Riving knife alignment question

[Anna]

Hi,

I just spent my morning fine tuning my new BT3100. Most of the time was spent on trying to get the riving knife aligned to the blade. I think my biggest problem is/was that I didn't really know what "aligned" means in this case. I tried searching the net for answers, but didn't really find much.

I got the lower part of the riving knife practically in a straight line with the right side of the blade, but the upper portion veers towards the left. I checked the flatness of the riving knife a few times, and it seems like it is flat. It's just that with the nuts tightened, it leans towards the left. I suppose that's better than leaning towards the right where it can pinch the wood against the fence.

I'm just not sure how safe or unsafe this is, or if it's really flawed and I should have it replaced. I did fire up the saw, and it came on just fine. I'm putting off doing my first cuts, though, until I'm sure the setup is absolutely safe.

Thanks for any help.

Anna

[vaking]

I believe riving knife is pretty flimsy. If it in the right place at the bottom but leans above - push it a little and it will take the shape.
You are correct that riving knife needs to alligned with the edge of the blade on the side where the fence is. Most of my cuts are done with fence to the right, so my riving knife is allinged to the right edge of blade.

[Tom Miller]

How much would you say it's veering to the left? Is the riving knife sticking out past the left side of the blade?

If the riving knife is flat, and the blade is flat, then perhaps the riving knife is seated at a very slight tilt. You could try shimming with some very thin material (scotch tape, etc.) on the right side of the riving knife, below the riving knife bolts.

Do you have a zero clearance throat plate (ZCTP) installed? Sometimes a misalignment in the slot can push on the riving knife.

Keep in mind that, depending on the degree of tilt, and the force required to push it straight, it may not be a concern.

Regards,
Tom

[Anna]

Thanks, Alex. I did try to flex it to the right a little bit. Maybe I'll try it again. I was just reading about the Sharkguard, but that's another hundred bucks I'm not sure I want to spend just yet. Will have to think about it some more.

[Anna]

Hi, Tom,

I'll try the shims again. I used paper I had lying around (actually drywall tape), but I didn' try it below the bolts.

I do understand it may not be a concern at all; I just want to be absolutely sure. I'm paranoid that way.

The tilt is very slight (now that I've looked at it again). The bottom right side is perfectly flush with the right side of the blade, but the top portion just overhanging the blade is just a little bit to the left (maybe 1/32"?) of the left side of the blade. Maybe it won't affect the cuts after all. As long as it's not going to cause a kickback, I'll probably leave it alone.

After trying out the shims, that is. I must have installed/re-installed the riving knife a dozen times, trying to get the alignment right.

How much would you say it's veering to the left? Is the riving knife sticking out past the left side of the blade?

If the riving knife is flat, and the blade is flat, then perhaps the riving knife is seated at a very slight tilt. You could try shimming with some very thin material (scotch tape, etc.) on the right side of the riving knife, below the riving knife bolts.

Do you have a zero clearance throat plate (ZCTP) installed? Sometimes a misalignment in the slot can push on the riving knife.

Keep in mind that, depending on the degree of tilt, and the force required to push it straight, it may not be a concern.

Regards,
Tom

[Tom Miller]

I'll try the shims again. I used paper I had lying around (actually drywall tape), but I didn' try it below the bolts.

The shimming I was talking about was in addition to the standard left-right alignment shims -- sounds like you got those shims right, and probably don't need to do any tilt-shimming.

Given the small degree of misalignment, I'd probably just give the top of the riving knife a tug, like Alex suggested. But first, put a thin piece of wood flat on the table between the riving knife and the fence, so that the bending is only occurring on the upper portion.

Good luck, and happy cutting!

Regards,
Tom
p.s. a little paranoia up front is not altogether bad.

[Stytooner]

I don't suggest shimming it with anything other than the shims Ryobi provides. The reason is that it can easily fall out or get lost when changing out the guard.
That riving knife is pretty durable. Just use enough force on it to get the top bent over. It will eventually submit to you will. If you bend it too far, no problem, just bend it back.
If you are having trouble gripping it to bend it, just attach a clamp to it. You should be able to use leverage to get it right.
It sounds like you have the right amount of shims in place. The right side of the blade is where you want the right edge of the knife.
Hope this helps. Holler back if it doesn't.

[RickT]

I had the same "problem" with my riving knife initially. I bent it so it would align perfectly with the right side of the blade. I now have a Shark (Thanks, Lee) and love it.
Rick

[Anna]

Without doing anything to the riving knife, I used the saw this morning to rip some smaller pieces of plywood (about 20" to 30" - used my circular saw to cut the big sheets). It was going okay until I tried to rip a 6 1/2" wide piece to 6". The wood got stuck because the riving knife was a little bit to the left of the blade, and there just wasn't enough wood to overcome that.

I clamped wood on both sides of the knife, and used another clamp to wrestle the top part of the knife towards the right. Seems to work for now, but I wish there's a more elegant way of doing this.

Also, I have decided I hate those pawls. They offer so much resistance that the wood doesn't really glide into them, and they scratch everything. Guess I have to buy that sharkguard after all.

