Table saw blades smaller than advertised

[Mike Henderson]

I bought a SawStop PCS table saw a while back. Today, I went to put a Forrest Woodworker II blade on it. I discovered that the Forrest blade is not 10" in diameter - it's about 9 7/8". And, no, I've never had the blade sharpened.

I can't drop the riving knife down to fit a 9 7/8" blade - the riving knife actually sticks up above the blade. I discovered this when trying to cut a groove in a piece of wood. Once the wood passed the blade, it hit the riving knife and rode up on the knife.

I then started checking all my blades and found a brand new (never used) Freud blade that was the same diameter - about 9 7/8".

I'm wondering what other people have found with their blades, and how have you addressed this problem. I suppose I could buy another riving knife and grind a bit off the top.

Is it common to find table saw blades that are less than the specified 10" in diameter? Prior to riving knives I suppose it never made any difference but with a riving knife it sure causes problems.

Mike

[John Gornall]

9 7/8" - 25 cm - probably the standard size in most of the world. Sawstop better catch up with suitable riving knives or are they adjustable?

[Mike Henderson]

9 7/8" - 25 cm - probably the standard size in most of the world. Sawstop better catch up with suitable riving knives or are they adjustable?
You can adjust the height of the riving knife (with some difficulty) but many other blades are 10". In fact, all my other blades are 10" except these two.

So if I set the riving knife down for the 9 7/8" blades, it will be too low for the 10" blades. I'd rather have two riving knives if there's no way around the problem and switch them when I switch blades.

But in any case, the blades are specified as 10" blades. Not close to 10" or some metric measurement, they're specified as 10" blades. It's not unreasonable to expect to get a 10" blade when that's what's specified.

Mike

[Kyle Iwamoto]

Just grind the 1/8" off of the top of the riving knife. Can't tell at all. The knife doesn't seem adjustable.

[John Gornall]

Freud blades are made in Europe and checking the Freud UK website they are shown as 250mm diameter. I wonder if they make 10" blades for the USA market. I'd call Freud.

[Mike Henderson]

Freud blades are made in Europe and checking the Freud UK website they are shown as 250mm diameter. I wonder if they make 10" blades for the USA market. I'd call Freud.
Here's a picture of the blade. Note on the left side, in BIG letters, it specifies 10", not 25cm or 9 7/8". It seems reasonable to me that I'd get a 10" blade when it's specified as 10".

They also specify a 5/8" arbor and 1/8" kerf and those are correct.

Mike

[Mike Henderson]

Just grind the 1/8" off of the top of the riving knife. Can't tell at all. The knife doesn't seem adjustable.
The knife is adjustable but not easily. But if I grind 1/16" off the knife (since only the radius sticks up, not the diameter) the knife will be low for 10" blades.

Mike

[Van Huskey]

I have found quite a few discrepencies in even the highest quality tooling. This is interesting, let us know what you ferret out.

[Eiji Fuller]

I'm not sure why/how a riving knife 1/16" low could cause any problems unless your ripping 1/16" stock with the blade just barely cutting thru.

[mreza Salav]

some blades (like FWWII) are 25cm and some are 10".
I have a sawstop too and don't have to adjust the riving knife height every time. what you could do is to have the knife very little (like 2mm) further back, that allows you to have it at the height of a 25cm blade and when you install the 10" blade it still won't hit the knife. I hope it's clear what I mean.
BTW, this is not just for sawstop. Any table saw with a riving knife will have this issue.

Having said this, what you didn't say about having to adjust the blade brake every time. That one, you have to adjust every time you use a different size blade (I hope you didn't miss this one).

[Jim King]

3/4 plywood made here for the US market is not quite 3/4 inch as it is metric in thickness but 4 foot x 8 foot sheets.

And dont forget the real size of a 2 x 4 .

[Mike Henderson]

I guess I'll bite the bullet and do the adjustment of the riving knife to drop it down a bit for 25cm blades.

Good point about the blade brake. But I'm not going to adjust that for 1/16" differences in the radius of the blades. I'll send a note to SawStop and see what they say about it.

