The Truth About Riving Knives

[Music] welcome back everyone in today's video I'm going to talk about driving knives in particular I'm going to talk about my riving knife and why it's not in my table-saw first of all I'm gonna back up a little bit and talk about riving knives and why we have them in the first place table saw manufacturers did not used to put them in table saws they eventually ended up in every table saw as a standard safety feature what the purpose of the riving knife is is that as you're making a rip cut it keeps the kerf open as the wood is passing through the blade the kerf does not close up on the end that's already cut that prevents it from jamming up and causing kickback on you it's supposed to also prevent the board from getting sucked into the blade and shooting back at you kind of like a slingshot effect hopefully you're using a push stick or push blocks so you're not going to end up with your hands in that position ever that you know nutshell is what the riving knife is meant to do as I said all manufacturers even the manufacturers that are producing very cheap table saws are including a riving knife when they ship their table saw now your table saw has the riving knife usually installed already when it leaves the factory there will also be manufacturer specifications on the type of blade you should always be using with your table saw in my case I own a heavy duty jobsite table saw made by rigid what came standard on my table saw when I bought it about 11 years ago was this rigid blade which yes I still have the original blade I took it off on day one because it's a terrible blade of course the riving knife was already installed and all the other safety features the kickback clause and the blade guard could be mounted onto the riving knife at the front of the table saw now these two things that I'm holding my hands left the factory as you see them and they are meant to work together now if you switch the blade to something like this Diablo blade that I bought this is a 90 TPI Diablo blade that I swapped out the rigid blade for on day one several blades down the road but this is the 10-inch blade that I've last used on my table saw that gave me much better results than the factory rigid blade now for this I'm going to use metric I'm just gonna take my calipers here I'm going to put it down on the thickest part of the blade which is the top of the tooth and that gives me two point twenty nine millimeters based on what I have in my calipers now for the riving knife that's two point 26 millimeters now the Diablo blade now how does that compare with the seven and 1/4 inch blade that I currently have my table saw like this one we have one point thirty seven millimeters for the seven and one quarter inch the CalPERS aside I'm going to take my riving knife and put it right up against the blade this is the factory blade the riving knife is only slightly thinner than the blade itself that's what you want you want a riving knife that is thinner than the blade that you are using we're going to see that the riving knife now is actually a little thicker than the blade just by putting a ruler on top of this there's about a millimeter space between the riving knife and the blade that is not what you want if I take the framing blade now put the riving knife up against that it is very easy to see that the framing blade is almost half as thick as the riving knife so when I put a ruler on top of that there's quite a gap there that's the curve from my 7 and 1/4 inch blade that's what I currently have in my table-saw this [Music] you'll be the 10-inch Diablo don't over-tighten these all right this is our factory test third cut 10 inch factory blade that's the rigid blade alright let's look at this straight on I've got all three kerf samples now from all three blades I've got the seven in one quarter inch blade that's the fine cut plywood blade that I've got I've got the 10 inch Diablo which is a finer cut than the factory blade and of course the factory blade the 10 inch factory blade which is the widest kerf we've got a riving knife and that just glides really nicely as you can see nice and easy with the factory kerf the Diablo ten inch blade now we've got a little more friction kerfs not as wide and as I go deeper I'm getting quite a bit of friction so the longer the cut the more the friction this is gonna cause some binding and it's gonna cause some problems so you can see the difference already and even more so with the seven and one quarter inch I really have to force this in fact the riving knife only gets about halfway and it completely gets stuck very very bad you do not want this using the riving knife with a seven and one quarter inch is an absolute no-go using it with a 10-inch Diavolo blade not a good idea because now it's no longer doing what it's designed to do using it with the factory blade or a blade of equivalent thickness to create the same curve is a much better way to go if you're using your riding knife as the kerf test proves the riving knife will only really work with a blade that is the factory blade or a blade of equivalent thickness in my experience when I switched to a 10-inch Diablo blade I started having problems with binding and I actually did get a little bit of kickback because the kerf would jam up on the riving knife in for the longest time I couldn't figure out why that was happening I thought wow my riving knife should be keeping me safe why is this happening why am I getting binding and kickback now that's just my experience with my saw you might have a completely different experience with a different manufacturer that's something you should be looking at when you're shopping around for a table saw you really can get into some pretty serious problems when it starts to catch and bind and then the riving knife ends up doing the opposite of what is designed to do the riving knife really has nothing to do with me switching to a 7 and 1/4 inch blade there are other reasons why I did that I've got a video in the description below you can check that out using the 7 and 1/4 inch obviously gives me the finest Kirk and produces the least amount of dust for me personally switching to the 7 and 1/4 inch was the right move I actually feel a little safer on my table saw with that blade but again that's a personal choice when you shop around for a table saw don't forget to check the riving knife on each manufacturer make sure that it's going to give you the flexibility down the road so that you can switch out different blades if the riving knife is too thick you're gonna end up having to always choose a thicker blade robbing knives can be very effective as safety features they can prevent kickback and I highly recommend using one on your table saw if you can each and every woodworker needs to take responsibility for their own safety and you have to do what you think is right based on your own experience and the tools that you purchased I want to let you know that there are new t-shirt designs in my t-shirt shop you'll see the drawer are down below 40 spring that is where you can purchase the new designs you'll see me wearing a couple of these myself I really like them I'm sure you'll love them too they're high-quality t-shirts show your friends how proud you are to have your wood shop up and running show the world how proud you are making your own jigs and tools if you want to donate to this channel head on over to my donation page right over here please remember to Like share and subscribe if you haven't done so already there are a couple more videos on this side you can watch until next time thanks for watching and have a great day [Music]

Channel: Eric Sorensen

Views: 50,939

Rating: 4.7693524 out of 5

Keywords: Riving Knife, Riving Knives, Riving knife kerf test, Truth about Riving Knives, Kerf Test, Riving knife test, Table Saw Safety, How Riving knives work, Table saw test, Tools testing, Woodworking tools, No Riving knife, Power tools, Blade test, Table Saw Safety Test, Wood Shop, woodworking, Woodworking Tips, carpenter, maker, maker space

Id: PRyE_Hfbh1g

Length: 10min 34sec (634 seconds)

Published: Sun Jan 05 2020