Riving Knife

[DanC]

I've recently been gifted a free BT3100-1 from a friend who wasn't using theirs, but it didn't come with a riving knife or the t-track insert.

I'm less concerned about getting the original T-track because I'm already making some table extensions and figure I can just try for building it into that so I can ideally make a sled.

So for the riving knife, I've seen a couple on ebay both at kind of ridiculous rates, and I'd rather get one sooner than later. Saw some people have fully fabricated their own, but that starts to seem a sketchy and I dont have anything appropriately thick lying around.

I was wondering if it'd be crazy to just buy a random riving knife, for example https://www.amazon.com/N030675-Repla.../dp/B07KNMD19Z appears to be one one the relatively cheaper side and just drill out new holes and saw off any excess? A fringe benefit of purchasing a real one being that I could presumably buy the rest of the blade guard assembly if i wanted.

[leehljp]

Watch out for the thickness. If you have some calipers, measure the saw blade kerf and don't buy anything thicker than the saw kerf that you use. It doesn't work to buy a thicker riving life than the saw kerf. DAMHIKT. But I will tell you: I made one that wasn't but a fraction of a millimeter larger than the kerf and it did NOT work! The thicker riving knife prevented the wood from moving once the wood was got to the knife.

Most saws use a 1/8" kerf saw blade and most riving knives are 1/8", I think. Ryobi's standard saw blade is Thin Kerf. Forget how thin/thick, but the riving knife cannot be thicker than the kerf or it will jam at the point it hits the knife.

[DanC]

The particular riving knife i linked is 0.087", while my blade's body is 0.071” and kerf is 0.098”. Although, I mostly chose that particular knife because of the price and the shape of the bottom portion. I can do some more checking to make sure I'm choosing one with the correct thickness (although i would have expected OEM knives to be largely inter-compatible with most blades). But my question is largely about whether it's a silly idea to attempt to retrofit a random other brand's riving knife in the first place.

[twistsol]

The one you are looking at would need to be modified to fit the two bolts on the BT3x00 saws and the base of it may not have enough room. Also check out riving knives from thesharkguard.com It's about twice the price of the one you linked to, but it would be made specifically for your saw. Plus sometime in the future you will want to get the shark guard blade guard and then you're set to mount it.

Disclaimer: the site does not receive commission or ad money from the shark guard. They are just really good products.

[leehljp]

PLUS 1 on the Shark Guard!

The reason for having the knife the same or a minuscule less in thickness is - IF it (knife) were wider, lets say by .01 or so, it "could" spread the board wider. Your fence is locked down. You would be jamming the space between the fence and knife, making it difficult at best and probably not at all possible to saw. I did this ONCE only! I was thinking I could force it, but I tried it on 3/4" plywood. Plywood does not give! It just jammed up on the riving knife and I learned my lesson. I was too embarrassed to tell anyone on this forum how dumb I was (about 12 - 13 years ago)!

[LCHIEN]

Don't buy one from another saw and modify

Here is the BT3000 DIY riving knife... sized to allow grooving cuts. With the proper mounting points to the elevating holder locker bracket.
I have been using this for years.
Just need some mild steel plate of the right thickness (.090" or smaller recommended to pass thin kerf blades) and a metal cutting jig saw... Two edges are straight and square so appropriate layout on the blank leave relatively little cutting.
This is a gift from the late Lee Styroon, maker of the shark guard (which may still be available from his sons?)

Lee Styroons BT3 splitter riving knife.pdf

I would buy the riving knife from Shark Guard!!! Excellent product (I have one) if you didn't care to make one. Fitting one from another model saw will be a worst headache!!!

Not sure what part you mean by T-track insert. If you mean the miter slot (which is not a T-slot) then those did not come with the saw from the factory, it was an add on accessory you could buy.
Its not hard to make you own miter slot inserts. But with a good SMT, a lot of people can do without.

[mpc]

Loring beat me to it - posting Lee's PDF file before I could find a link to it. I used that file myself to make a riving knife for my BT3. I have a metal cutting blade for my bandsaw which did the straight and main arc-shaped cut; I used a metal cutting blade in a scroll saw for the small mounting slots at the top of the knife. The small slots are not necessary for normal operation; they just provide future upgrade capability if (when) you purchase the full Shark Guard. Using a drill/drill press to define the circular endpoints of the various slots before making the straight cuts makes cutting the slots quite easy. Raw sheet metal stock is readily available from some home centers or online - McMaster-Carr for example or perhaps Fastenal. I used McMaster-Carr item number 6544K54 which is a 12 inch by 12 inch low carbon steel plate, 0.075 inches thick. They also have one (6544K59) that is 0.090 inches thick; I used the thinner stock because I powder coated mine - thicker but more durable than spray paint. Works great. 12 x 12 stock is enough for a couple riving knife attempts too. You don't have to be precise making most of the cuts - only the mounting slots at the bottom are important - to have an effective riving knife. A file will clean up any problems. Use a file to round over or shape a bevel on the main arc as well to reduce chances of wood kerfs catching the knife.

When you mount the knife, you'll see Ryobi included a bunch of rectangular shims on the mounting points for the factory riving knife+guard assembly. (at least they did... hopefully they weren't lost by prior owners of your saw.) They are just thin bits of metal; you have to determine how many need to be inserted between the riving knife and main part of the support to make the knife line up with your blade. The outside shims are then excess and can be removed. To make it easier to re-insert the riving knife or anything else, a trick posted long ago on this site was to cut an aluminum can into two shim pieces a bit taller than Ryobi's shims... install them onto the factory shim studs face-to-face and then bend the tops (which should be sticking up 1/4 to 1/2 inch above the bracket structure) away from each other, forming a V-shaped funnel to guide the knife. MUCH easier than trying to hold the stock shims in place while futzing with the knife too.

mpc

[LCHIEN]

Good point - you don't need the three feature slots along the top unless you want to mount a shark Guard blade guard to it. Also recommended if you like to use a guard. In that case just buy the shark guard linked elsewhere.

THis is a graphics capture of the PDF file.


Use the PDF and make sure its 100% scaled when you print it so that it will be actual size!

Hint: if you make this, drill two 1/4" (or whatever matches) holes at the ends of the slots and then just make four straight cuts to complete the slots!
And aluminum works well as steel. Easier to work with.

[DanC]

I had discounted the Shark Guard when i saw the topline price of the whole guard setup, but for the price of the riving knife itself, i think that's a small price to pay for knowing it will, for sure, work!

[soichiro]

I just happened to make mine as well using 16 gauge sheet metal from Homedepot and a jigsaw. The shape is based on the original blade guard modified to fit a smaller and thinner blade. It took me several trials but it came out ok. Previously, I made a similar one for a Makita jobsite table saw, and always felt it was little flexy. I will look into the McMaster website as noted in the comment above. I really don't enjoy cutting sheet metal with my cheap Ryobi jigsaw though.