Wide kerf table saw blades safe for non-through cuts?

[uncleswede]

Hi,

Pretty much novice woodworker here.

Is it safe to use a table blade saw that is wider than the riving knife providing it's never used for through cuts?
Basically, I'd like to use a 6mm kerf blade for my DeWalt table saw (which has a 3mm wide riving knife) for box joints using a custom crosscut sled...

Cheers
CD

 

[Jacob]

Hi,

Pretty much novice woodworker here.

Is it safe to use a table blade saw that is wider than the riving knife providing it's never used for through cuts?
Basically, I'd like to use a 6mm kerf blade for my DeWalt table saw (which has a 3mm wide riving knife) for box joints using a custom crosscut sled...

Cheers
CD

Yes. The riving knife has to be narrower than the sawblade anyway or it'd bind. Ideally just a fraction thinner but anything is better than nothing. You can saw through without a riving knife too, but with caution, in case of timber movement snatching the blade. More likely to happen with thicker material.

 

[deema]

No! The riving knife should be slightly larger than the plate of the saw blade, but narrower than the kerf. Using a 6mm kerf blade is highly likely to have a plate size wider than your riving knife. The riving knife becomes useless. You need a riving knife matched to the blade.

 

[HOJ]

use a 6mm kerf blade for my DeWalt table saw (which has a 3mm wide riving knife) for box joints using a custom crosscut sled...

For your intended purposes a riving knife will play no part, you will only need to make a cut just over the crown of the blade, then pull the sled back.

Make sure you do the diligence on extra measures to cover the exposed blade

 

[Jacob]

No! The riving knife should be slightly larger than the plate of the saw blade, but narrower than the kerf.

OK yes that's what I meant - ideally. But a thinner riving knife would still be effective

Using a 6mm kerf blade is highly likely to have a plate size wider than your riving knife. The riving knife becomes useless.

No it'd still help with wandering bits of wood.

You need a riving knife matched to the blade.

Ideally.

 

[Sideways]

Let me rewrite your question as this is in no way worse and probably better:
Is it safe to use a sawblade without any riving knife provided it isn't a through cut ?

It's not impossible for the wood to twist and pinch a little but it won't close up the way a rip cut all the way through can.

Try to clamp something across to give you a crown guard over the exposed blade if you don't have a proper overhead mounted guard.

I wouldn't be handholding the wood to the fence myself. I'd want it clamped and my fingers far away.

 

[Jacob]

....

I wouldn't be handholding the wood to the fence myself. I'd want it clamped and my fingers far away.

Yes i forgot to say two push sticks every time!

 

[Sideways]

Yes i forgot to say two push sticks every time!

I said it for you and then changed it when I remembered that this is supposed to be box jointing using a sled

 

[Eshmiel]

This is a rather strange procedure. Or is it the sparse description of what's being done that's causing some confusion?

If you're using "a custom crosscut sled" to make 6mm wide fingers/slots in the ends of a plank intended as a box side then you should have the workpiece firmly located in position by means of a tab-for-the-slot that's a fixed part of the crosscut sled ..... is that right? You move the plank sideways as each slot is cut, to cut the next one, leaving a finger of the same width between the slots as you do so ..... ? And you're pushing the workpiece on the sled just past the crown of the blade then pulling it back, by moving the sled forward then back, so it never reaches the riving knife .... ?

If so, the width of the riving knife is irrelevant as the workpiece never reaches it. If the workpiece is thick, it may reach the riving knife - but the knife is made redundant by the workpiece being kept aligned by the crosscut sled and its tab (and perhaps a clamp).

The sled with its tab will keep the workpiece moving aright as you clasp the workpiece against the fence of your crosscut sled - although you could increase safety by clamping the workpiece to the sled-fence as well, for each push through the blade, so it can't come loose from the sled fence and its locating tab then skew into the blade and kick back.

How do push sticks come into it?

Apologies if these guesses are entirely wrong. A more comprehensive description of your process might help, particularly what you mean exactly by "a through cut". This could mean that you don't go right past the blade or it could mean that the workpiece is thicker than the blade height so only cuts a groove in the underside of the workpiece when passed right over the blade. I presume its the former, if you're making finger joints - what you call "box joints" ...... ?