Thread: Jet JWCS-10 Riving knife

Blade Guard Assembly; Installing Blade; Aligning Blade Guard And Splitter - Jet JWCS-10A Owner's Manual [Page 10] | ManualsLib

Best I can do; good luck.

I'm assuming that what you desire is a rise and fall riving knife. I've never seen a rise and fall riving knife successfully fitted to one of these contractor style saws. They all come with the integrated splitter, anti kick back pawl, blade guard that is mounted on a rod behind the table. For several reasons the splitter/guard is a complete PITA; it only allows full depth cuts, it's a b@#$ard to remove and align when refitting and generally speaking it's more of a nuisance than anything else. Consequently many - most/all? - owners remove the assembly and stick it on a shelf where it can be easily ignored.

There are two main difficulties in fitting a riving knife, be it fixed or rise and fall, to these saws - there is nowhere to fix it to the end of the arbor casting and, at least on my 12" model, there isn't enough room between the back of the blade and the trunnion to fit one anyway. So we need to find another solution. The point of a splitter or riving knife is to prevent the back of the blade from coming in to violent contact with the stock being cut. It doesn't prevent the blade from coming in to contact with the stock, the splitter/knife is thinner than the blade kerf, but it does prevent the blade grabbing the stock and violently throwing it in your general direction (kickback). This is only a potential problem with through cuts as, with partial depth cuts the remaining material holds the saw kerf open - this is assuming that you have a fence that locks down solidly and that you feed the stock accurately.

So, what can be done to reduce the potential for kickback and therefore make the saw safer to use? The solution that many owners use is to make some zero clearance insert throat plates and fit a feather of wood in the plate behind the saw blade. This is a simple and effective solution, it works very well. For it to be as effective as possible it is important to set the blade height significantly higher than the stock being cut to reduce the distance between the back of the blade and the splitting feather, this improves safety. This doesn't mean that you should always run your blade at full height, you need to be sensible about these things, but I would suggest that the blade should always be at least 20mm higher than the thickness of the stock. Running the blade at this greater height also has some other advantages - there are less teeth engaged in the cut so less heat build up in the blade; the teeth cut down into the stock rather than tending to push the stock towards you; there are less teeth coming into potential contact with the cut stock at the back of the blade reducing, although only slightly, the potential for kickback. The idea of having the blade just protruding through the stock seems to me to be a peculiarly American thing and I have not considered it correct or best practice for a long time.

I have never had a case of kickback when using the feather splitters.

Hope this helps.
Cheers,
David

Surely one of us clever buggers can engineer and produce a kit to retrofit knives to these types of saws? I can’t count how many times this has come up on the forum here. The old man’s saws just had a t shaped bracket behind the blade attached to the steel plate that the shafts and motors were on, effectively the trunion, and it had two bolts with oversized locking washers to hold the knife, simple, although his blades didn’t tilt, never quite got around to thinking that out, it worked fine.
Surely there’s an easy, bolt on solution?

That may work on a 10" saw if the 10" uses the same guts as the 12" version. There's about 30mm between the face of the trunnion and the back of the blade on my saw when it's fitted with a 10" blade. Bolting a short splitter to the trunnion would also move the splitter with the tilt, so a more satisfactory solution than the feather splitter in a throat plate insert. I mainly use 10" blades on my saw (I find it a bit scary with a 12" blade installed) so I think I'll have a go at this when I've got the time.

Doing it this way had never occurred to me, probably because of the concentration on trying to achieve a rise and fall riving knife. Thanks for the idea.

Originally Posted by aldav

That may work on a 10" saw if the 10" uses the same guts as the 12" version. There's about 30mm between the face of the trunnion and the back of the blade on my saw when it's fitted with a 10" blade. Bolting a short splitter to the trunnion would also move the splitter with the tilt, so a more satisfactory solution than the feather splitter in a throat plate insert. I mainly use 10" blades on my saw (I find it a it scary with a 12" blade installed) so I think I'll have a go at this when I've got the time.

Doing it this way had never occurred to me, probably because of the concentration on trying to achieve a rise and fall riving knife. Thanks for the idea.

waiting waiting dont tell us you work all day. some of us are supposedly retired you know, we sit around waiting for the bright ones to successfully achieve these results.

