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Thread: Delta 34-350 12-14" riving knife retrofit

  1. #1
    Join Date
    Oct 2007
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    Davisburg, Mi.
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    27

    Delta 34-350 12-14" riving knife retrofit

    Hi All,

    After using a friends saw with a riving knife, I thought it a good idea to add one to my 34-350.

    Ihave attached photos of a test fit last night, not a bad fit-up for something made from dimensions written on the back of a pulley box.

    As most all of you know who have thought about riving knife retrofits on a saw with an arbor configuration such as the Unisaw, the motion is in an arc and the riving knife does not maintain the correct relative position through the arc. my original design used a 4bar link system but i settled in this one because the linear motion on the rear bearing block makes a perfect spot to mount the scale for a remote readout for blade height. (Wixey or others). another motivating factor is that this saw mounts 10,14,14" in blades and i need a bit of flexibility with knife mounting.

    I will make this first post a bit brief (running a bit late for work) I will add details later this evening but so far everything is extremely rigid and works well, the mount for the knife will be on the square block.

    here are some photos;cheers,
    Sean

    P.S.
    Yes, the saw is getting a micro-v belt in the deal also.






    UP



    and Down...same relative position...Yippee!

    Last edited by Sean lennon; 02-18-2010 at 7:19 AM. Reason: typo

  2. #2
    Join Date
    Jul 2007
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    Seattle, WA
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    That is some seriously impressive fabrication. Wow!

    If you get this thing to work well, you should consider marketing it.

  3. #3
    Join Date
    Oct 2007
    Location
    Davisburg, Mi.
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    Thanks Peter,
    I re-assembled the machine tonight and made some repeatability measurements with regards to the platform tracking the actual blade position.
    I am regularly getting .003-.005 with static and .003 with the blade running.
    the bearing trucks have a bit of preload stiction that is overcome with the slight vibration the machine has while running and there are parts for the structure that I know are deflecting, namely the bar that connects the arbor bearing to the carriage. in the big picture, I don't know how much this really matters anyways and I am going to use it awhile before I pass judgment.

    The knife mounting is very rigid and is further enhanced by support from the zero clearance insert on the saw. the knife is made from hard stainless in two thicknesses .125 and .10 I am sure the .10 will spend most of the time mounted as I use the saw mostly with the 10" blade mounted.

    I stopped by a friend today that has a unisaw and the design scales very well for that machine also. infact, he has convinced me to make a 10" uni version for his saw.

    I am painting the parts, will post photos when they are dry and mounted on the machine


    cheers,
    sean

  4. #4
    Join Date
    Oct 2007
    Location
    Davisburg, Mi.
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    27
    Added a 6" linear scale to the assembly for a digital height readout this evening.

    I am currently in the process of making a couple of riving knifes for the 10" and 12" blades.




  5. #5
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    Cache Valley, Utah
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    Very nice job. Looking forward to seeing it with the knife installed. A video would be great, too.

    I would be interested in a Uni and a 12/14 setup (without any digital stuff) if you ever decide to go into production.

  6. #6
    Join Date
    Jun 2007
    Location
    Half Moon Bay, CA
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    I'd be interested in one for an older uni, with or without the digital readout.

    Seriously cool.
    >witty woodworking quote goes here<

  7. #7
    Join Date
    Oct 2007
    Location
    Davisburg, Mi.
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    27
    I mounted a knife mock-up and am getting things mounted.

    slowly but surely...

    And VIDEOS (my first youtube post so go easy)

    http://www.youtube.com/watch?v=we0dRqf4ceU

    http://www.youtube.com/watch?v=n6sggfC0HOQ

    http://www.youtube.com/watch?v=Q8hNK2tQtmE



    you are going to say "the bolt is off center"...yes it is, there is a method to my madness, I will show you later.

    My apologies if this is of little interest; i know 12-14 Deltas are not the norm but it makes a good testbed AND it is what I have.


    cheers,
    sean




  8. #8
    Join Date
    Mar 2006
    Location
    Kingston, Ontario
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    390
    Wow!!!

    It only goes to show there are some clever people out there.

    Delta has a bunch of design folks and they have not so far been able to come up with a retro fit for the thousands of Unisaw out there.

    If you go into product for a 10 inch Unisaw count me in.

    Keep up the good work.

    Greg

  9. #9
    Hi: Beautiful design and implementation. I made a retrofit riving knife for a Delta contractor saw recently, but I took the approach of using whatever caught my eye as I was shopping at OSH. In addition, rather than trying to track the arc of the saw arbor's motion, I approximated it's motion by slanting my bearing rod, figuring that the riving knife would deviate from the arbor by only a fraction of an inch and concentrated on tracking the up-down motion of the arbor.