Even if you had a 10" blade, you'd lose some diameter when you had it sharpened so there must be some tolerance to the brake.

Mike

[mreza Salav]

If the distance of the brake is more than what it's supposed to be (about thickness of a dime) it will take longer for the brake to engage the blade in case of an accident.
But if the distance is less than what it's supposed to be (e.g. installing a blade larger than the previous setting) the brake can engage; however often it will detect it before even starting the saw and gives you a warning though...

[Jim O'Dell]

My Infinity 50 tooth combo blade is 10" on the dot. But my riving knife (G0691) is right at 1/4" lower than the teeth. Specs if I remember right are 2 - 5 mm below, so this is in specs. If I had a 9 7/8" blade, it would be about right. I asked about adjusting it up. They said no. Looking at it, I could adjust the gearing mechanism 1 tooth, but who knows how much difference that would make in the riving knife. Probably should have tried it when I had the top off. WAY TOO MUCH TROUBLE to do it now. :D Jim.

[Jay Allen]

If the blade is too far from the brake cartidge the saw will not even start. I ran into this a year or so ago with a blade that was a bit small to start and had been sharpened several times. I adjusted the cartridge and it started right up. It's a simple Allen wrench adjustment.

[Van Huskey]

I went to the shop measure blades. I didn't measure every Forrest blade I have but just ones I am absolutely sure have not been sharpened most of these I had to remove the coating to check. Everyone was closer than 1/16" to being a full 10". I checked a WWII 20T, 30T, 40T, 48T, a Duraline and a 80T and 90T Chopmaster blades. I checked 7-8 Freud Industrial blades including 2 P410 Fusions and they were all right at 10" (within 1/32 to 1/64) and my one lone unused Tenryu Gold Medal was also within the same spec.

Not sure what is going on here.

[Mike Henderson]

Here's some pictures of a few of my blades.

First is a Tenryu gold medal. You can see in the second picture that the furthest extents of the tips of the carbides are a bit over 10".

Next is the Woodworker II. You can see that the furthest extents of the carbides are just a hair over 9 7/8".

Last is the Freud which is less than 9 7/8" - about 9 13/16".

I feel confident in the accuracy of my rule. If it was off, the Tenryu should have measured a bit under 10".

Mike

[Gene Howe]

Mike,
If you have a Tenryu, why mess with any of those lesser blades?:D
Every saw I use now has Tenryu blades. Not cheap, but excellent blades.

[Will Overton]

If the blade is too far from the brake cartidge the saw will not even start. I ran into this a year or so ago with a blade that was a bit small to start and had been sharpened several times. I adjusted the cartridge and it started right up. It's a simple Allen wrench adjustment.

I agree, it's a 15 second adjustment when you're installing the blade, no big deal.

As for the riving knife, I would adjust it for my smallest 10" blade and not worry about it. When you start a through cut [of course the blade guard should be installed] just make sure the blade is raised high enough so the knife extends through the cut.

[doug faist]

But if I grind 1/16" off the knife (since only the radius sticks up, not the diameter) the knife will be low for 10" blades.
Mike - I had the same question; why would it make a difference if the knife was a bit lower than the teeth.

I have a Laguna saw and the riving knife is adjustable forward and backward, and up and down. I keep it about 1/8" below the level of the teeth for all cuts, through cuts and dadoes. Seems to work well.

Please let me know if I'm missing something here.

Doug

[Mike Henderson]

Mike,
If you have a Tenryu, why mess with any of those lesser blades?:D
Every saw I use now has Tenryu blades. Not cheap, but excellent blades.
The problem with the Tenryu is that it's not a full 1/8" kerf (it's just under 1/8") so the wood is a bit tighter on the riving knife.

But it is a very good blade.

Mike

[Edit: The riving knife is narrower than the Tenryu blade but the Tenryu blade is less than 1/8". The Tenryu blade is 0.111" while a 1/8" blade is 0.125. The riving knife is 0.090"]

[Mike Henderson]

I agree, it's a 15 second adjustment when you're installing the blade, no big deal.

