Thread: Changing saw blades. Will it affect riving knife?

The riving knife thickness should be on the larger side of between the kerf width and the saw body thickness (the thickness of the steel plate, not the tooth; usually 0.6-1.0 mm smaller than the kerf). The 2.8mm blades should still have enough clearance, the 3.2mm might be pushing it.

If riving knife is too thin the timber can bind on the back of the blade and potentially result in SERIOUS kickback.

Thin-kerf shouldn't be an issue, but you might need to hunt down a suitably thin riving knife to go with it.

Originally Posted by elanjacobs

The riving knife thickness should be on the larger side of between the kerf width and the saw body thickness (the thickness of the steel plate, not the tooth; usually 0.6-1.0 mm smaller than the kerf). The 2.8mm blades should still have enough clearance, the 3.2mm might be pushing it.

If riving knife is too thin the timber can bind on the back of the blade and potentially result in SERIOUS kickback.

Thin-kerf shouldn't be an issue, but you might need to hunt down a suitably thin riving knife to go with it.

Thanks for that,

I was looking at a 3.2mm blade that had a blade body of 2.2mm and my riving knife is 2.3mm... bit of a close call?

I was only considering a thin Kerf blade as I thought maybe they would fit my stock riving knife due to its rather thin nature (2.3)

Originally Posted by elanjacobs

The riving knife thickness should be on the larger side of between the kerf width and the saw body thickness (the thickness of the steel plate, not the tooth; usually 0.6-1.0 mm smaller than the kerf). The 2.8mm blades should still have enough clearance, the 3.2mm might be pushing it.

If riving knife is too thin the timber can bind on the back of the blade and potentially result in SERIOUS kickback.

Thin-kerf shouldn't be an issue, but you might need to hunt down a suitably thin riving knife to go with it.

How does the thin riving knife cause binding?
I am trying to learn as much as possible so as to be safe as possible here.
I can only picture possibly the wood"pinching" in on the riving knife causing it to get stuck ( binding) then the kickback occurs?
Thanks

Originally Posted by hellofellow

How does the thin riving knife cause binding?
I am trying to learn as much as possible so as to be safe as possible here.
I can only picture possibly the wood"pinching" in on the riving knife causing it to get stuck ( binding) then the kickback occurs?
Thanks

Not quite; if the wood binds on the riving knife it just gets stuck, if it binds on the back of the blade, which is rotating up and towards the operator, it gets thrown in that direction. The size of the riving knife is such that it gives the timber something larger than the blade to grab that won't move. Hope that made sense.

The 3.2 blade is definitely too big for a 2.3 knife. I'd recommend you stay with thin kerf blades a) because they fit the knife you have and, more importantly, b) a thin kerf will put less load on the motor (I'm not entirely sure a 2000W motor would cope with a 3.2 anyway)

Is it possible to purchase generic after market riving knives?

I have a 12" MBS-300 table saw that I purchased second hand that came with two riving knives and two blades. To be honest I haven't really looked too hard however it would appear that the thinner general purpose blades kerf is too thin for either knife.

I understand that each saw would have different profile knives which would make after market knives difficult but is there somewhere that actually sells different thickness riving knives? There is always a lot of talk on the forums about getting new riving knives, however I haven't seen anybody provide details on where they can be purchased.

Cheers

Stinky

Originally Posted by Sir Stinkalot

Is it possible to purchase generic after market riving knives?

I have a 12" MBS-300 table saw that I purchased second hand that came with two riving knives and two blades. To be honest I haven't really looked too hard however it would appear that the thinner general purpose blades kerf is too thin for either knife.

I understand that each saw would have different profile knives which would make after market knives difficult but is there somewhere that actually sells different thickness riving knives? There is always a lot of talk on the forums about getting new riving knives, however I haven't seen anybody provide details on where they can be purchased.

Cheers

Stinky

Google was surprisingly unhelpful. All I got was this mob in America: Splitters and riving knife packages and they have a HUGE wait time. Other than that you'll probably need to go to whoever made your saw or befriend someone with a laser/water jet cutter.

