Table saws, riving knives, and how to trench cut

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Gart

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As I'm sure is the case for many people, during the great panini I took up some woodworking (in no small part due to my wife telling me to find something to do that didn't involve bothering her) and have been steadily expanding my garage workshop ever since. I've so far made do with one of those cheap little table saws you find in the middle shelves of certain supermarkets. It's fine, but has many obvious limitations, and I need something proper.

Something like the Dewalt 745 or Bosch GTS 10J is around the right price, and reviews are generally positive. I'm really just after something that keeps pretty square with a good fence and copes well with plywood and oak boards (hobbyist level usage).

And here's the issue, I've mostly been following the many US-based youtubers who show what amazing projects you can do when manufacturers don't have to be concerned with the safety of the operator ie. no riving knife or blade guard, and dado-stacks galore. Don't worry, I'm not (quite) daft enough to want to run a table saw without safety measures in place, but the riving knife being proud of the blade presents a serious issue as you simply can't cut grooves, or build a crosscut sled...

Of course, those last two statements cannot possibly be true, so how do you do them? Can you buy low-profile riving knives that can be installed in the above (or similar) table saws? I've trawled other threads where the answer is "angle grinder". Do some model saws in the UK come with this type of shorter knife pre-installed? Am I just using the wrong technique, and shouldn't be using a table saw for this sort of joinery in the first place?
 

Gordon Tarling

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I can't speak for other saws, but the Bosch GTS10J riving knife has two heights for use and can be removed altogether. Mine works just fine with my crosscut sled and, while I haven't cut any grooves, I have cut rebates in the edge of ply panels and other parts without removing it.

G.
 

Rorschach

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I made a second riving knife for my saw that sits just below the top of the blade to allow me to do grooving cuts.
 

Gart

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I can't speak for other saws, but the Bosch GTS10J riving knife has two heights for use and can be removed altogether. Mine works just fine with my crosscut sled and, while I haven't cut any grooves, I have cut rebates in the edge of ply panels and other parts without removing it.

G.
That is exactly the sort of information I have not been able to find! It would be so helpful if they just included that in the spec, or am I simply showing my inexperience here? I presume a lot of saws are similar, it would explain why I've seen videos of that sort of use, but then the manufacturer images show the knife/guard combo in all its unhelpful glory!
 

Gart

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I made a second riving knife for my saw that sits just below the top of the blade to allow me to do grooving cuts.
I saw several similar posters doing the same, I was hoping to avoid it, but if it was the only option it's good to know it wasn't a crazy idea!
 

Rorschach

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I saw several similar posters doing the same, I was hoping to avoid it, but if it was the only option it's good to know it wasn't a crazy idea!

Haha, no not crazy. As long as you find a suitable piece of steel it isn't a particularly difficult think to make, just need a drill, a hacksaw and a few files to do it the slow way. I was lucky enough to have a belt grinder, drill press and bandsaw so it probably took me less than an hour to make.
 

Gordon Tarling

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That is exactly the sort of information I have not been able to find! It would be so helpful if they just included that in the spec, or am I simply showing my inexperience here? I presume a lot of saws are similar, it would explain why I've seen videos of that sort of use, but then the manufacturer images show the knife/guard combo in all its unhelpful glory!
The answer to your problem is to seek out the instruction manual, which can usually be downloaded from the manufacturer's website. :)

G.
 

Doug71

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I would suggest not removing the guard from your table saw but instead learning about routers for cutting grooves and rebates etc.

Don't copy what you see US based Youtubers doing, there is a reason why SawStop was invented in America.
 

TheTiddles

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Fitting an alternative riving knife that’s below the top of the teeth is fine, but you need to add an alternative guard above the blade too. Similar for a cross-cut sled, you can make a decent guard into one just fine.
 

Fitzroy

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Steve maskery, formally of this parish, has some great vids on YouTube that show alternate methods of guarding a saw blade without using a riving knife.

I’m personally comfortable using other guarding methods but a fully exposed blade is a no no for me.

Also be aware the function of a riving knife and what the risk is by removing it and then you can make informed choices.
 

baldkev

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The dewalt 745 has a removable knife and guard, and for what it's worth, the parallel fence ( rack and pinion ) is simply fantastic. I also have a bigger fixed machine in the workshop, which I made a new riving knife for, from an old saw blade. Easy to grind to shape, but a pain to drill! I believe sawblades are tempered to stay flat, so are a bit hard.
I am going to make a new overhead guard, rather than fixed to the riving knife.

