Blade guard mod

[Bill in Buena Park]

I've been bugged about the relative chore of installing and removing the stock blade guard on my 21829 (BT3 clone) when switching between ripping and using my crosscut sled. I wanted the ease of removing the guard and having the Riving Knife stay put, a la Sharkguard, but already had a spare RK unit so decided to modify it and my full blade guard assembly to borrow from Lee's clever design.

I took both units to my chop saw, cut the top off the RK unit (so it sits ~1/8th inch under level with top teeth of blade), and cut the bottom off the full-up assembly (leaving enough for mounting on the RK unit), then cleaned up with grinder and files. Took an angle grinder to the top of the RK unit to cut slots, and drilled holes in the guard unit for short bolts with nuts.

The resulting combo works well - RK unit always stays on, and the guard unit slips on and off fairly quickly (presently requires a screwdriver to mount or remove). Pictures below, thanks for looking.

[Turaj]

Bill, thanks for the post and the pictures! I have been thinking about doing something like this as I also have a separate RK but have not done it yet. How long have you used this set up and do you see any issue with the guard being off center ever slightly? And how much cutting height did you lose?

[Bill in Buena Park]

Turaj,
I've been using it about a week now, and REALLY like the ease of installing and removing the guard. Its solid, and I use nuts with integral star lock washers. No issues with the guard being "off center", its so slight, and my guard has left/right play on the arm mechanism anyway. It does require me to make sure the guard is high enough to allow the stock to pass under the plate on the guard assembly. Which means my max cutting height with guard on has been reduced to 2-11/16 inches (so just over 10/4 stock). Anything thicker and I have to remove the guard and rely on the RK alone. Its rare in my applications to rip anything that thick, and this helps me make more frequent use of the guard, which enhances my dust collection through the other guard mod I made for DC.

[Turaj]

Thanks Bill for the info. 2 11/16 is far more than what I usually use so no problem there. I will definitely try it very soon.

[jabe]

Good idea & looks good.

[bongbong]

Bill (if you're still around this site), thanks for posting your mod. Looking at the first photo, it seems like you have to raise the blade high enough for the work to clear the screw heads tightened against the riving knife--I'm guessing it needs to be at least 1/2" higher than the workpiece? Has that been an issue in the year since you've done this?

And now for my really dumb question: couldn't you do this with a single blade guard assembly (instead of two), or did the dimensions not work out?

[bongbong]

Bill (if you're still around this site), thanks for posting your mod. Looking at the first photo, it seems like you have to raise the blade high enough for the work to clear the screw heads tightened against the riving knife--I'm guessing it needs to be at least 1/2" higher than the workpiece? Has that been an issue in the year since you've done this?

And now for my really dumb question: couldn't you do this with a single blade guard assembly (instead of two), or did the dimensions not work out?

Quoting myself here, but I see Bill had actually answered my first question in his reply to Turaj. On my second question, I went ahead and did the mod using a spare guard assembly. Looks like he may have used 2 to get a nice depth for the mounting slots on the RK. Using a single assembly I ended up drilling holes very near the newly-cut top of the RK (<1/8" from top edge). I'll have to keep an eye on it to make sure I don't rip the hole out over time.

Turned out fine, but if anyone's thinking of doing this, make sure to place the new mounting hardware (I'm using wing nut technology) clear of the path of stupid little spacer on the freaking annoying anti-kickback pawl. Or better yet, just cut the pawls off entirely like I did--simplifies everything.

[Bill in Buena Park]

Bongbong,
My apologies for missing the first posting with your questions, but yes, used two so I could cut the one to be the riving knife as close to the top with the welded on stock where the guard arms mount; on the guard assembly one, I cut lower than that point to give me some "overlap" in which to put the fastening bolts. I slotted the RK part, and put holes in the guard part, and this causes me to lose that 1/2 in+ (more like 3/4 in) cutting capacity you describe.

However, in my configuration, the pawls don't present an issue, since the extra material I left on the guard assembly part gives the necessary clearance for my fasteners - but there may be room for wingnuts (just haven't tried yet).

[bongbong]

Thanks for the idea, Bill--poor man's Shark Guard. (One of these days, Lee, I will upgrade... if I keep the saw long enough, and get a dust collection system, and...)

