Coffman Clamps – Getting Square Corners

Sourced from MRHMAG.COM by Jack Burgess

Many resin freight car kits sold today feature one-piece bodies which greatly simplify their assembly. However, many models are still flat kits – a kit containing a set of flat panels. Some of us still have large stashes of unbuilt flat kits. It is critical that the sides and ends are square and properly aligned with each other when building a flat kit. That task is greatly simplified by using an Original Right Clamp produced by Coffman Graphic Solutions. Although also available from Micro-Mark, I bought mine directly from Coffman (















Figure 1: The Original Right Clamp is perfect for resin freight car assembly. A piece of aluminum angle ensures 90º corners while foam on the clamp faces protects fragile details when clamping parts together. Coffman makes longer right clamps for structures.










Figure 2: To use the clamp, first position the clamp with the edge of the resin side of the car about even with the face of the opposite clamp.










Figure 3: Then lightly clamp the end in place. Both clamps should be tight enough to hold the pieces in place, but loose enough so the parts can be wiggled into final position.










Figure 4: Move the side and end pieces until they are in proper alignment to each other and the joint is tight without a gap. Then tighten the clamps as needed.











Figure 5: This is what the inside of the clamp looks like with the parts in proper alignment










Figure 6: Test fit the roof before bonding the side and end together to make sure the parts are in correct alignment. With some kits, the tops of the pieces are even while other kits are designed with the bottoms even.











Figure 7: Apply cyanoacrylate glue in the space between the clamps. Hold the assembly level or slightly “downhill” to eliminate migration of the glue under the clamp. I use a super thin  cyanoacrylate marketed under the Zap brand name from Pacer Industries which includes aTeflon tube making it easy to apply the glue directly to the joint.











Figure 8: I use a small jar to hold a little cyanoacrylate accelerator such as Zip Kicker, also sold under the Zap brand name. Accelerators are universal and will work with any brand of cyanoacrylate. The accelerator instantly sets the cyanoacrylate, keeping the glue from migrating. I apply the accelerator to the unset cyanoacrylate with a Microbrush – available at hobby shops or through Micro-Mark. A single brush will last for several kits. Dip the brush in the accelerator and quickly run it the length of the joint so that the brush isn’t glued to the joint. As soon as the glue dries, unclamp the parts and finish the joint by applying glue to the area that was behind the clamp.





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  1. Peter
    3 months ago

    The SHARE thingy that shows up on the webpages and won’t go away is really annoying. It covers up a big piece of the page on the left side of the screen. I cannot read what is behind it. It stays there even when scrolling.

    • normal
      3 months ago

      Hi, what is your screen resolution?