How Exactly Does a Dual Saw Work?
The Official DUALSAW - The original double blade, twin blade, dual saw
I tried to figure it out when I was looking at one that was on display at a Costco the other day, but I am having a very hard time figuring out the mechanism. The video on the Dual Saw website was not very clear. How do two coaxial saw blades receiving power from the same motor rotate in opposite directions so rapidly while being so close to each other? Is it all gears or are there any hydraulics involved, like in an automatic transmission in a motor vehicle?
Wonder on, 'till all things are known!
An arbor within an arbor
I purchased the Craftsman version a few years ago when it first came out.
Although the claim of neutral cut pull (front to back) was somewhat true as the cutting forces were balanced, the fact that it showered my shop with hot chips turned me off to keeping it.
It went back to the store.
They kinda show it under Videos...0:06 video...
Media - Videos and Images | DUALSAW
As MJK mentioned, the holes thru the blades are different sized and so they run on concentric flanges (which counter-rotate by a single gear reduction). Looks like a part of the bevel gearset inside the rotating "carrier" in a classic truck rear axle.
Anybody use one?
If I may be so BOLD. It looks like an engineer's dream who never cut a board. I sound really negative here, but I'm increasingly becoming aware of new products being designed, and released, by people in companies who never have to actually use them. I'm wondering if this is one of them?
Eli Whitney was building muskets, and he was building them faster by the process known as division of labor. He took ~16 people off building the whole gun, and instead let each one build one specific part of the gun over and over again. It was a big step forward.
Now the idea, design, engineering, and all the other steps of manufacturing are strung out all across the world. The left hand doesn't even know if there IS a right hand. The reason: Very few in the chain have pride in the product. They're only doing the minimum requirement, and many times don't even know what the item is supposed to do.
I'm hoping our pride of accomplishment is still sound, when the work is brought back to the United States.
You expect pride when work is brought back to the United States? When the work is brought back, it will not be the the United States but rather a land that is split into two parcels - Los Estados Unidos de Mexico to the South and Shuanzen District to the North. I'm sure the Mexican and Chinese owners will be very proud.
I have a lightly used Sears version of this that I found at a yard sale cheaply enough to warrant trying it. It is fairly effective, but as MJK notes, it throws burning hot chips everywhere. The blades are expensive and if one catches it can break off teeth. The tool includes a lubricator with some sort of wax that is required to allow the blades to counter-rotate, and when the holes wear a little, it's not enough and they start to bind.
With that said it does cut quickly when used right, and it's pretty clever. I've used it to cut conduit and pipe, which it does pretty quickly when great precision is not required. It's pretty good for chewing a wood surface, as one might do with a chainsaw tip or a chain wheel on an angle grinder. The cut tends to be pretty rough, and the kerf is very wide. For freehand use outdoors where finer cutting tools cannot go, it has some applicability, enough to be worth looking at, but not necessarily worth shelling out money for. I got mine for something like 20 bucks with a new set of blades, and later found a set of new blades at a closeout for nearly nothing. It looks as if the Dualsaw blades are a little cheaper than the Craftsman ones, but it can still get expensive. Indoors or with pieces small enough to put into a machine, there's almost always something that will do the job better or cheaper or neater.
Last edited by bruto; 12-24-2012 at 06:16 PM.
Going through and watching all the videos, it appears like this saw works ok cutting sheetmetal and tubing.
The video where the dual-saw went head-to-head against an angle grinder cutting a piece of 5/8" rebar was downright laughable. They were working hard to keep the angle grinder making sparks without actually cutting off the bar. Any 4-1/2" angle grinder with cut off disk would be able to cut off that rebar in 5 seconds tops.
The problem I find with mine is that, as Philabuster says, it's not great on really thick stuff which an abrasive tool can do better, but it's also not very good on really thin stuff which can catch a tooth and damage the blade. One wrong move on conduit, for example, and you lose a tooth. The range where it works better than other things is small.
I am surprised they work at all, since there has to be SOME clearance between blades, and therefore uncut material wedging in there.
Reminds me of the Wellsaw double-blade reciprocating saw,which I see still seems to be sold for carcass splitting , and the electric carving knife which actually worked okay on turkeys cooked to falling-apart. But so does a real knife, if you bother to sharpen it.
There doesn't seem to be room for anything to get in. It works because the blades and arbors are made with some precision: they rub together as they run, and require a waxy lubricant to keep them quiet. In fact, if there has been a certain amount of blade slippage, enough to wear a part of it, the blades will rub together too much, and the motor will smoke instead of starting unless you loosen the nut a little.
Originally Posted by magneticanomaly
By the way, an electric carving knife may be pretty silly for meat, but it's grand on foam rubber.
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