About that long-promised riving knife for the Unisaw . . .

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Forum topic by runswithscissors posted 08-30-2016 05:45 AM 666 views 0 times favorited 3 replies Add to Favorites Watch
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2127 posts in 1446 days

08-30-2016 05:45 AM

I don’t know whether this type of message is allowed on this forum. If not, please steer me in the right direction.

After much delay and a lot of fiddling with prototypes and tooling, at last I nearly have a small batch of riving knives for the Unisaw ready to go. Still have to do some deburring and assembly, but the end is in sight. This week I will take a pattern in to my steel fabricator for the knives themselves, and will get a quote. Unless someone tells me they need a full kerf knife, I will have thin kerf knives made. The reason is a thin kerf knife will work with a full kerf blade, but not vise-versa.

Anyone planning to install a riving knife should be aware that some sacrifices will have to be made. One is the mount for the splitter/blade guard. The riving knife can’t work with it in place. The other is the blade shroud. Although I was able to keep part of my blade shroud, after cutting away a good part of it, I decided it was only marginally effective. So I removed mine altogether. Dust shoots out through slot in the front of the cabinet. I have toyed with ideas for mitigating this, but inspiration hasn’t struck yet.

You will not be able to use the original throat plate/insert, as the cross bar just ahead of the splitter would interfere. A ZCI is the obvious replacement for this. But what about doing bevel cuts? One solution would be to remove the knife and put in the original throat plate. Or one could make a ZCI especially for bevel cutting. I tried this, and sort of succeeded after much smoke and some bad language. I made mine to work with any blade angle, but the slot is as wide as a regular throat plate, and hardly seems worthwhile. One dedicated to 45 deg. would probably be best. Even so, you might not be able to get full depth of cut with that.

Those of you who talk about “fit and finish” when you review tools will have to choke back your criticisms of this thing. It is essentially handmade, with some parts cut out by hand and a number of welds. As I cannot guarantee that every Unisaw arbor is exactly like mine (I have 2 arbors, and they are slightly different, though not in a significant way). The part of the base plate that “indexes” it to the arbor is a steel cylinder a bit over 2” in diameter (that was a challenging size to chase down). Some of them I actually fabricated myself using a bending machine from HF and my trusty welder. You may have to slightly ream out the hole in your arbor. Best way to do this is with a right angle drill and a 2” sanding drum. It wouldn’t be hard to do it by hand, though, as the cast iron is quite soft.

You would need to provide your own wrenches for installation, though I will provide a special wrench for adjusting the riving knife to align with the blade. There is almost no room in there to work with tools—allen wrenches, or whatever. This was one of the main difficulties I had to overcome, leading to much lost sleep. But what I came up with works extremely well (with my special custom made tool).

When these 15 are gone, I’m not sure what I will do. I already have in mind a small modification I will do if I decide to make more of them. I never really meant to get into manufacturing. I would love to have someone more ambitiious/less lazy than myself take it on. Anyhow, I will try to answer questions. PM me if you want to do a transaction. I will have one “blemished” one, that I originally used in trying different ideas. I will weld the random holes up and generally make it work okay, but it will not be a thing of beauty. Functionality will be okay. I will discount it.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

3 replies so far

View Grandpa's profile


3256 posts in 2096 days

#1 posted 08-30-2016 08:16 PM

Scissors, Do you have a photo of this knife on your saw? What are you going to do pricewise. I am still interested.

View runswithscissors's profile


2127 posts in 1446 days

#2 posted 08-31-2016 01:37 AM

Having trouble with photos (new computer). PM me your email address, and I will send them directly to you.

-- I admit to being an adrenaline junky; fortunately, I'm very easily frightened

View jimintx's profile


131 posts in 1006 days

#3 posted 08-31-2016 02:23 AM

I’m also going to send you a PM so I can get info.
My saw is the white, 36-920 Grand Edition, bought new in November 1999.

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