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Thread: PM2000 riving knife system

  1. #1
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    PM2000 riving knife system

    Hello world!

    I am brand new to the forums (this is my first post) but I've searched a bunch and have already found tons of valuable info. So much good info that I'm getting really close to pulling the trigger on my very first table saw (I'm leaning heavily toward the PM2000 but was also considering the 1023SLX, as well as the GI and Delta hybrids at one point - but I'm really sold on the riving knife feature). There's one last question for me to ponder before I can feel 100% comfortable with my purchase-to-be. I'm new to all the TS lingo so please bear with me if my language is off... oh, and FWIW, I'm somewhat of a newbie woodworker (dad introduced me to many tools and projects as a kid but I haven't done much recently) with the expectation that woodworking will become a hobby and I'd be working on various home-improvement projects, e.g. shelving, bookcases, cabinets, basic furniture. However, I could very well decide that woodworking's not for me and end up selling the thing. Anyway, on with my question:

    I spent some time fiddling with a PM2000 at the local Woodcraft and was comparing it to the nearby SawStop. I was mainly looking at their riving knife systems. Has anyone had a chance to use the optional "low profile riving knife" on the 2000 (presumably a knife similar to the "shark fin" knife included with the SS)? I'm curious to know how well the "pivot" system works on the 2000 - particularaly in terms of how well it maintains the all-important knife-to-blade orientation - as the blade is raised/lowered. Is Powermatic's a proven system? I read that SS uses some gas strut system to achieve uniform vertical movement (no pivot). How does the new Grizzly G0605X 12" do it (watch this demo)? How do the Euro saws implement their riving knife systems? Is PM's "pivot" system considered "experimental" (like their castor system)?

    Also, reading the PM2000 manual, it appears that the knife clamp does not have a vertical adjustment (you can only tweak its lateral alignment with the blade and its horizontal proximity to the blade). The SS (AFAICT) does have a vertical adjustment. Is this a significant limitation of the PM2000? PM2000 owners, is there any way at all to adjust the knife vertically (short of tightening it down while suspending it in the clamp rather than fully seating it)? One reason I ask is because IF it turns out that this "pivot" system does a poor job at maintaining orientation (see above paragraph) you might just need that vertical adjustment capability in order to compensate for it. I'm hoping that the lack of vertical adjustibility implies that the "pivot" system works perfectly.

    Can any PM2000 owners out there comment on how well the "pivot" system works with the "low profile" knife? Can anyone shed some insight on the various riving knife systems. Which one is preferred? Which is the most robust?

    Woodcraft is going to call me this week when their shipment of 2000s comes in and I'd like to be able to tell them to put my name on one of them! Please tell me the 2000's "pivot" system is not a DUD! If it is, I might just go with a less expensive portable TS with riving knife (e.g. Bosch 4000) and upgrade to a cabinet once they figure out the technology. I'm pretty sold on having a riving knife. The more I read about and touch table saws the more I realize how all too easy it is get hurt, even if you're paying full attention! Safety has become a top criterion in my TS purchase. My guitar would sorley miss my fingers!

    Thanks in advance for replying to my first post!


    Chris

  2. #2
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    I'm not sure what you mean by the "pivot system" but I will say that I've been using the PM2000 for about four months and I've had no problems with the riving knife. Up, down, tilt all work like a champ. The riving knife is very easy to get on and off, too. I suspect it has already saved me from kickback.

    About the adjustment part of your question, I'm not clear on why you would ever need to adjust it.
    Last edited by Rob Bodenschatz; 10-02-2006 at 3:54 PM.

  3. #3
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    [quote=Rob Bodenschatz]I'm not sure what you mean by the "pivot system"

    Sorry for the poor explanation. Maybe this will help. My question was spawned from a post I read on woodnet regarding the new Grizz G0605X. It went something like this:

    From woodnet.net:
    That was my point about the end of the Uni as we know it - the present design doesn't lend itself to an easy retrofit of a riving knife that maintains it's relative vertical position to the blade. The arbor pivots around a shaft rather than translating vertically. It's not that it couldn't be done, but either the whole assembly would have to be redesigned, or a mechanism would have to be designed to work on the present arrangement (which hasn't changed in nearly 70 years)...

