Quote:
Originally Posted by HitchC&L
What are the advantages of those. I have seen them around but never paid too much attention to them.
Basically what is their job?
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Wood will often have internal stresses that will 'react' when your blade cuts into them. If those stresses make your two rips 'come back together' they will bind into the (back) sides of the blade and cause (possibly a severe) kickback.
The riving knife will keep the necessary separation in the kerf near the back of your blade.
When the pieces start squeezing the blade, - - it causes more friction and
heat, - - which then creates a
wobble and increases those chances of kickback even more.
Another way to avoid that kickback is, - - once you realize you're
binding, - - bring the wood back towards you and re-cut (another kerf-width off)the scrap-rip as you go. You may have to do this several times as you proceed through the cut.
(Don't try this at home) . . .
A more powerful saw (like a cabinet saw) will lessen the problem considerably.
Always play (what if??) safe and don't stand directly behind the cut . . .