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Thread: Situations where a Riving Knife would cause problems?

  1. #31
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    So no one has tried a half fence?
    Chris

    Everything I like is either illegal, immoral or fattening

  2. #32
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    Quote Originally Posted by Chris Parks View Post
    So no one has tried a half fence?
    I have been using a half fence for 7 years and have pictures all over this forum of it in various threads. I won't run my saw without it with the exception of taking if off on the rare occasion when I cut down a sheet of ply for drawer bottoms and chest dust backs.

    And Mr. Charlie Plesums is Absolutely correct to dis-claim that a riving knife must be below the blade. I already stated that in a post before his but it needs to be said several times it appears.

    A Riving Knife is.. any form of splitter that is engineered to stay the same distance from the blade and will rise.. fall and tilt with the blade when the blade is moved. If it does this... then it is a riving knife.... period! If it doesn't then it's not a riving knife.

    I have seen around 20 different machines with riving knives both in Europe and now here. Some manufacturers make them tall to add a crown guard and some don't. Some even supply two riving knives.. one shorter for non-through cuts and one taller to use with a crown guard.

    Sarge..

  3. #33
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    Quote Originally Posted by John Thompson View Post
    I have been using a half fence for 7 years and have pictures all over this forum of it in various threads. I won't run my saw without it with the exception of taking if off on the rare occasion when I cut down a sheet of ply for drawer bottoms and chest dust backs.
    John, do you think it replaces the need for a riving knife? Since using a half fence I have had zero problems but my skill levels may have increased over that time also. I think it is something a lot of people don't like as they think it would lack support for the timber that is being cut where in fact the kerf itself supports the timber.
    Chris

    Everything I like is either illegal, immoral or fattening

  4. #34
    A half fence will not protect you from kickback caused by internal stresses in the timber being released at the cut and then closing on the rear of the blade. Whilst I can see it is an added benefit to use a half fence, I think it borders on irresponsible to advocate its use in lieu of a riving knife.

  5. #35
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    Never would I suggest that it replaces a riving knife, in fact I asked for others who have utilised one what their experience and thoughts using it were. My experience is no problems, I relate that as my experience and that only, accept that what what it is worth. Others don't think that any safety item is warranted for various reasons and I would disagree strongly, everyone has a view and we must accept the consequences of that if something goes wrong. I wonder how many people who espoused this have changed after they injured themselves, that would be a really interesting thread.
    Chris

    Everything I like is either illegal, immoral or fattening

  6. #36
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    Quote Originally Posted by Charlie Plesums View Post
    ...and is called a riving knife. But it normally extends an inch above the blade so a guard can attach to it (remember that non-through cuts are not allowed in Europe).
    Quote Originally Posted by John Thompson View Post
    And Mr. Charlie Plesums is Absolutely correct to dis-claim that a riving knife must be below the blade. I already stated that in a post before his but it needs to be said several times it appears.

    A Riving Knife is.. any form of splitter that is engineered to stay the same distance from the blade and will rise.. fall and tilt with the blade when the blade is moved. If it does this... then it is a riving knife.... period! If it doesn't then it's not a riving knife.
    In my post, which Charlie referred to, I was originally going to say "In My Opinion, If it extends above the blade then it isn't a riving knife...". But I first did some research and found the Wikipedia article, which I linked to in my post. As it supported my thoughts, I dropped the "In My Opinion" wording.

    That article states in part:
    A riving knife differs from a simple splitter in some important ways:

    • It doesn't need to be removed from the saw when cross-cutting or doing a blind (non-through) cut as it doesn't extend above the top of the saw blade. If it isn't removed, the operator can't forget to put it back on.
    Seemed pretty clear to me.

    Charlie, I did not know that non-through cuts are disallowed in Europe, and therefore the saws are engineered differently.

