scary times

[RogerS]

Needed to cut a rebate out of a 2m length of timber on site. Ended up removing the riving knife and shield from the table saw and started feeding the wood through. All the time I kept thinking about Woody's narrow escape. All went OK ...especially with me leaning my body weight on the timber (after the saw blade) to prevent any chance of kickback.....but a couple of thoughts occurred to me...

1) if the main purpose of the riving knife is to keep the two cut halves apart (to prevent kickback) then why is it thinner then the blade?

2) hypothetically....what is there to stop kickback with a dado set? (IMHO dado are OK if treated with care)

 

[Travis Byrne]

Hello Roger

1) if the main purpose of the riving knife is to keep the two cut halves apart (to prevent kickback) then why is it thinner then the blade?

I believe that the R knife should be the same thickness at the blade.
I also believe that most companies don't want to furnish 2 R knives and that the thin blades are invogue (sp) at this time, thus the narrow knife.
If you had a thicker knife and a thinner blade. Won't work
Thinner knife and thicker blade works--with perhaps bad results. :twisted:

2) hypothetically....what is there to stop kickback with a dado set? (IMHO dado are OK if treated with care)

When using a dado cutter, the wood is not cut in half, thus no chance of wood binding on the blade.

I hope these mutterings are of some help.

Travis

 

[MikeW]

Hi Travis,

Not so. Well, maybe technically not binding in the sense of the cut not closing, but dangerous nonetheless.

The piece being fed over the dado cutter, if it puffins slightly, can with speed kick back. Documented injuries have occured from this, including loss of digits.

I have had such an occurrence, which flung the piece about 30 yards after hitting me in the side. Brusied ribs, cut the fleshy part of my upper arm and it still flew that far. Got all my fingers, though

Woodworking is an inherently dangerous affair. My mistake in moving the piece over the dado could have had worse ramifications. Heck, I've hurt myself with handtools. Power tools can just do it more quickly.

Reasonable care and forethought can prevent most mishaps...just not all.

Mike

 

[Shady]

"Riving knives should have a chamfered leading edge, and should be thicker than the body of the saw blade, but slightly thinner than the width of cut."

In other words, the knife should be thicker than the metal plate of the blade (so that the wood being cut cannot physically 'bind' on the blade, leading to kickback), but thinner than the kerf produced by the teeth, so that the cut is not interfered with by it, in the normal run of events.

Roger: if it is actually thinner than the blade (as opposed to thinner than the 'set' of the teeth), then it isn't as effective as it could be - I'd get it changed...

 

[Woodythepecker]

Roger, i can say without a doubt that kickbacks (the non money type) are not good and are usually very painful , so unlike me stay well clear of them

Seriously, i think that the two biggest cause's of kickback type accidents are the lack of concentration and rushing to get the job done.

Regards

Woody

 

[frank]

roger the riving knife on my old clarke t/saw raised and lowered with the blade, i cut the top of the r/knife to be just under the top of the blade and i was able to cut grooves in the wood with out the fear of the wood binding behind the blade, alas i cannot do this on my woodford,

frank