As for the riving knife, I would adjust it for my smallest 10" blade and not worry about it. When you start a through cut [of course the blade guard should be installed] just make sure the blade is raised high enough so the knife extends through the cut.
That's what I wound up doing.

I found out something in the process. If you put the riving knife too close to the blade, the system detects that it's too close and the saw won't start up. So if you set up your riving knife for the small blades, make sure it's set far enough back so that when you put the larger blade in, the riving knife is not too close to the blade.

You'll get a solid red and a blinking green.

Mike

[Brian Penning]

This has been brought up before. I ground down my riving knife.
The important thing is getting the correct gap between the blade and cartridge.

[Will Overton]

Thanks Mike, good info.

Brian,
Why did you grind the knife instead of adjusting it? There's just 2 set screws for the height adjustment IIRC.

[Brian Penning]

Thanks Mike, good info.

Brian,
Why did you grind the knife instead of adjusting it? There's just 2 set screws for the height adjustment IIRC.


Couldn't get it low enough.

[David Christopher]

sounds like the riving knife is more trouble than its worth...my 58 uni dont have a riving knife and never had a problem

[Jeff Bratt]

This is apparently nothing new. I measured a Freud blade I bought some years ago, and it is also 9 7/8". The domestic made blades I have are 10". I don't have any blades from Forrest... Interestingly, my Infinity blades look to be 9 15/16" - maybe they're trying to split the difference. What are the specified tolerances for blade dimensions, anyway?

This is simply fallout from the imperial/metric discrepancy, and will likely continue as long as there are different "customary" measurement systems. The time when the US could dictate standards to the world has passed. But it would be nice if the actual measurements were stated.

I would be most worried about making sure the clearance between the SawStop blade sensor/brake assembly and the carbide tips is within working range. What's wrong with setting the riving knife low enough to use the smaller blades and just leaving it there?

[george wilson]

My Forrest blade was also 9 7/8". That seems to be about standard for all of them.

[Tom Welch]

I have the same problem on my Jet Deluxe Xacta saw. I run a FWWII and the riving knife is taller than the blade. Which makes the riving knife useless for non thru cuts. First I thought it was the Jets fault but as Mike pointed out the blade is not a 10" blade. Mike thanks for pointing this out.

[Joe Leigh]

Not a problem with the PM2000. The slot cut in the base of the riving knife allows plenty of adjustment and I keep it 1/8" below the top of the blade.
Why not just adjust it slightly below the 9 7/8" blade and it will be fine for the 10" blades as well.

[Lee Schierer]

I'm not a big fan of riving knives, but I always thought that they were supposed to be removed when doing groove type cuts.........

[Joe Leigh]

I'm not a big fan of riving knives, but I always thought that they were supposed to be removed when doing groove type cuts.........

Not necessary if the riving knife height is set properly.

[David Woodruff]

Not sure what is happening either. I can buy the 25mm vs 10". If a blade is 25mm and stated as 10" that should make the 10" blade only .4mm or .0155" smaller in diameter, not even close to 7/8" or .125". Maybe the 2" x 4" anomaly has penetrated other sacred areas in our lives.

[Will Overton]

I'm not a big fan of riving knives, but I always thought that they were supposed to be removed when doing groove type cuts.........

The plus about a riving knife is that you don't have to remove it. Because of that, it's figured that most people will leave them on. One of the biggest excuses folks give for not using blade guards is that they are a pita to take off and on.

Another plus for a riving knife is that it maintains its proximity to the blade as it is raised and lowered. SS solved that by having the splitter/blade guard raise and lower with the blade, just like a riving knife.

My riving knife will mostly stay in its nice little storage slot on the side of the saw. For those few times I might use it, swapping between it and the guard takes less than a minute on the SS.

[Mark Ashmeade]

Thread diversion alert - Mike, your steel rule appears to be calibrated in half-inches on the lower scale. What's that scale used for?

[Tom Walz]

Forrest has been doing that for years. My WWII is maybe 7 years old and is 9 7/8".

