Thread: Steel Cutting Drop Saw Blade

Hi Blute,

the cutting off of metal with high speed circular saw blades has only been possible for a few decades or so. Teeth designs and alloys had to be developed especially for such high velocity. The conventional method used to be a liquid cooled (special cutting oil in watery suspension) low rpm blade with very fine teeth and HSS grade steel (reinforced with e.g. vanadium, chrome, nickel, copper, cobalt or molybdene). The drive of such a saw is usually an induction motor plus reducing gears like a worm drive, mounted on a radial arm, with the blade revolving at around 40 to 160 rpm. This method is called "cold sawing". A machine example is depicted below left, examples of cold saw blades are shown in this link:

http://www.askoinc.com/asko/sawblades.asp

At thousands of rpm, the capacity of a standard circular cut off saw for wood is high, the cutting progress in wood can reach up to a centimetre per second. The same tooth design would stall in metal, its forward pace would be far too big for the density of metals. So the rake of the teeth of special metal blades is virtually zero to zero or even slightly negative (they rather scrape very thinly than cut somewhat thicker, as is usual for wood) and the free running edge behind the cutting edge is much smaller, in order to temper the teeth's progress as well as the loading of motor and gears. The alloys of teeth tips and their blade bonds are the strangest of combinations, all developed to resist or avoid heat, because they run dry without a liquid coolant. These alloys also provide longer life than tungsten carbide tips would offer. These special alloys are rather extremely tough than extremely hard (which would mean chipping and breaking).

You don't necessarily have to buy the blades of the Makitas you mentioned; there are many tool brands and specialist saw blade makers that offer a range of fine options, suited for your particular machine. Hitachi offers some durable examples with titanium tantalite teeth (talk about funny alloys) and they work a treat. Do browse the web and search for tips and brands and this choice will reveal itself.

There is not a big difference between 3000 and 3400 rpm, but the higher the speed, the more disadvantage there is on tougher and denser metals. Aluminium, copper and brass can be processed at high speeds with only slight working pressure, iron and steel require somewhat more pressure to let the teeth bite and high speed generates more friction and quicker deformation of material during the cutting process, which generates more heat. Your machine rating 3000 instead of 3400 rpm is definitely better off then. The Hitachi CD12F depicted below right runs at 1350 rpm. And here are some links to dry cutting metal saw blades:

http://www.toolstoday.com/p-5326-steel-cutting-saw-blades.aspx

http://www.toolfetch.com/Category--Blades--Metal_Saw_Blades-cat.shtml

http://www.amanatool.com/circular-saw-blades/aluminum-non-ferrous-metal-584801.html

http://www.metaldevil.com/index.html

http://www.dynamic-saw-blade-sharpening.com/circular-metal-cutting.html

The other way of metal cutting with conventional grinding discs is called "abrasive cutting". The grit grains in the disc cut and shave metal like teeth do, but since their position and shape are random, their cutting effect is also random and very coarse. Much heat is generated as a result, because the sawing progress consists partly of cutting, but also contains a lot of random material deformation and tearing and even melting. When you have learned to live with the results of that, you will be positively amazed by the clean and loss-free results that special blades will offer. The saving of time and effort spent on treatment of the cut faces afterwards, is an added bonus.

Good luck and greetings!

gerhard

Search for Australian Saw Co on the web and check out their Rotary Hacksaw. Steel cutting TCT blades intended to go into angle grinders and wood cutting saws. 5 inch to 10 inch available, may be more now. As with timber, get the correct size for the tool, you will loose to much depth capacity if you go undersize much, and the speeds will also be a bit slow. Aus Saw Co are in the Airport West area. This blade is the parent of the ones used in the Triton Steelcutter, the battery saws and the big US 14 inch cold cut saws. With the correct sized blade, the saw should cut thin wall MS as quickly and well as it would cut timber. Beware however that the swarf is hot off the saw and plays merry hell with plastic guards. Might even be worthwhile looking at a Steelcutter (fully guarded) from toys 4theboys on ebay ($140) or a cheap dropsaw just to preserve your current one if you value it.

Not necessarily so. DeWalt have had a larger chopsaw (355mm) on the market for a number of years now. I'm sure there are others out there too if I looked.

Hi
I have seen a purpose built Makita cut of saw so equipped with the carbide blade.Not the sheetmetal frame but a solid cast one.
It sliced through a 75 solid bar very quickly and left a great finish.
2 years ago they were $1200, plus they have a very long blade like too,I was told by the retailer.

Grahame

I bought one of the Evolution Rage 3 saws.
http://www.evolutionpowertools.co.uk...ion_rage3.html

I use it solely for wood cutting, I bought it because it was very cheap (the local DIY store had a clearance offer) and I thought I might as well get a saw which wouldn't be destroyed if I hit a nail.

I'm happy with the finish left by the metal cutting blade and the cutting speed, however I haven't found any nails as yet, the blade has only cut wood so far.

This is a UK company but there's got to be something similar available in Oz.

the problem i had with using a metal blade in drop saw is it spins to fast as indicated,

i did it any way and had great cuts in 5mm thick angle for about ten cuts then the blade died,

there are not many veriable speed drop saws to slow the revs down to 1800 as required to use these blades.

dewalt sells the old 71/2 that was made by elu, nice saw te other one that is veriable is festool kapex but dont like idea of cutting steel on a $1500 saw