TS Blade Question

[Gene Howe]

On a few other forums, posters have stated that they use a 7 1/4" or 8 /14" blade on their TS. They claim more power, cheaper replacement and no difference in cut quality.

I'm far from a mathematician, but it seems to me that a smaller blade would spin slower at the teeth. Not a problem for the SS but, is the concept valid? I have concerns about my ability to figure the correct number of teeth for different sized blades. I'd like to experiment but don't want to go off on a tangent when someone else has already tried it with a SS.

Any thoughts at all?

[8iowa]

Gene:

It's all about cutting torque at the tip of the blade. Blade manufacturers consider saws designed to run on a std 15 amp 120V circuit as "underpowered". This of course includes the Shopsmith.

On most table saws that spin the blade at around 4000 rpm, you have to live with the cutting torque that's there. If someone wants to do some heavy ripping in something like hard maple the only way to gain more torque at the blade's teeth is to go to a smaller diameter blade. The increase in torque will be inversely proportional to the decrease in diameter.

On the Shopsmith, we can lower our speed to around "M" or "N" and gain torque with our 10" blades. This can also go a long ways to avoid burning in the above mentioned hard maple or other sensitive woods such as cherry. Many "reviewers" are too quick to dismiss the Shopsmith as a weak or inadequate saw, but the Shopsmith in saw mode does have some advantages over other saws in this class.

I'll have to mention that there isn't a free lunch here. While going to a smaller diameter blade or lowering the speed on the Shopsmith gives you a gain in torque, the amount of HP available for cutting is the same. Thus, while a ripping cut on a higher HP saw might only take 10 seconds, when we cut the speed in half on our Shopsmiths, we would need to make the cut twice as long, 20 seconds. This of course is no big deal in order to perform a task that would normally be in the realm of a more powerful cabinet saw.

[dusty]

Very thought provoking subject! I started to dig into it but the gray matter just does not work like that any more. There are so many variables in the Shopsmith drive system; making this a NOT-SO-EASY analysis.

My first question was going to be: Is the horse power available at the outer circumference of the blade different than the horsepower available at the motors output shaft? Obviously, the answer is NO! There are mechanical inefficiencies in the system. But if you ignore those losses (assume a perfect system) - can we answer that question?

[JPG40504]

Very thought provoking subject! I started to dig into it but the gray matter just does not work like that any more. There are so many variables in the Shopsmith drive system; making this a NOT-SO-EASY analysis.

My first question was going to be: Is the horse power available at the outer circumference of the blade different than the horsepower available at the motors output shaft? Obviously, the answer is NO! There are mechanical inefficiencies in the system. But if you ignore those losses (assume a perfect system) - can you answer that question?


Since you are ignoring losses in the delivery system, the answer is yes! We are dealing with 'power' here so time/force/distance are all relevant. That is why 1 HP is 550 ft-lbs/sec.

Torque is ft-lbs. speed is rev/minute feed is ft/sec When 'sawing' they are all relevant. Ya need to consider sharpness and wood density as non contributary, although in real situations, we know it can be very significant(it affects the torque required to 'cut').

[reible]

Hi,

One point you might want to look at is safety. The upper blade guard is designed to work with a 10" blade.

I recall reading somewhere in the shopsmith literature smaller blades are not recommended because of this. This does not cover things like dado blades where the upper guard is removed...

Ed

[rdubbs]

Another consideration in the effectiveness of the smaller blades is that many/all of them are thinner kerf blades. I've been taught that all 120v saws should use thin kerf blades, and they work well for me.

[riot_nrrd]

Another consideration in the effectiveness of the smaller blades is that many/all of them are thinner kerf blades.

Freud makes a 7 1/4" thin-kerf finishing blade that really cuts cleanly, and it does a great job cutting through harder woods. Obviously, you lose some blade height, so there is a trade off. So depending on the wood and the cut, I switch between it and a 10" thin-kerf.

RiotNrrd

[Gene Howe]

Just brought up the Tenryu site and one of their 40 T, 8.25" blades designed for TS use is .079 in thickness. Thinner than the 10" Tenryu blades I'm now using.
I think I'll get that one and experiment a little.
BTW, these are excellent blades. They are on my Skilsaws and miter saws as well.