Otherwise, love the saw. It cuts really well, and the cut is so smooth (except for those &^#$% pawls). I'm not even sure about the noise level because I always have my ear protector on. Sticking one end of my Ridgid vacuum to the dust port gets rid of probably 80 or 90% of the dust. I just detach the vacuum to suck up the stuff that gets left on top of the table.

Anyway, enjoying this so far. Thanks for all the help.

-Anna

Edit: I decided that instead of being asterisked out, I'd just supply my own characters to describe the pawls.

[Tom Miller]

The wood got stuck because the riving knife was a little bit to the left of the blade, and there just wasn't enough wood to overcome that.

So, the off-cut side was hitting the leading edge of the riving knife? Maybe you can ease the edges with a file.

Also, I have decided I hate those pawls. They offer so much resistance that the wood doesn't really glide into them, and they scratch everything. Guess I have to buy that sharkguard after all.

Many of us (myself included) remove the pawls for this reason. Others have filed down the teeth to something a little less aggressive. I, personally, don't think they add that much safety, and could possibly cause an unsafe situation by binding the workpiece.

Regards,
Tom

[Anna]

Well I've just given up on woodworking for today. The plywood binds big time. I called Ryobi earlier, and they said what you guys said, which is try to bend the riving knife into shape. Now, although I got the top part to align with the blade, the middle body is still our of alignment, and it stops the wood from going through.

I'll go look up shark guard now. I'm so frustrated about this. Of course I can just take out the knife altogether since I'm currently doing just plywood and there's little chance of the kerf closing in... I think. So unsafe, though. Oh, well.

[bigsteel15]

I'll go look up shark guard now. I'm so frustrated about this. Of course I can just take out the knife altogether since I'm currently doing just plywood and there's little chance of the kerf closing in... I think. So unsafe, though. Oh, well.

I'm assuming you're using the stock blade.
If not then the kerf may be thinner than the riving knife. there are some thin kerf blades out there that fit that bill. I have a miter saw blade that is thinner than my Shark Guard knife and couldn't figure why I was having the same problem.
BTW, I wouldn't remove the knife even when cutting plywood. the danger is not only in the kerf closing in but in the blade picking up the material and throwing it back at you.
If you check around you might find a used SG if you don't have the budget for a new one, or ask Lee if he has any "seconds". Still much better than stock.

[RayintheUK]

Well I've just given up on woodworking for today. The plywood binds big time. I called Ryobi earlier, and they said what you guys said, which is try to bend the riving knife into shape. Now, although I got the top part to align with the blade, the middle body is still our of alignment, and it stops the wood from going through.

I know I've come late to this party, but if you've got the knife aligned correctly with the right-hand (fence) side of the blade, I'm struggling to work out how it can still protrude past the left-hand side of the blade? The knife is certainly thinner than the standard blade kerf, so it must have a fair old kink in it to stop the off-cut going past.

I'll go look up shark guard now. I'm so frustrated about this. Of course I can just take out the knife altogether since I'm currently doing just plywood and there's little chance of the kerf closing in... I think. So unsafe, though. Oh, well.

Given that your original post required a safe setup, I would strongly advise against removing the knife altogether. Although ply may not demonstrate as much kerf closing as ordinary lumber, it's not impossible and there's still the significant risk of binding and resultant kick-back if the piece were to skew, even a little, during the cut. You'll get no warning, just discover how hard 100+mph plywood really is!

Please re-consider and have (yet) another look at the knife alignment. If it's that far out, it needs replacing. While you're at it, get rid of those pawls too - &^#$% nuisance, and as Tom said, can cause more problems than they solve.

I've run my saw without the guard, but I'd NEVER run it without the riving knife in position and the fence absolutely spot on.

(Edit: Looks like Brian got there first, while I was typing! - We're all trying to help you come to a safe result).

Ray.

[Anna]

We're all trying to help you come to a safe result.

Thanks, Ray. I'm not brave enough to use the saw without any kind of splitter and blade guard. My woodworking instructor is very paranoid about safety issues, and I think his paranoia really rubbed off on his students. I'll go take another look at the riving knife. At this point, I'm just so sick and tired of installing/re-installing it.

I'm not sure why the top part was leaning towards the left, but that's moot because I tried to bend it, and now the situation is worse. Am definitely buying the Shark Guard. I guess the saw mobile base will have to wait until I get the SG, and I'll concentrate on my bench again.

Anna

[Tom Miller]

The plywood binds big time....Of course I can just take out the knife altogether since I'm currently doing just plywood and there's little chance of the kerf closing in... I think.

What kind of plywood? I've had big trouble -- the kind you're describing -- with the one piece of Chinese birch plywood (think "potato chip") that I got from Home Depot. And if the plywood is binding, I wouldn't try it without the riving knife!

Keep in mind that the riving knife only needs to be aligned for the 3/4" thickness of the ply you're cutting. So, rather than getting perfect alignment on top, try to get it aligned just above the tabletop. And do try rounding over (filing) the leading edge of the riving knife so that your wood doesn't catch on it.

Are you sure your rip fence is aligned properly? If not, it could be at least part of the problem.

While it's very frustrating right now, you'll figure it out, and it'll all make sense.

Regards,
Tom