I got my contractor saw in 2006 and took the splitter off a few months later and replaced the stock OH dust guard with a Big gulp hood on the end of a dust picker arm. I added a Pc shroud to the Big gulp hood so it covered the blade. If grabby wood can’t rise off the table it can’t kick back anywhere near as easily. Since then the only (fortunately minor) kick backs I’ve have was was when using the TS without the guard. A few years back I replaced the Big Gulp hood with an even heavier PC, thick acrylic and Al hood making if more difficult for any wood to lift off the table. I realize this may not suit everyone and still advocate using riving knives/splitters esp for novices and places like mens sheds

Originally Posted by aldav

That may work on a 10" saw if the 10" uses the same guts as the 12" version. There's about 30mm between the face of the trunnion and the back of the blade on my saw when it's fitted with a 10" blade. Bolting a short splitter to the trunnion would also move the splitter with the tilt, so a more satisfactory solution than the feather splitter in a throat plate insert. I mainly use 10" blades on my saw (I find it a bit scary with a 12" blade installed) so I think I'll have a go at this when I've got the time.

Doing it this way had never occurred to me, probably because of the concentration on trying to achieve a rise and fall riving knife. Thanks for the idea.

No worries, if I get time I’ll get some photos of one of his saw benches to post up here one day, lots of good ideas all over them, and fairly simple solutions to safety issues too, like I may have said before, he built almost 100 of them, and most are still in service, including the original built in 1972.

Aldav pricked my interest and got me looking at options on my TSC Id guess I have even less room, as per pics.

now, I thought, the truion along with the blade can tilt sideways, the blade moves up and down, so I came up with this idea attached. Its just an idea, its it workable? Is it safe?
got no idea but your thoughts.

The knife would be just high enough to work and cut so that when blade was very low the knife would not get in way of timber coming through,
Its mounting to truion would be adjustable with washers to align with blade, the bar coming out to blade mounting bolt allows for raising lowering.

img20220115_15051929.jpg grrrr didnt think if this.............

between the blade mounting bolt and truion bolt I have the following measurements
blade fully lowered 200mm
raised 150mm

Unless I've misinterpreted that won't work, the arbor and blade are spinning so there's no way to mount a stay at the arbor end. But, that bolt that's circled on the attached picture looks like it might be an appropriate place to mount a short splitter. Is it attached to the trunnion?, bit hard to tell from the pic. There's nothing like that on my saw. Any splitter that you made would have to be shaped to stop the possibility of the splitter coming in to contact with the rear of the blade, appropriate shaping of the splitter below the mounting hole could achieve that.

Don't hold your breath waiting for me. I've got a bit on at the moment and am supposed to be going to Qld next week for 3 weeks, but I'll get to it eventually.

Originally Posted by Tonyz

grrrr didnt think if this.............

between the blade mounting bolt and truion bolt I have the following measurements
blade fully lowered 200mm
raised 150mm

Although it would be nice it's not necessary for the splitter to tightly follow the blade curve. I'd be trying to fashion a splitter to be mounted on that bolt, it only needs to be 15 or 20mm higher than the table top.

I jump to crazy ideas without thinking them through situations, as per my post just before.
Then I realised just what you mentioned. Drrr

Yes the bolt circled is mounted as part of treuion

thus we go back to my post TSC 10HB riving knife etc. and riving.jpg cutting part of it off. but its still at one height.

beer o'clock sounds good

just saw you last post.

talk about a dog not letting go of its bone. wanting to succeed has bugged me most of afternoon.
looking at the original rivingknife/blade cover thing, I asked this question on another thread.....

IF I cut this mount and kept just the front section with riving knife and blade cover, could I secure it enough without it working its way onto the blade itself. Or is that just plain dumb stupid?
I was told I had answered my own question and dont do it.
now I am not saying or hinting someone is wrong

Then today Aldav
Although it would be nice it's not necessary for the splitter to tightly follow the blade curve. I'd be trying to fashion a splitter to be mounted on that bolt, it only needs to be 15 or 20mm higher than the table top.

so if I go back to my earlier thinking and use a piece of knife would it work? So piece of MDF roughly cut rivingknife template1.jpg and pushed into old zero insert rivingknife home.jpg it worked.

If I cut the metal one and keep the lip on the back, file the front edge a little more I think we have a winner.

I was under the impression that riving knives needed to be full height of blade but as Aldav said only 20-30mm

All I need is some very fine washers like spacers to get this really tight behind the blade. Iam talking about paper thin type washers any ideas please.

Originally Posted by Tonyz

If I cut the metal one and keep the lip on the back, file the front edge a little more I think we have a winner.

All I need is some very fine washers like spacers to get this really tight behind the blade. Iam talking about paper thin type washers any ideas please.

As far as the washers go I'm assuming you're talking about aligning the splitter with the blade, not moving the splitter forward? If you only need something paper thin consider using masking tape in layers until you get to the thickness you need. I'd be making the base of the splitter so that the rear of it butts up hard against the trunnion just to make sure it can't tip forward into the blade if it comes loose. Looks like you might be on a winner. It'll be a bit more work on my saw, but still well worth doing for 10" blades.