    The PM2000 arbor assembly is still the traditional "pivoting" style. The arbor and knife on the PM2000 don't both ride on a common, solid platform like the SS and Grizzly; but rather ride on their own platforms which appear to be connected by a couple of pivot points. SS and Grizzly, on the other hand, have replaced the pivot-style arbor with a whole new mechanism that allows the arbor (and knife) to move together vertically rather than pivot. This pretty much guarantees blade-to-knife alignment since they're both travelling up/down on the same common platform.

    In other words, PM appears to have implemented a riving knife mechanism that's compatible with the traditional pivot-style mechanism, rather than redesigning to a non-pivoting arbor like Grizz and SS have done.

    My question is whether PM's riving knife solution for the traditional pivoting arbor is actual time-tested technology or are they trying to retrofit (read: shoehorn) the knife onto the traditional pivoting arbor in "new and innovative" ways (read: unproven). Would they have been better off going with a whole redesign like SS and Grizzly? OR is PM's pivoting system possibly the same implementation that Euro saws have been using for years for attaching riving knives to traditional pivoting-arbor assemblies?

    Again, I apologize for my confusing beginner's language.

    I agree, the knife goes up , down and tilts like a champ but how does it maintain its position relative to the blade as it travels? Especially when using the low profile knife in a non-through cut where it must remain just below the top of the blade.

  4. #4
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    It stays the same distance from the blade regardless of travel. I examined it locally and was very impressed. If I did not already have a saw, I would consider this one.

  5. #5
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    OK, I just went down to the shop to see what the heck you are talking about and now I understand the "pivot". According to my eye, the knife stays a consistant distance from the blade throughout it's travels. About 1/8". I took a few pics to show the knife at two different heights. Don't know if this will be useful to you or not.

    IMG_0255.jpg
    IMG_0256.jpg

    I'm not qualified to determine which method is better. Maybe someone with more knowledge will chime in. All I know is that this cuts wood good.
    Last edited by Rob Bodenschatz; 10-02-2006 at 8:02 PM.

  6. #6
    Chris,

    I have not seen the Powermatic 2000 or the Grizzley and Saw stop riving knife mechanisms so take my comments with a "grain of salt" or maybe a salt block :-)

    Your statement:
    "My question is whether PM's riving knife solution for the traditional pivoting arbor is actual time-tested technology or are they trying to retrofit (read: shoehorn) the knife onto the traditional pivoting arbor in "new and innovative" ways (read: unproven)."
    caught my attention.

    A simple 4 bar linkage (the pivoting arbor is one link) is all that needed to insure the riving knife stays close and just below the top of the blade. In designing the "new" arbor, Powermatic or any of the other "traditional" swinging arbor saw manufacturers merely had to make a concentric bearing to hold a mount for the riving knife. That mount (with the riving knife) in turn would have a simple link back to a pivot attached to an extension to the moving trunnion assembly. By making the links equal length and parallel (the last one on the right in the image), the riving knife's geometry would be preserved throughout the blade height adjustment.

    Again, I have to say that I have not seen the Powermatic scheme. There is NOT ANY NEW TECHNOLOGY with a 4 bar linkage. Making it durable is merely a matter of making it sturdy enough. I wouldn't call that "shoehorning". A linear slider to carry the arbor is just another way of making the blade go up and down. Personally, I think it is more complicated but it does have the characteristic of keeping the blade and riving knife from "moving" back and forth. If that's an advantage, I can't see it.

    With that said, I'm working out some details of retrofitting my '70s Craftsman contractor saw with a riving knife. That's probably making the proverbial "Silk purse out of a sow's ear" but I'm poor and could use another purse :-)

    -- Teri

    [quote=Chris Setter]
    Quote Originally Posted by Rob Bodenschatz
    I'm not sure what you mean by the "pivot system"

    Sorry for the poor explanation. Maybe this will help. My question was spawned from a post I read on woodnet regarding the new Grizz G0605X. It went something like this:

    From woodnet.net:
    That was my point about the end of the Uni as we know it - the present design doesn't lend itself to an easy retrofit of a riving knife that maintains it's relative vertical position to the blade. The arbor pivots around a shaft rather than translating vertically. It's not that it couldn't be done, but either the whole assembly would have to be redesigned, or a mechanism would have to be designed to work on the present arrangement (which hasn't changed in nearly 70 years)...