When they top grind a blade during sharpening it shouldn't take more than 0.010' or so off.

[Mike Henderson]

Thread diversion alert - Mike, your steel rule appears to be calibrated in half-inches on the lower scale. What's that scale used for?
That's so you can find the center of something easily. Let's say that you measure something with the top scale and it's 22 5/8". If you go to the bottom scale and find 22 5/8" you'll have the center of the object.

It's much easier than trying to do the division in your head.

Mike

[For those of you who posted the suggestion for setting the riving knife for the smallest blade, that's what I did and it seems to work fine. See post #22 for some additional discussion on a "gotcha" on the SawStop when you do that. It has to do with when you put your big blade back in.]

[Mark Ashmeade]

Thanks! Great idea.

[Mike Henderson]

Thanks! Great idea.
BTW, Lee Valley sells those rules but I'm sure others do also. If you buy one, don't bother with the 12" one - I have a couple and never use them. The 24" is the one I use all the time.

Mike

[mreza Salav]

[For those of you who posted the suggestion for setting the riving knife for the smallest blade, that's what I did and it seems to work fine. See post #22 for some additional discussion on a "gotcha" on the SawStop when you do that. It has to do with when you put your big blade back in.]

I think the issue of thinner blades is a different issue than the original issue of height of riving knife. For this new problem, if you have a thin washer (like those that come with dado blade sets as shims) you can use it on the left side of the blade to bring it's right side on the same line as riving knife (assuming that you have your fence on the right of the blade).
Given that the front edge of the riving knife is a wedge shape it should clear the cut-off side easily (as it's not trapped between the fence and riving knife).

[Van Huskey]

Another plus for a riving knife is that it maintains its proximity to the blade as it is raised and lowered. SS solved that by having the splitter/blade guard raise and lower with the blade, just like a riving knife.



All the current RK saws AFAIK work the same way. If you subscribe to the idea all RKs are splitters but not all splitters are RKs what you have is a low profile RK which does not support the blade guard for non-through cuts and a high profile RK which holds the blade guard for through cuts.

Lee, what is your issue with riving knives, I understand disdain for splitters but not sure why someone would not like riving knives.

[Mike Henderson]

I think the issue of thinner blades is a different issue than the original issue of height of riving knife. For this new problem, if you have a thin washer (like those that come with dado blade sets as shims) you can use it on the left side of the blade to bring it's right side on the same line as riving knife (assuming that you have your fence on the right of the blade).
Given that the front edge of the riving knife is a wedge shape it should clear the cut-off side easily (as it's not trapped between the fence and riving knife).
Note that when I posted what you quoted, I was speaking of the diameter of the blades and not the thickness.

What I found with the Tenryu blade, which is a bit narrower than 1/8", was that it was a bit harder to push wood through the saw. I assume that's because it was dragging a bit on the riving knife.

When I set up my riving knife (RK), I align the RK with the plate of the saw. I haven't measured, but I think a saw like the Tenryu has the same thickness plate, but the carbide is not quite as wide. If so, you wouldn't need any shims when installing a thinner blade. I'll check the thickness of the plates next time I'm in the shop. One problem is that all my precision measuring equipment (micrometers) are in metric and not English.

Mike

[I went and checked the thickness of the plates and all were within 1/64". The Tenryu was the thinnest (by 1/64"). All the rest were the same thickness.]

[David Woodruff]

I think I know what happened to the missing 1/8". When the TC inserts are welded in the saw is 10" dia. Then the TC teeth are ground and sharpened. It is like the 2" x 4" thing. A 2" x 4" is just that until it is planed 4 sides, then it becomes a 1.75 x 3.75 or recently I have seen 1.625 x 3.625. Probably won't be long until it is a 1" x 3". I feel better now. Thanks for listening.

[Will Overton]

All the current RK saws AFAIK work the same way. If you subscribe to the idea all RKs are splitters but not all splitters are RKs what you have is a low profile RK which does not support the blade guard for non-through cuts and a high profile RK which holds the blade guard for through cuts.



Great explanation.

