Thread: Blade Height on TS - where is the science?

Does using one, and watching others use them, every day for over 40 years count as scientific research?

I have been using a table saw for 45+ yrs and as far as I can work out there is no science just opinion.

Google-fu

https://www.researchgate.net/publica...r_Saw_Machines

I was watching another thread and then had a look around. There are thousands of Youtubes, blogs and people saying things... but repeated info isn't always right .... right!

I was hoping that from the bloodied fingerless bowels of Freud Research, or such, would be a bit of a thoroughly put together document showing in some detail the actual mechanics behind burning, grabbing, en-flinging, teeth height and well - all things Table Saw.

Not discounting opinion! This is important - but hoping for something with slow-mo videos, repeated tests, and other scientific ruinations

Thanks Pac man!

PDF attached. Not a bad start!

Are you supposed to adjust the blade height to suit the timber you are putting through?

One defence against kickback is a HD close fitting (to the table) blade guard.
Of course this does not mean ignoring other factors, or cover operator riskwhen making cuts in workpieces bigger than the guard can rise, but a such guard can reduce the chances of work riding up the teeth on the back of blade and being lunched back toward the operator.

Other considerations
I don't use a riving knife (although I do advocate they be used).
My default fence is set up to stop half way along the blade.
Large guard has its problems but one of them is not dust collection.
TSguard1.jpg

Here is my Al extrusion half fence attached to a TS fence T-slot.
The Al extrusion comes from a piece I hd lying around the shed.
FF3nce.jpg

Bob, why don’t you advocate a riving knife?

The following is based simply on the physics of how the blade spins and, in my experience, it seems to hold up in reality:

High blade = less resistance to feed, generally safer (regardless of what any youtuber without guards and a riving knife might tell you...I'm looking at you America) because the greatest force is down into the table. If the cut closes, the direction of kickback is more likely to be up into the guard (assuming the guard is properly set to the timber thickness).

Low blade = better surface finish and less breakout (not necessarily 100% of the time, but enough to rely on as a general rule), higher resistance to feed, will be more likely to burn with a dull blade (more teeth in cut = more heat generated). If the cut closes, the direction of kickback is more likely to be straight back at you.

I read in a Leitz catalogue/tech brochure that they optimize their blade geometry for 15mm projection above the timber thickness, but any rough/breakdown ripping should ALWAYS be done at full height.

Originally Posted by Austin_Turner

Bob, why don’t you advocate a riving knife?

Pretty sure he means he doesn't advocate his practice of NOT using one

Originally Posted by elanjacobs

Pretty sure he means he doesn't advocate his practice of NOT using one

Agreed. But then the question becomes "why doesn't he use one?"

Originally Posted by Austin_Turner

Bob, why don’t you advocate a riving knife?

Sorry, my wording was a bit tangled - now fixed.
I DO advocate using a riving knife.
I don't use one because the one on my saw is not colocated with the main saw trunion (It was attached to the crappy old guard which I replaced not long after I bought the saw) and did not rise and fall with the blade. I keep meaning to install a micro splitter - and this may just get me to bring this further up on the todo list.

Bob, I know someone with a saw like that. I made him a bunch of zero clearance inserts so that he could have a range of inserts with different height integrated splitters, and would be very quick to change out. He never used them, but may be an idea for you.

Originally Posted by BobL

I keep meaning to install a micro splitter - and this may just get me to bring this further up on the todo list.

I’d move it to the top of the list Bob. Seriously, a riving knife/splitter is a must have IMO.