    I still think that "not being taller than the blade" is an important feature, as non-through cuts are one of the times that I MUST remove the splitter from my own (non-riving-knife-equipped) saw. I recognize that as being more dangerous, so I consider it an important feature for my next saw.
    Last edited by Art Mulder; 10-24-2008 at 8:49 AM. Reason: clarification.
    "It's Not About You."

  7. #37
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    Art, on the MiniMax machines that Charlie and I use, the riving knife can be below the top of the blade for non-through cuts and above it to support the over head dust collection/guard hood when it's used for through cuts. It's completely adjustable. In either case, the knife tracks with blade height and fits closely to the contour of the back of the blade. The new "north American" riving knife specifications are interesting in that they still pretty much include the clunky guard setup as a hold-over from the splitter designs of old and are not as eligant as a typical knife-attached guard from the Euro manufacturers. Of course, the best combination would be a riving knife that is just below the top of the cut and a separate overarm guard/collector...and the higher end Euro machines typically allow for that, either standard or as an option. This is something that pretty much all the Euro derived machines share regardless of brand.
    Last edited by Jim Becker; 10-24-2008 at 9:08 AM.
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    The most expensive tool is the one you buy "cheaply" and often...

  8. #38
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    I will have to dis-agree with Wikepedia on this one and back what Jim Becker said, Art. I have had two TS with riving knives and have used quite a number more before the current rage here in the U.S. If you told someone from Europe that is familiar with WW machines (as they have been required by law there since the 70's I believe) that a riving knife is not a riving knife unless it sits below the blade.. you would get a good chuckle.

    Not trying to be dis-agreeable Art... as Wikepedia is a great source of information. But.. in this case the information is only as good as the source and I do believe the source there was not very worldly traveled on Woodworking machines and especially riving knives as they are just flat out wrong in this case concerning the height.

    Sarge..

  9. #39
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    Morning Chris...

    "John, do you think it replaces the need for a riving knife? Since using a half fence I have had zero problems but my skill levels may have increased over that time also. I think it is something a lot of people don't like as they think it would lack support for the timber that is being cut where in fact the kerf itself supports the timber".
    __________________
    Chris

    ***
    Under no circumstance would I think a half fence replaces the "need" for a riving knife or splitter. And I add splitter as it does the same thing as a riving knife but a riving knife adds a small margin more as it sits in closer proximity to the back of the dangerour rear rising teeth in all positions the blade is moved too.

    There is no one item of safety that can be considered the "Holy Grail" of safety, Chris. You can only combine several items to even come close. A riving knife (or splitter) alone only keeps the kerf spread so the wood does not close and touch those rear rising teeth.

    A half fence stops no farther than mid-blade. The sever is complete on all thicknesses a 10" TS can cut before mid-blade. By not having the fence extend beyond a "free zone" is created which gaurantee's that violent reaction wood will not spread "out" and touch a long fence and then rebound back into the splitter moving it (most riving knives and splitters are made too thin and will flex from lateral force) allowing the stock to touch the rear rising teeth.

    Too go a step farther.. I use a Crown guard on top of my knife or splitter. It kick-back occurs and the wood is thrown up from the rear.. a crown guard stops it's flight. Stock will launch straight up.. up.. and away without some type top guard in that situation.

    I feel a guard of some type should be placed on the opposite side of the fence in case of kick-back to stop the stock from being hurled left. I will never stand in the lane (the direct path of the spinning blade) while the saw is running... hence the expression "Keep the Lane Clear".

    I have various widths and lenghts of home-made push sticks available and will never place my hands closer than 8" to the blade. And I will not run the saw without a shield with the exception of box joints I do with a box joint miter jig where the stock is clamped in.

    At this point do I feel I have reached the Holy Grail of safety and cannot be injured. No... Again there is no "Holy Grail" of TS safety and about the only thing that can take away the chance of amputation and bodily injury from kick-back is a Power Feeder. It it about as close to being the Holy Grail as it will get.

    Sarge..

