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Thread: New Sled

  1. #16
    Join Date
    Feb 2009
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    Cedar Park, TX - Boulder Creek, CA
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    832
    Quote Originally Posted by Dan Cameron View Post
    This configuration has ZERO precision or stability advantage over a similarly fitted single runner. That is, if there is .005" of side to side play, it makes NO difference if the two guiding edges are .75" or 10" apart. (unless your runners are sponge rubber)

    My gut feeling on this is that it's only true in terms of lateral displacement. But the wider the spacing the greater the angular error. So I modeled it up to see.

    It's true, the wider the runner spacing, the greater the angular error. However, with any reasonable length of runner, like 12", the error is 5 decimals out ;-)

    The bigger issue *could* be racking and binding. But again, unless you're trying to use 3" long runners in slots spaced a foot apart, I doubt it's going to be noticeable. Differential expansion from heat or moisture is the only thing to worry about.

  2. #17
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    May 2014
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    Alberta
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    I think you guys just need to buy a slider....

  3. #18
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    Mar 2006
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    Quote Originally Posted by Mike Kees View Post
    I think you guys just need to buy a slider....
    Too true. I didn't know single versus double was so controversial. Use the method that works for you and be happy.
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  4. #19
    Join Date
    Mar 2003
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    SE PA - Central Bucks County
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    Quote Originally Posted by Mike Kees View Post
    I think you guys just need to buy a slider....
    Funny you should mention that...

    While I've been "making do" with a very nice cabinet saw in the temporary shop, I did order a replacement slider this past week that should arrive a few weeks after the building is up. I have missed it "big time".

    Glenn, I'm in the two runner camp but I can certainly see the other point of view. So far, my quick and dirty sled is working without binding, but it will be interesting to see if that continues as the humidity builds even more in my unconditioned temporary "gara-shop".
    --

    The most expensive tool is the one you buy "cheaply" and often...

  5. #20
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    Quote Originally Posted by Jim Becker View Post
    . . . my unconditioned temporary "gara-shop".
    Let's have some respect for the temporary digs . . . "Garag-Mahal" if you please.
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  6. #21
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    Mar 2003
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    SE PA - Central Bucks County
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    Quote Originally Posted by glenn bradley View Post
    Let's have some respect for the temporary digs . . . "Garag-Mahal" if you please.
    Just. because I (mostly) put a fresh coat of paint on it does not a 'Garage-Mahal" make. But I appreciate the thought. I'm very thankful I have the space I have, however. It's not adequate for big work, but I can do the smaller projects that come up if need be. It's just horribly uncomfortable with the heat and humidity in full swing right now.
    --

    The most expensive tool is the one you buy "cheaply" and often...

  7. #22
    Join Date
    Oct 2015
    Location
    Melbourne, Australia
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    153
    Every time I make a matchfit sled like Glenn's it sags slightly in both directions. I'm sure that's due to the large amount of material removed when routing so many slots. That's one advantage of T Track. I've tried 15mm and 18mm MDF and 18mm ply. Do I simply go for a thicker board eg 25mm (about an 1") or is there something I'm missing.
    Does you see any sag on your sled Glenn?

  8. #23
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    Quote Originally Posted by Johnny Barr View Post
    Does you see any sag on your sled Glenn?
    These two actually had a tendency to cup. It took a few days to get around to adding the fences and by that time they had settled down. I attributed this to the stock removal and the weather damaged ply. My experience with good BB ply for previous sleds is that if it starts out flat it pretty much stays that way for years . . . unless the sled gets wet but that's another story for another time . 3/4" MDF with the grid pattern cut in could become pretty flexible. The bulk of the sled is supported during use so this may not be a problem in use(?). Cutting a 3/8" deep dovetail in 15mm ply doesn't leave much behind so 18mm would be my choice.
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

  9. #24
    Quote Originally Posted by glenn bradley View Post
    These two actually had a tendency to cup. It took a few days to get around to adding the fences and by that time they had settled down. I attributed this to the stock removal and the weather damaged ply. My experience with good BB ply for previous sleds is that if it starts out flat it pretty much stays that way for years . . . unless the sled gets wet but that's another story for another time . 3/4" MDF with the grid pattern cut in could become pretty flexible. The bulk of the sled is supported during use so this may not be a problem in use(?). Cutting a 3/8" deep dovetail in 15mm ply doesn't leave much behind so 18mm would be my choice.
    My sleds have also tended to stay flat even with the humidity swings I have experienced. I have been careful to use the same material for my fences as the sled base (e.g. plywood/plywood) lest differential expansion and contraction cause warping. Also, I have not cut groves for tracks. If I need a hold-down or miter guide I just screw it to the base. After many years I have an ugly sled (from screw holes) which works just as well as the day built.

  10. #25
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    Quote Originally Posted by Dan Cameron View Post
    After many years I have an ugly sled (from screw holes) which works just as well as the day built.
    The VERY best kind IMHO
    "A hen is only an egg's way of making another egg".


    – Samuel Butler

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