    The PM2000 arbor assembly is still the traditional "pivoting" style. The arbor and knife on the PM2000 don't both ride on a common, solid platform like the SS and Grizzly; but rather ride on their own platforms which appear to be connected by a couple of pivot points. SS and Grizzly, on the other hand, have replaced the pivot-style arbor with a whole new mechanism that allows the arbor (and knife) to move together vertically rather than pivot. This pretty much guarantees blade-to-knife alignment since they're both travelling up/down on the same common platform.

    In other words, PM appears to have implemented a riving knife mechanism that's compatible with the traditional pivot-style mechanism, rather than redesigning to a non-pivoting arbor like Grizz and SS have done.

    My question is whether PM's riving knife solution for the traditional pivoting arbor is actual time-tested technology or are they trying to retrofit (read: shoehorn) the knife onto the traditional pivoting arbor in "new and innovative" ways (read: unproven). Would they have been better off going with a whole redesign like SS and Grizzly? OR is PM's pivoting system possibly the same implementation that Euro saws have been using for years for attaching riving knives to traditional pivoting-arbor assemblies?

    Again, I apologize for my confusing beginner's language.

    I agree, the knife goes up , down and tilts like a champ but how does it maintain its position relative to the blade as it travels? Especially when using the low profile knife in a non-through cut where it must remain just below the top of the blade.

  7. #7
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    Thanks for making me look stupid, Teri.

  8. #8
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    Get the Saw Stop. It is a first class machine and the safety feature is worth the extra money. There are several SS owners on this forum (I am not one as I bought a PM66 just before he SS came out) and all have high praise for them. I have seen a couple and they really look good and well built.

    CPeter

  9. #9
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    by all means strongly consider buying a saw with a riving knife. I was not aware that grizz now made a unisaw with a true riving knife.

    best wishes on your search
    lou

  10. #10
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    Rob,

    I bought a PM2000 earlier this summer. I also got the optional low profile riving knife. I have had no problems with alignment of either the standard knife or the low-profile version tho' I found the initial set up awkward and not intuitive (at least for me.)

    I did not consider the saw stop but did look at the 1023SL because of the lower price. The 12" Grizzly wasn't announced then but it is much too big for my small shop.

  11. #11
    Hi Rob,

    Sorry if I made you look stupid or you think I did. It was not my intent. I have been seeing this argument on numerous forums and feel compelled to barbecue a few sacred cows (ideas).

    Too many people are so locked into tradition without understanding the reasons. All designs are a compromise of many often conflicting forces with economics (read: lowest price) usually the winner. The riving knife seems to be slowly overcoming the lowest price argument at least on higher end equipment. It's filtering down at Grizzley and when enough people vote with their wallets, the manufacturers that refuse to upgrade will be left behind.

    I've considered making my idea for sale but the liability would be scary and I'd agonize over any accident using my gizmo even if it was due to incompetence on the user's part.

    -- Teri

    Quote Originally Posted by Rob Bodenschatz
    Thanks for making me look stupid, Teri.

  12. #12
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    Quote Originally Posted by Teri Lu
    I've considered making my idea for sale
    -- Teri
    Teri --
    I understand your concern about liability. However, I think there's a big market for a true riving knife that can be retrofitted on all the pivoting-style saws. I'd sure be interested in buying one.
    Jamie

  13. #13
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    Quote Originally Posted by Jamie Buxton
    Teri --
    I understand your concern about liability. However, I think there's a big market for a true riving knife that can be retrofitted on all the pivoting-style saws. I'd sure be interested in buying one.
    Jamie
    I would definately be interested as well. I had been informed by "experts" that it couldn't be done. I don't pretend to fully understand what you are proposing but to me it looks like it would work. If there is anything new in your design, you should at least think about applying for a patent on your idea for a retorofit Teri.

    And, oh yes I almost forget -Welcome to Saw Mill Creek Chris.
    Last edited by Frank Pellow; 10-03-2006 at 4:05 PM.

  14. #14
    Quote Originally Posted by Jamie Buxton
    Teri --
    I understand your concern about liability. However, I think there's a big market for a true riving knife that can be retrofitted on all the pivoting-style saws. I'd sure be interested in buying one.
    Jamie
    I would as well be very interested if such a beastie existed.... but like everyone else, if it works, patent it so it's not stolen...

  15. #15
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    Thanks, everyone, for taking the time to read through the long-winded, over-explanation of my question. Here's another one. Actually, my concern is all but completely alleviated, thanks to you. But allow me to give you a little more clarity on where I was coming from and what I was trying to determine. It sounds like some of you may have misinterpreted my post. It was difficult for me to articulate at first; I'm new to TS design discussions.