Bongbong,
My apologies for missing the first posting with your questions, but yes, used two so I could cut the one to be the riving knife as close to the top with the welded on stock where the guard arms mount; on the guard assembly one, I cut lower than that point to give me some "overlap" in which to put the fastening bolts. I slotted the RK part, and put holes in the guard part, and this causes me to lose that 1/2 in+ (more like 3/4 in) cutting capacity you describe.

However, in my configuration, the pawls don't present an issue, since the extra material I left on the guard assembly part gives the necessary clearance for my fasteners - but there may be room for wingnuts (just haven't tried yet).

[mageus]

Using just one RK, couldn't you use metal strips that straddle both pieces, a la the actual SG? That way there's no overlap, and you only lose the width of the cut. Based on bongbong's comment, what's the closest one could drill the holes to the edge of the metal?

What's the closest one can make the top of the RK to the top of the blade without getting kickback? Bill used 1/8".

Shouldn't one cut the slots on the lower piece to face backwards? I assume the forces on the guard push in that direction. The SG also has backwards facing slots.

Also, dumb question, but what blade would one use to cut the RK?

[Bill in Buena Park]

Using just one RK, couldn't you use metal strips that straddle both pieces, a la the actual SG? That way there's no overlap, and you only lose the width of the cut.

A true RK needs to be mounted so that the top of the RK is a touch lower than the top of the blade, so it doesn't need to be removed for non-thru-cuts (otherwise the workpiece would hang up on the RK as it passed over it). As such, anything you straddle it with must overlap the top of the RK, whether its the clamp of a Shark (one of which I now own), or my "poor man's" design that only straddled one side. With the Shark's clamp in place, I only lose ~15/32in in blade height.

Based on bongbong's comment, what's the closest one could drill the holes to the edge of the metal?

I leave this to the engineers, but on the Shark, Lee can get the holes within ~1/16in of the edge, which I assume is enough to resist stress failure during a kickback. He also uses pins that are smaller than my bolt/nut arrangement, so more space savings there.

What's the closest one can make the top of the RK to the top of the blade without getting kickback? Bill used 1/8".

Top edge alignment of the RK to the blade doesn't usually bear on kickback - its the flush alignment of the RK behind the plane of the blade on the rip fence side (Loring, am I saying this correctly?)

Shouldn't one cut the slots on the lower piece to face backwards? I assume the forces on the guard push in that direction. The SG also has backwards facing slots.

If I had cut the slots in the other direction (i.e., open top facing the operator instead of away from operator), there's a pretty good chance a kickback would actually push the whole blade guard assembly off the RK toward the operator, since the force is vectored up and toward the operator, as the climbing teeth at the rear of the blade pick up push the stock opposite of feed direction (and a disconnected guard over a spinning blade, in addition to the kickback in progress, sounds like a bad idea). The way I cut them is perpendicular to that force, which should force the guard bolts to stay in the slots.

Also, dumb question, but what blade would one use to cut the RK?

I used a metal-cutting chop saw, the kind like this.

[Stytooner]

Kickbacks generally occur on unguarded blades. That isn't to say they cannot happen with a guard. The guard must be in good shape and aligned well to be useful in preventing kickbacks.
The guard itself really does nothing to help prevent this. The riving knife or splitter is the main player and secondary is it's guard mounting hardware and pawls.
What you might see more often with a guard in place is a fling back where a small part might get jammed and shot forward either into or under the guard.
Any damage I have ever seen from guys on the shark guard has been this type. Never yet from an all out over the top kickback. This force is mostly toward the operator and a bit upward. I know there can be times when the force may go fully upward as well.
I always hammer test these designs to insure that the connection between the RK and clamp are strong enough to withstand this type occurrence.
Two steel pins are actually adequate to hold these properly. I use a third one because guys would turn the clamps around backward and wonder why the pawls never worked correctly. It's an orientation aid that increases strength of the joint.

Anytime your guard does it's job and prevents a true kickback, like above, it needs to be inspected and realigned. Any hard knock on any part of a guard can throw alignment out or do damage. Kinda like an air bag or Saw Stop. If it's employed, it may need work before you can operate BAU.