[Leigh Betsch]

I'm still trying to figure out the problem here. My riving knife is slotted so I raise it up with a 12" blade and lower it down for a 10" blade. It's mounted in a bracket that moves it back so the arc doesn't interfere with the blade dia. It's all held on with just one bolt. Takes about 15 seconds to adjust. Overall it probably has 2" of vertical adjustment. I'm just not getting the picture how a 1/8" blade difference can be a problem. I'm feeling a little thick headed!

[Mike Henderson]

I'm still trying to figure out the problem here. My riving knife is slotted so I raise it up with a 12" blade and lower it down for a 10" blade. It's mounted in a bracket that moves it back so the arc doesn't interfere with the blade dia. It's all held on with just one bolt. Takes about 15 seconds to adjust. Overall it probably has 2" of vertical adjustment. I'm just not getting the picture how a 1/8" blade difference can be a problem. I'm feeling a little thick headed!
The SawStop saw is a 10" only saw (except for 8" dado sets). Adjusting the height of the riving knife involves a bit of work so you want to set it and forget it. I had set it for a true 10" blade. Then, when I changed the blade the riving knife was too high - because the second blade was smaller than 10".

What I did to correct this problem was to set the riving knife for the smallest blade I have. When I put a true 10" blade in, the riving knife is a bit lower than you'd like it but it works okay.

Hope that explains it. If not, ask away.

Mike

[David Helm]

I think I know what happened to the missing 1/8". When the TC inserts are welded in the saw is 10" dia. Then the TC teeth are ground and sharpened. It is like the 2" x 4" thing. A 2" x 4" is just that until it is planed 4 sides, then it becomes a 1.75 x 3.75 or recently I have seen 1.625 x 3.625. Probably won't be long until it is a 1" x 3". I feel better now. Thanks for listening.

Don't know where you get your measurements. 2 X 4s have been 1.5 X 3.5 for many decades; ever since they started planing them instead of selling rough cut.

[Leigh Betsch]

Hope that explains it. If not, ask away.
Mike

Ok I get it. The RK mounting must be quite different from my saw. Now that I think about it, my blade guard mounts to the RK so to use the blade guard I need to have the RK above the blade about a 1/2". But like I said it is very quick adjustment.

[Todd Franks]

Mike,

Thanks for the heads up. I ran a Forrest Duraline HI-AT for the first time yesterday on my Sawstop PCS. I had trouble getting the brake to adjust far enough away from the blade using the yellow plastic gauge thingy. I figured because the HI-AT cut, the effective blade diameter was bigger. I didn't realize how much bigger it was and I didn't think to check the riving knife/blade guard clearance. I just checked my blades and here are my diameters.

Forrest WWII 40T 9 15/16"
Forrest WWII Custom 20T 10 1/32"
Forrest Duraline HI-AT 80T 10 7/64"

I also checked the clearances to both the riving knife and blade guard splitter with both my smallest and largest diameter blade. The manual recommends a clearance of 4-7mm. I measured a max of 7mm with the smallest blade and minimum of 3.0mm with the largest blade on both. The blade guard clearance had more play than the riving knife. With the largest blade diameter I "wiggled" the blade guard in standby mode but could not get the red LED to trigger so I think I'll leave my settings alone for now. Something to keep in mind so I don't ruin my Duraline blade. Maybe I should get it sharpened to reduce the diameter.:rolleyes:

[Jeff Bratt]

If a blade is 25mm and stated as 10" that should make the 10" blade only .4mm or .0155" smaller in diameter, not even close to 7/8" or .125".

10" = 254 mm, so a 250mm blade will be 4 mm or .157" smaller than 10" blade - that's over 1/8" less, actually very close to 5/32".

[Jim Becker]

Since I run 10" (nominal) blades on my MiniMax slider, which is designed for 12" blades, I had to modify a riving knife to be able to drop it low enough. This involved grinding off the top of the knife, including the attachment points for the overarm guard/collector. (I have a second riving knife that retains the connection points so I can use the hood for non-through cuts) I've never measured my blades, however...