    I have a few questions. I'm not interested in selling or marketing any products, but as a hobbyist, I'm always hoping to improve my own design.

    I am curious as to what linear bearings you used in your design and what their tolerances are, especially for rotation around the direction of travel. Also did you find that using two bearings at right angles create increased resistance to the travel of the riving knife support (relative to each bearing alone)?

    In additional, if you don't mind revealing your construction, what are the details of the follower on the arbor? Is that mounted on a bearing(s)? I would have some apprehension at disassembling the arbor at the risk of breaking the cast iron parts. In my case, I targeted a retrofit which did not require an extensive disassembly of the saw.

    Anyway, thanks for this very interesting post. I realize that unless you've actually designed and made one of these things, it's hard to understand how much effort it takes to get to a finished, installed, product.

  10. #10
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    Toronto Ontario
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    Sean, very ingenious, I'm impressed.........Regards, Rod.

  11. #11
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    Great clips, thanks for posting. If you haven't already done so, you might also want to go over to OWWM and after you get a feel for the place, post your info there, too.

  12. #12
    Quote Originally Posted by Dave Cav View Post
    Very nice job. Looking forward to seeing it with the knife installed. A video would be great, too.

    I would be interested in a Uni and a 12/14 setup (without any digital stuff) if you ever decide to go into production.
    Check out walnutacrewoodworking.

  13. Great work, very thought out. The only thing i'd suggest is a radius on the the bottom of the riving knife; in case the wood binds on the knife and as you push you loosen the allen head screw, which would rotate the knife into the blade. Or maybe a second allen head to secure the riving knife.

    -tyler

  14. #14
    Join Date
    Oct 2007
    Location
    Davisburg, Mi.
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    27

    Q&a

    Howdy again,

    hope to answer some questions,

    Floyd,
    the bearings are THK SHS15LM series units with preload.
    they are a good compromise in size, cost, precision and rigidity, especially when used with the preload option. there is also an optional heavy contamination wiper assembly visible in the photos as the large black plastic endcap. as to how rigid they are...perhaps 4 times more than a standard off-the-shelf unit without the preload. I can send you numbers in kN but that doesn't always tell the entire story from a bearing performance standpoint. for this application they feel really rigid but roll quite easy.

    As for 2 bearings at right angles, as long as rigidity is controlled; 2 axis coupled motion is not a problem...But...the structure MUST be rigid otherwise it will try to twist and distort all over the place.

    The arbor follower is a deep groove bearing inside the housing(sealed) that is pressed onto a sleeve that I machined to fit the arbor (FYI: it is 15/16...not a common bore size for a bearing).
    the common datum for the saw is the arbor axis, so, why not use it? besides; picking up a location elsewhere leads to kinda messed up kinematics of the system. pulling the arbor is no big deal, 30 minutes max once the table is off. is breaking arbor carrier castings commonplace on the Uni? The 34-350 is a tank, I can't imagine breaking that casting


    Tyler,
    I understand your concern for the knife mounting.

    The knife you see in the photo is a piece of .053 aluminum that i hacked a mock-up of with a pair of tin-snips for general size and shape.
    the actual blade retention system consists of a cassette that has 2 steel pins on either side of the large bolt you see in the photo. what is not in the photo is the steel cover-plate that captures the 2 dowel pins and sandwiches the blade between the cover plate and the base plate, not a lot of opportunity for movement of the knife once mounted.
    the baseplate is adjustable for minor trimming of the blade alignment by setscrew.
    This entire blade carrier I just described is asymmetric such that by removing 4 mounting screws and flipping the blade carrier; it aligns with a 10" blade mounted on the 5/8 arbor for the saw(new knife required though)
    That is the primary reason the bolt is slightly offset

    For the knifes I will be using 1/2 Hard, 301 stainless ground-polished.


    hope that answers the questions for now

    cheers,
    sean
    Last edited by Sean lennon; 03-06-2010 at 7:02 AM.

  15. #15
    Join Date
    Oct 2007
    Location
    Davisburg, Mi.
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    27
    Carrier and 12" riving knife are now complete.
    the plate can be flipped to accommodate a 10" blade.
    the 2 bolt heads locate the knife and are captured by the clamp plate shown in the last photo.

    now...on to the 10" knife!


    cheers,
    Sean






    The wing nut is a bit big but it is what I had until I come up with something better.

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