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Thread: Hold Down Clamp Material

  1. #1

    Question Hold Down Clamp Material

    I tried to re-pupose an old oak table top and make some clamps and V-blocks for my CNC router.

    Maybe the wood was too dry, the PVA glue too brittle, the grain direction wrong. I can't say for sure I'm a novice at this stuff.

    What material/species do you use for DIY hold downs. What should I look out for in terms of grain orientation?
    Last edited by John K Jordan; 08-24-2020 at 6:34 PM. Reason: fuxed typo in title

  2. #2
    I use Maple, Anthony. A couple of them are Walnut but most are Maple. I haven't broken one yet and just pick up some small leftover pieces from other jobs so I don't pay much attention to the grain direction. It's long with the clamp and not cross grain, fwiw.

    David
    David
    CurlyWoodShop on Etsy, David Falkner on YouTube, difalkner on Instagram

  3. #3
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    I use scrap oak strip flooring material for hold-down clamps successfully. The Oak is "springy". I make the grain orientation lengthwise, and cut a recess that allows about .125" of material on top of the workpiece. This things have been VERY durable.
    --

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

  4. #4
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    I use aluminum.
    Glad its my shop I am responsible for - I only have to make me happy.

  5. #5
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    Last edited by David Buchhauser; 09-13-2020 at 3:13 AM.

  6. #6
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    David I take it you've never had a crash into one of those steel holds? I had one on my aluminum ones and it was just like... milling aluminum for a short time!!
    Retired Guy- Central Iowa. , LightObject 40w CO2 Laser and Chiller , WorkBee 1000x750 CNC Router - Mach4 - Windows 10

  7. #7
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    Quote Originally Posted by Bill George View Post
    David I take it you've never had a crash into one of those steel holds? I had one on my aluminum ones and it was just like... milling aluminum for a short time!!
    I was thinking the same thing...I’m even switching to nylon bolts for my wood clamps!
    --

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

  8. #8
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    1/8" x 1" aluminum strapping about 4 inches long with hole in the middle for the 1/4 bolt in the "T" track. Ends are bent slightly so it sits on the piece a bit better. 7/16"wrench lives on my spoil board. Have cut a few of them will no apparent ill effects...

    I have different lengths of bolts for different thicknesses of wood. If it's tall I'll put a spacer block under the outside edge to keep it as level as possible.
    Funny, I don't remember being absent minded...

  9. #9
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    Quote Originally Posted by Bill George View Post
    David I take it you've never had a crash into one of those steel holds? I had one on my aluminum ones and it was just like... milling aluminum for a short time!!

    No - I never have. Just like I do with my cnc milling machine, I do a test run with slow feed rates and the tool heights offset about 2 or 3 inches above the work piece just to make sure there won't be any interference problems. I have caught several problems on the cnc mill (machining center) and made adjustments before doing the actual cutting. Same for the cnc lathe. We call it doing a "dry run".
    David

  10. #10
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    With all those tools you think you could make some aluminum clamps.
    Glad its my shop I am responsible for - I only have to make me happy.

  11. #11
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    Quote Originally Posted by Mike Heidrick View Post
    With all those tools you think you could make some aluminum clamps.

    I could, but why bother when what I have works for me.
    David

  12. #12
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    I use 3/4" thick PVC scraps, cut them to fit on my band saw. I get perfect tension without the worry of the material splitting and its so soft if a router bit hits it there is not any issue. We have discussed this issue in several threads, search our archives for more information.

  13. #13
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    Ever since having a small incident with a 1/2" piece of aluminum I very rarely have anything like that on my table. The thought of $6k for a new spindle insert was a scare. I like plastic scraps as well.

  14. #14
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    I have several I made several years ago and also use some of the Rockler ones. Also use some of the Rockler stops in the t-track to position stock (keeping it from sliding around is as important as holding it down). All aluminum. Have some leftover solid hickory flooring strips that I will use to make more. Eventually.
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    Colorado Woodworkers Guild
    Colorado CNC User Group

  15. #15
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    How can you beat PVC clamps. They are dirt cheap, you can make dozens from just one PVC board that you purchase from a local store. Nothing is even close to your router bit except the soft PVC material. It will never split and it holds as tight as any other clamping method. Its easy to make custom hold downs to fit most jobs in a few minutes if you own a band saw. I use wood screws but you can use knobs, machine screws and track components just as easy. I have never had any project move at all using this technique.

    You own a CNC Router so its easy to machine these yourself, cut them from the bottom and instead of holes machine a slot so you can adjust the tension at more locations. You can even shape the ends to fit into almost any configuration if a custom hold down is necessary. You can see that a router bit hit one of my PVC clamps, it didn't cause any problems and I still use that clamp.
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    Last edited by Keith Outten; 09-16-2020 at 11:37 AM.

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