    My concern over PM's RK system all started after reading several posts that included phrases like "the PM's RK is cool but it's not implemented as well as SS's". I concluded that the PM RK was just not as versatile as the SS RK, and I was bummed. I wanted the 2000 but was disappointed that I would be settling for a RK that could not do non-through cuts; I'd have to remove the RK in order to perform the cut. Not a huge deal, but still... But then, after stumbling upon the "low profile" RK option, it occurred to me that the PM RM is every bit as versatile as the SS's. I was psyched!

    But soon I realized that there was a major difference between the various RK implementations (PM vs SS vs Grizz, etc.) SS and Grizz appear to have departed from the traditional pivoting arbor assm. and went with a system that seemed, to me, really well thought-out and innovative. That video I hyperlinked in my first post talked about how "on some other systems the entire trunnion system pivots on a pin up front. That means the RK is sometimes higher with relation to the blade, and sometimes lower; which can be a problem."

    Then I found the woodnet post (that I pasted in my reply - sorry I did not include the credit), talking about how difficult, and possibly impractical, it is to design a RK in a pivoting arbor system and get everything to line up correctly.

    And then I saw the 2000 at Woodcraft - without a blade, unfortunately. I saw that it had the pivoting arbor assembly. Since I could not install a blade and experiment with it at the store (I asked but the guy didn't seem very keen on the idea), I left in search of the answer to the current question, the topic of this thread: Does the PM RK suffer from this "sometimes higher, sometimes lower" nonsense? I had to find out; and the only way to find out was to join SMC and ask the community of experts!

    So.....

    1. According to you, my main concern about "sometimes higher, sometimes lower" appears to be not an issue with the 2000.

    2. My secondary question about the align-ability of the PM RK clamp remains. The manual doesn't seem to mention anything about adjusting the knife's up/down extent (say to align it 1mm below the top of the blade for a non-through cut). PM2000 owners, can you confirm that there is really no way to align this?

    3. Related question: Can anyone comment on the design of the PM's RK implementation? Is it pretty standard? Can anyone point me to related threads that may have already covered this topic this (I'm all out of keywords)?


    Rob, thanks for the pics! The pics showed me what I wanted to see. Although too bad you didn't have the low profile knife. I would like to have seen the same shots with it installed instead of the stock one.

    Teri, thanks for taking the time to enlighten me on the theory. I didn't mean to sound like I was bashing PM's design or anything; I was just trying to restate my original question. I do realize that the 4 bar linkage as a design pattern is not new technology. However, I was more interested in whether PM's implementation of it may be new and unproven or otherwise inferior to the design standard that, say, most Euro saws use.

    Andrew, thanks for the info. When you say you were impressed, were you talking by chance about the overall design of the PM2000's RK system? Do you happen to know whether this design is "standard" or perhaps similar to the design of most Euro RKs?

    CPeter, like a said above, the SS was not on my list since it was out of my price range as a hobbyist-wannabe-maybe. I do think it's worth the money though, and it's a beautiful saw. Even though some may argue that it's not as useful of a safety feature as it's touted to be, saying that most accidents are due to kickback rather than contact with the blade, isn't it also true that certain kickback scenarios could easily lead to blade contact? I could totally see myself panicking and reacting to a kickback and inadvertently putting my hand somewhere that it should not be.

    lou, I am all for the riving knife. When I look at most stock splitters these days I can see them for the clunky, hacky nuisances that they are! The Grizz saw is the G0506X and G0606X. They're both 12" saws and they're both under $2000! Too much saw for me though, I think.

    Mitchell, thanks for the added assurance. So can you confirm that the low profile knife is similar to the "shark fin" knife included with the SS? And when you installed your low profile RK for the first time, you seated it fully into the clamp and it was already set to the correct height (~1mm below the top of the blade)? Thus, no need for the ability to align the clamp up/down? I guess this makes sense but it still bothers me. Mitchell, can you tell me if you can see any way at all to adjust the RK clamp vertically? Or are you stuck with adjustment in only 2 dimensions (lateral alignment and horizontal proximity). Please don't mess up your knife alignment on my account though!

    Well, I've still got a few days before Woodcraft's shipment comes in. It looks like I'll be picking one up this week.

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