Announcement

Collapse
No announcement yet.

Making Wood Panel Clamps

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • #31
    I think you just short circuited the process and my brain at the same time... I was rounding as I went since most of the numbers had long strings of decimals. I'll bet if I'd kept more decimal places along the way that I'd be closer to your value. Very nice Arcane... very nice... And best of all it makes sense instead of all my go arounds that apparently cancel out and would likely simplify to your method.
    Chilliwack BC, Canada

    Comment


    • #32
      The formula is interesting and I have made some notes for future use.
      So assuming these figures are pretty accurate or at least close, how is the thread surface factored in? I'm guessing these formulas are based on clean and oiled threads? Am I correct?
      We all know what wood working clamp screws end up looking like from sitting around for years, especially if they are not cad plated or chromed. Screws that are dry with a light coating of surface rust are going to require more force to turn. I don't have that problem in my shop and I do keep all my clamp screws clean and lightly oiled. Can't over do the oil because of the dust situation.

      So back to my original question. Is it possible to develop 7000 Lbs of clamping for with a 5/8" - 6 ACME screw mounted in the center of a 5 1/2" long handle without using both hands and everything you got to tighten it down? I'm guessing no since I've seen other clamps with the same screw pitch and handle size / length and some even longer claim clamping forces of around 1700 Lbs. That seems more reasonable and a force that the entire clamp can with stand.
      With the Jorgensen bar clamps and their advertised force of 7000 Lbs. seems unrealistic and as I said I doubt the cast heads would hold up. That may be the maximum amount of force that can be developed by the screw with X amount of tightening force but not what the entire clamp can withstand. Advertising point I would imagine. And there is such a thing as over stressing a glue joint.
      I usually tighten mine with one hand using my thumb and fore finger to turn the handle. That is more than enough force to squeeze the glue out of any joint. I have no clue as to how much clamping force that is but It's no where near 7000 Lbs.
      I suppose simple way to get an idea would be to get a good heavy spring, like a valve spring from an engine or something where you know how much force it takes to compress it and put it in the clamp and get a feel for how much force it takes.

      JL................
      Last edited by JoeLee; 02-23-2020, 09:35 AM.

      Comment


      • #33
        Originally posted by JoeLee View Post
        ...If you have plenty of thickness to plane away then any unevenness is a non issue but when your working with boards that are close to finish thickness there is no room for error and most of the time I don't have enough hands to put all these clamps to work as the glue is setting.
        All of my glue-ups have been with finished sized lumber. I also work alone. These panels for the sides of a Murphy bed I made a couple of years ago are about 7 feet by 18 inches, so there are about 3 or 4 sticks in each. My technique gets the panels flat, because anything else is unacceptable. All the floating panels in the bed were also multi-board glue-ups, too. I don't use clipped nails, biscuits, salt or sugar in any of my panel glue-ups. If I am concerned about wavy boards, I'll use dowels in conjunction with a doweling jig to align the boards.

        Click image for larger version

Name:	DSCI0443.JPG
Views:	59
Size:	708.5 KB
ID:	1857182

        This was the goal of all the glue-ups.

        Click image for larger version

Name:	MB_Closed.JPG
Views:	61
Size:	750.7 KB
ID:	1857184

        The below panel was by far the most difficult glue-up I have ever done. The result was a square, flat panel about 80" by 60". All the rails and styles are constructed with floating tendons, which added to the difficulty. It was accomplished using regular HF ¾" pipe clamps and black pipes (with sometimes added couplers to make the length I needed).

        Click image for larger version

Name:	DSCI0457.JPG
Views:	61
Size:	822.6 KB
ID:	1857186
        Attached Files

        Comment


        • #34
          There was a write up in Wood magazine years ago about the same concept as the first clamps you linked to, but with the majority of the system made out of wood, only the links and screws were made out of steel and that was common perforated flatbar and threaded rod couplers.

          The only thing time consuming about building the clampzilla model would be the links. That is something I would farm out to either a laser shop or a water jet shop and get done in mass.

          All that said, I have glued up a lot of wood panels over the years and tried all sorts of schemes to make clamping easier. Then it dawned on me, spending a little more time in stock preparation, would save me a ton of time during glue up and finishing. So I tuned up my jointer and got much better at making things straight and flat.

          Clamp companies spout numbers about clamping force, high clamping force is meaningless in wood working. After all what is tensile and compression strength of the materials and glue being used? We aren't working Titanium after all.

          Having gone down the bar clamp rabbit hole myself, what I eventually ended up doing was just buying a couple dozen new Pony clamps and making the bars out of Sch80 Aluminum pipe. No rust, no fuss, light weight and plenty strong.
          I just need one more tool,just one!

          Comment


          • #35
            Originally posted by JoeLee View Post
            ............So back to my original question. Is it possible to develop 7000 Lbs of clamping for with a 5/8" - 6 ACME screw mounted in the center of a 5 1/2" long handle without using both hands and everything you got to tighten it down?...........
            No, as you surmised, not even close. From https://www.hexagon.de/rs/engineerin...ndamentals.pdf

            The torque applied to a fastener is absorbed in three main areas. First, there is underhead friction, which may absorb 50 percent or more of the total torque. Thread friction absorbs as much as 40 percent of the applied torque. The final 10 percent of the applied torque develops the clamping force that holds the components together. Thus an increase in either friction component of 5% can reduce tension by half.
            Location: Saskatoon, Saskatchewan, Canada

            Comment


            • #36
              I'm not so sure.... We've all seen some really butchered stretched out "C" clamps in metal and welding shops. It least I know I have. And that's only the bent ones. The ones that snapped got tossed out. What's it take to butcher those?

              Is 9000'ish or even 7000'ish possible? I'd say no too. But it would not shock me at all if we found that we could generate well over 2000 lbs with that handle and that screw.

              Which might well be why F clamps primarily come with just screwdriver style wood or plastic handles. And consider how easy it is to curve the bar on those.
              Chilliwack BC, Canada

              Comment


              • #37
                Originally posted by Arcane View Post

                No, as you surmised, not even close. From https://www.hexagon.de/rs/engineerin...ndamentals.pdf


                Well, then I guess it is false advertising on the part of Jorgensen. I wonder how many people fall for that ? I would think that the internal cast threads on the fixed head would strip out long before the force reached 7000 Lbs.

                JL.....................

                Comment


                • #38
                  Originally posted by BCRider View Post
                  I'm not so sure.... We've all seen some really butchered stretched out "C" clamps in metal and welding shops. It least I know I have. And that's only the bent ones. The ones that snapped got tossed out. What's it take to butcher those?

                  Is 9000'ish or even 7000'ish possible? I'd say no too. But it would not shock me at all if we found that we could generate well over 2000 lbs with that handle and that screw.

                  Which might well be why F clamps primarily come with just screwdriver style wood or plastic handles. And consider how easy it is to curve the bar on those.
                  C- clamps are an entirely different story as most are very soft and it doesn't take much force to spread them. Unless you get the good Wilton forged clamps which take a bit more stress.

                  JL..............

                  Comment

                  Working...
                  X