Sizing

Dowel Pin Sizing

  • The dowel pin should be the same size as the drill used to make the hole. It is normal to use clamp pressure or a dead blow hammer to assemble a joint. In a properly fitted joint 2 to 3 dowel pins per joint is normal.
  • The type of drill, type of wood and condition of the drill cutting edge will all produce a different size hole. An inexpensive 3/8” drill can measure .368” and a quality drill .375”. Purchase quality drills, to be sure, measure the drill with a vernier or micrometer and find one that is as close as possible to the dowel pin size you are using.
  • Testing with different drills and glues can provide a different fit.
  • If you find your joints too tight, our Expansible Dowel Pins can shrink about .002” by putting them in a warm oven at 200°F or 93°C for 20 minutes on a clean cookie sheet. Warm the oven then shut it off before putting the pins in.
  • It is normal practice for industry to use dowel pins that are a much tighter fit than most woodworkers would prefer. Some manufactures use pneumatic or hydraulic clamps to assemble joints. They use the friction fit to hold the joint together while being able to remove it from the clamps quickly. Using dowel pins that are too large risks splitting the wood.
  • Seasonal cycling affects joints; the wood around the joint will compress the pin during humid cycles then pull away from the pin during dry cycles causing the joint to loosen. With Expansible Dowel Pins not all of the compression is released while the glue cures leaving some compression to help keep the joint together during cycling.

Length

  • Another aspect to sizing is pin length, so how long should a dowel pin be?
  • The main issue to consider is grain direction. If the grain direction of the dowel pin is at 90° to the wood then the pin should be as short as possible. The issue is again seasonal cycling. Tangential and radial expansion rates are quite often very different and the resulting expansion and contraction differences between the wood and the dowel pin can cause the joint fail.
  • More short pins are more effective than a couple of long ones, the surface area can be maintained and the sheer strength increased.
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