Expansible Dowel Pins

The JUSTJOINERY® brand
Expansible Dowel Pin ®

We started manufacturing our Expansible Dowel Pin ® in 1983 to meet the needs of woodworkers. Previous to this, dowel pins had a poor reputation of being just an industrial joinery method. Dowel pins are in fact the first loose tenons and our Expansible Dowel Pins address issues with accurate sizing and joint strength that cannot be attained with either multigroove dowel pins with straight grooves or smooth pins with single grooves.

  • The ideal dowel pin to cope with stresses in cabinets, chairs, doors, windows in fact any wood product is the Expansible Dowel Pin ®
  • Manufactured in Canada from domestic hardwoods, milled .005" oversize and compressed with spiral grooves.
  • Our pins take advantage of compressed dry woods' ability to regain much of its original size with the addition of moisture. When dry wood is compressed it can be re-constituted with the addition of moisture, a technique long known by the furniture refinishing industry to remove dents. The compressed grooves are where most of this compression is released, this is where the glue resides and where most of the moisture present in the glue is available to react with the compressed wood.
  • Water based glues are not 100% solids and shrink during curing. Our pins absorb some of the glue moisture and expand to take up the space left by the shrinking glue, creating an excellent mechanical and chemical bond.
  • The spiral grooves help spread the glue across the high points of the dowel.
  • A chemical bond forms between the cured glue and wood at about .003”. Each groove forms this bond on either side of the highpoints where ever the clearance is correct, the more grooves available the more area is available to form the bond. It is most important that the dowel pin be as close to round as possible, the further out of round the pin is the smaller area available for the chemical bond to form. Our Expansible Dowel Pin ® will be slightly out of round after compression because the wood rebounds differently after compression depending on whether the grain is radial or tangential. The pin will return to its original round form during the gluing process. Not all of the compression is released, there isn’t enough moisture available and the glue cures too quickly for the grooves to return to their pre-compression size.
  • Some of the compression remains available to deal with seasonal moisture cycling.
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