carbide used. Another is the angles ground onto the teeth. And of course the cutting speed and depth of cut or feed rate. All of these can be optimized for the material being cut. They will be much the same for metal cutting saw blades as they are for milling cutters as a saw blade is much like a thin milling cutter. Wood = fast speed, faster feed rate, larger rake angle, and lower quality alloys will work (better ones will last longer). Metal = slower speed, slower feed rate, lower rake angles, use a coolant, and HSS or the appropriate grade of carbide. For metal they are used much like milling cutters.

If you use a metal cutting blade in a wood saw it will be running too fast and will overheat and dull much faster than if it is run in a milling machine at proper speed and with a coolant. So would any milling cutter if ran at too high of a speed.

[John Stevenson]

The Evolution ones gear the blade down to about 1300rpm.
I have just ordered a new blade tonight for my 14" saw, it was £40 inc postage etc.

Old one lasted about 10 months with no problem then I cut some 2" x 1/2" stainless 304 bars up and that shagged the blade, since read on the net others have had the same problem with stainless so I'm not going to use it on stainless again.

It whistles thru 3" x 2" box with 6mm wall thickness and gives a nice square cut with a good finish.

Some jobs I do I used to cut on the bandsaw and then had to mill the end faces to clean up - purely cosmetic. With the Evolution the finish is good enough and on some jobs that can save 2 hours of milling, more than enough to buy a new blade.

[The Artful Bodger]

My metal cutting circular saw turns at about 60 rpm and has a HSS blade. I am really careful using this thing as with a 2hp motor the torque is enormous and I do not want to be in the path of a fractured chunk of HSS.

[flylo]

I posted this before but Google Modern Gobbler & watch the video. This thing is amazing. I bought a used one that cuts up to 3/8" & tried it with no lube & it cut at least the claimed 48" per minute. I was amazed. No sparks,easy to control, cuts like a hot knife thru butter. Check it out.

[gary hart]

Have the Makita 12" carbide blade metal cutting chop saw. Great for cutting tubing and angle iron. Works good on stainless and chrome moly tubing. The motor turns about have the speed of a wood cutting chop saw. Much nicer then abrasive chop saw. Got a good buy on mine off of Craigslist.

http://www.makita.com/en-us/Modules/Tools/ToolDetails.aspx?ID=309

Also have the Gobbler but that only works on flat stock.

[gwilson]

I have been looking at getting a metal cutting circular saw.Only need it for the bronze 1/2" plate,though.

The Milwaukee saw for metal goes 3700 RPM,and is 13 amps. Most wood saws go more like over 5000. The Milwaukee blades have a negative rake on their teeth. Of course,they have shielded blades,too. All these things have been mentioned a few posts back.

I've looked at the Evolution saws also. There are some,like the Saw Devil saws that get quite pricy,over $900.00,IIRC.

[Black_Moons]

You could probley make a pertty awsome slow RPM metal cutting circular saw with a hydraulic power pack, low rpm hydraulic motor and a small metal base.. Just sayen...

[gwilson]

I just checked out the Evolution Rage saw. Not very expensive at all. I wonder if it would cut my 1/2" tough bronze plate?

It has a 30 minute duty cycle,but so do I on a job like that!

[Stu]

I have the Milwaukee saw you mentioned and it is a very nice saw. I have cut 1/2" mild steel plate with it. With a new blade it goes through the 1/2" very easily, on the other hand it does eat up the blade (probably because of the hi RPM). On the job we use it for cutting commercial siding and lighter gauge angles and such. We were told to get the blade up to speed before starting any cut to reduce chipping of the teeth. I have one of those speed reducers made for wood routers, I wonder if that would work with the saw?

Bill

[gwilson]

I have had that idea too,about reducing the speed of a regular saw with the router speed control. I think it might rob too much power from the saw,though.

[Tanto]

With all due respect it's very clear from some responses here that many people have never actually used these blades, and are basing their answers based on what they think are the answers.

Just to cut through the BS a little. TC blades are available to run at conventional speeds used by normal wood circular saws the smaller diameter ones can also be used in angle grinders at even higher RPM (but with around the same surface speed).

They cut all un-hardened metals, however the harder the material the shorter the blade life.

The difference between a steel cutting blade as above and a wood blade is in 2 areas. The tooth design is negative rake and very "solid" in profile, it doesn't look anything like the hook design familiar to woodworking. The other major factor are the chip limiters, they are very large and allow only relatively small chips to be cut. Apart from the obvious safety factor, they allow the teeth to cut properly.