Thanks for all the replys. ( and in the thread on what blade to get).

So to clarify the original question about the instructions. The blade body should not be thicker than the riving knife as this will cause the stock to bind to the blade rather than the knife?

I should think 2000 watts is enough to power the blade however as many site saws have these specs and have 3.2 kerf blades?

Finally remember my blade body is 2.2 and riving knife is 2.3, it's the kerf that is 3.2...
Should this not be okay..? The kerf will definately mean it will clear the riving knife, and should not bind on it as the blade body is still smaller than the knife?

Thanks again.

So to clarify the original question about the instructions. The blade body should not be thicker than the riving knife as this will cause the stock to bind to the blade rather than the knife? Yes

I should think 2000 watts is enough to power the blade however as many site saws have these specs and have 3.2 kerf blades? OK, never been in the market for one so it was just a thought.

Finally remember my blade body is 2.2 and riving knife is 2.3, it's the kerf that is 3.2...
Should this not be okay..? Personally I'd say it's too close, you should really have a 2.8-3.0mm knife for a 2.2/3.2 blade. The kerf will definately mean it will clear the riving knife, and should not bind on it as the blade body is still smaller than the knife?

I'll add my novice question here. I don't have a lot of tablesaw experience but I thought from an operational point of view the main reason for the splitter/riving knife was to stop twisting a cut into the blade and causing kickback. The action of stopping a cut closing onto and pinching the blade would only be an occasional hazard in a stressed piece of timber. How often is the pinch problem likely to occur? When stopping just a twisting action how significant is the splitter to blade thickness ratio?

Originally Posted by Fuzzie

I'll add my novice question here. I don't have a lot of tablesaw experience but I thought from an operational point of view the main reason for the splitter/riving knife was to stop twisting a cut into the blade and causing kickback. The action of stopping a cut closing onto and pinching the blade would only be an occasional hazard in a stressed piece of timber. How often is the pinch problem likely to occur? When stopping just a twisting action how significant is the splitter to blade thickness ratio?

I've never heard the 'twist' explanation before, and can't find a reference to it from a quick google search. It may be a 'by-the-way' feature, but it is certainly not the design purpose.

All timber has internal stresses, some more and some less, and cutting will release some of it. The average amount of movement varies from species to species, but can even vary over the length of a single board. As to how often pinching is a problem, as someone who cuts up rough timber on a pretty much daily basis, I'd say about 80-90% of the time.

Originally Posted by elanjacobs

I've never heard the 'twist' explanation before, and can't find a reference to it from a quick google search.

Checkout this Kelly Mehler video Kelly mehler - table saw - Video Dailymotion

Originally Posted by Fuzzie

Checkout this Kelly Mehler video Kelly mehler - table saw - Video Dailymotion

Interesting, but I have an issue with the whole 'kickback vs. ejection'.

What he calls 'ejection', I (and I'm sure many others) would call 'kickback' in that it throws/kicks the timber back at the operator. As for what he calls 'kickback', it shouldn't (I'm very tempted to say can't) happen if you have a proper height-locking overhead guard (such as a SUVA-type guard) and have proper technique for cutting square-ish pieces off the fence.

While the riving knife may help with 'twisting', that's more of a technique issue. The PRIMARY purpose of the riving knife is to prevent the cut from closing on the back of the blade while ripping.

Originally Posted by Sir Stinkalot

Is it possible to purchase generic after market riving knives.

I understand that each saw would have different profile knives which would make after market knives difficult but is there somewhere that actually sells different thickness riving knives? There is always a lot of talk on the forums about getting new riving knives, however I haven't seen anybody provide details on where they can be purchased.

Cheers

Stinky

I have made my own from toolmakers strip of the correct gauge or old saw blades.
Chapmans made several for us at the Uni for the Wadkin.
I made them a ply template which I test fitted to the saw.
They are still operating here in Sydney.
Any industrial saw doctor should be able to make these for you.
H.