As mentioned above you can incorporate guards into sleds etc quite easily, just always consider hand placement etc before making a cut.
 

danst96

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This may not be the best advice, so shoot me down if necessary but I personally am comfortable removing the riving knife for a groove cut as long as I am doing shallow passes. My understanding is, apart from holding a blade guard, the riving knife really only functions on a through cut which there will be a high chance of the wood binding at the back causing a kickback. The most likely concern would be the lack of blade guard but again this comes down to experience, type of cut (lots of variables) etc. If you only have a cheap saw I'd say it's not worth going down the crown guard root. Get a decent router instead. Also get a router if your uncomfortable with the above. You'll find heaps of uses for it otherwise and once you get the knack of setting it up quickly, it's easier than doing loads of passes with a table saw which can be difficult especially with larger workpieces.
 

hlvd

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I do this for a living and never take off the crown guard or riving knife, there are much safer and better ways of making grooves such as a router or router in a table.
Those Health and Safety regulations are there for a reason, stay safe.
 

chris.gid

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I have a DW745 and one of the first things i did was buy another blade guard and cut it down to make a riving knife.
I think the US and UK design of the guard is different, my one is a very dark smoked plastic so its difficult to see the blade when its in place and i was more comfortable using the saw being able to see the blade than it being hidden. I don't think the blade guard has any anti kickback teeth on it so while it would stop something getting thrown up in the air i don't think it would stop kick back altogether.
Having had a few near kick back issues i would never remove the riving knife, but to be honest its happened more with real wood than ply and general when i've known its a 'risky' cut and im using push push sticks in both hands.

Maybe I'm ignorant (and again watched too many US youtubers) but it seems like kick back is by far the biggest issue with table saws and the riving knife seems to reduce the likelihood by 99%, if you were that worried by the remaining 1% risk then maybe a track saw (or hand saw) would be the better tool to use.
 

KT_NorCal

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Speaking as an American (who lives in the Wild West on top of it), one of the things that isn't mentioned above is making sure you match the riving knife thickness to the plate thickness on your blade... riving knifes (or splitters as the annoying non disappearing kind are seemingly called over here) can cause some butt puckering if not sized correctly. Also key is maintaining the proper distance between the blade and the riving knife.... so if you have one sized for a 10" blade and then throw in that extra 8.25" blade you have sitting around to "just rip a board real quick" you can get yourself in just as much trouble.
I borrowed a friend of mine's portable Dewalt not to long ago an he informed me he had "upgraded" the blade to a new thin kerf one... turned out to be very close to the thickness of the stock riving knife and presto 6 inches into a cut I had a jammed piece of wood in the saw...

Back to grooving... it isn't really a black art if you are smart about it. As others have noted above it isn't a big deal to buy a second splitter (of the right width) and cut it down so that it is below the top o the blade for running grooves. This is really no different than using a dado stack on the saw.

The thing about grooving and safety is that the board, for the majority of the cut, *is* the guard and completely covers the blade. For building up a bunch of cabinets and especially for MDF materials it can't be beat to be honest. That all said, if you see yourself doing that sort of work a lot the best thing to do is build a sled for your tablesaw that covers the blade at the start of the cut and at the end. It will also significantly upgrade the consistency and quality of the work.

Anyway, there is the crazy risk-craving American input. :)
 

Gart

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Thank you everyone for the very informative replies, I knew I was on the right track asking here.

Primarily I was interested in the crosscut sled, and I have a design incorporating a perspex guard, it was just the current riving knife made that impossible and I didn't want to spend a chunk of money to be stuck with the same problem. I'll go back to my router table for grooves, time to buy a new mitre gauge as my current one is terrible!

Thanks again everyone!
 

hlvd

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I have a DW745 and one of the first things i did was buy another blade guard and cut it down to make a riving knife.
I think the US and UK design of the guard is different, my one is a very dark smoked plastic so its difficult to see the blade when its in place and i was more comfortable using the saw being able to see the blade than it being hidden. I don't think the blade guard has any anti kickback teeth on it so while it would stop something getting thrown up in the air i don't think it would stop kick back altogether.
Having had a few near kick back issues i would never remove the riving knife, but to be honest its happened more with real wood than ply and general when i've known its a 'risky' cut and im using push push sticks in both hands.

Maybe I'm ignorant (and again watched too many US youtubers) but it seems like kick back is by far the biggest issue with table saws and the riving knife seems to reduce the likelihood by 99%, if you were that worried by the remaining 1% risk then maybe a track saw (or hand saw) would be the better tool to use.
Kick back is when the upward travelling rear of the blade catches the wood and pushes it forward at a ridiculous speed. The crown guard stops the wood from coming up so does prevent kickback,
On a long length it’s not so much of problem but short lengths can become dangerous projectiles if the riving knife and crown aren’t in place.
 
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