  10. #40
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    I should have posted these pictures Chris as they seem to say a thousand words.... Open the show-thread...

    http://www.sawmillcreek.org/showpost...26&postcount=3

    Sarge..

  11. #41
    Quote Originally Posted by Daniel Hillmer View Post
    Thanks Art OK so what's the big difference safety wise, that a splitter can not do, that a riving knife can do, in terms of accident prevention?
    A splitter does NOT follow the curvature of the blade and does NOT sit close enough to the back teeth to prevent wood from contacting the back teeth of the saw allowing the saw blade to grab and throw the wood (i.e. kickback). A splitter does not move up and down with the saw blade so to avoid having it interfere with the blade it needs to be vertical with the table. This keeps any splitter from being close enough to the back teeth of the saw blade. A riving knife is attached to the saw carrige in such a way that allows it to maintain a fixed position with respect to the saw blade. This allows the riving knife to be adjusted very close to a blade. Being very close to the blade allows the riving knife to effectively reduce kickback. If the saw teeth can't grab the wood then it can't throw it at you.

  12. #42
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    Riving Knife

    I have a Felder saw/shaper with an overhead guard/dust collector attached. The riving knife is absolutely removable and adjustable. As Niki stated, I adjust mine as close to the blade as possible and slightly below it. I never have any hesitation making cuts with the ripping fence as far as saftey goes; and blind cuts are no problem either. In fact I have riving knives to match the thickness of the blades being used. I have had a Felder machines since the late 1980's and all had revovable riving knives
    The lyf so short The craft so long to lerne

  13. #43
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    I had a case that a Reaction Wood "closed" on the blade....it just stopped the blade...I'm not sure but, I think that it proves how much a riving knife that sits 1/8" behind the blade, is effective...

    Half fence (or Short fence) is not a substitute for a riving knife but additional safety feature that minimizes even more the chances for kickback.

    I've sent an E-mail to Metabo engineering department asking about the short fence...here is Metabo reply:
    -------------------------------------------
    Dear customer,

    thank you for your email regarding the setting possibilities of the rip fence.

    Reactive woods (not dead woods) can move to the side just after cutting. That´s why there might be the risk of a kick back if the rip fence is set in the long position.
    In order to minimize this it is recommended to set the end of the rip fence to the saw blade centre (short position).

    For sawing dead wood like chipboards it is recomended to set the rip fence in the long position in order to achieve the maximum guiding length.

    The riving knife is absolutely necessary and the correct position of the rip fence has to be chosen according to the wood!

    If you have further questions please feel free to contact me.
    Furthermore enjoy woodworking!

    With best regards

    -------------------------------------------
    Florian Fischer
    Produktmanager Holzbearbeitung
    Product Manager Woodworking

    Phone: +49 (0) 70 22-72-2529
    Fax: +49 (0) 70 22-72-2074
    Email: ffischer@metabo.de

    metabo
    work. don't play.
    ----------------------------------------------


    On the pictures below, you can see my case of a Reaction Wood "closing" on the blade










    The next two pictures (drawings) are from the UK HSE (Health & Safety Executive - equivalent to the USA OSHA), from a PDF file called "Circular Saw Benches - Safe Working Practices"






    As you can see, not only short fence but also High and Low fence

    You can download the file (263 KB) here
    www.hse.gov.uk/pubns/wis16.pdf

    Regards
    niki

  14. #44
    Niki,

    It's interesting the last drawing shows a bevel cut with the blade tilted TOWARD the fence. A big no-no if you have a full-length fence. Makes perfect sense with a short fence, though.
    Jason Beam
    Sacramento, CA

    beamerweb.com

  15. #45
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    Hi Jason

    You are very much correct

    With right tilt blade and long fence, the wood is trapped between the blade and the fence...

    But, with short fence, the wood is never trapped and can move free to the right side...

    If those "Safety Fanatics" (and I mean it) are showing it as safe procedure, I believe them...

    I'm doing it as "normal operating procedure"...

    Regards
    niki











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