Testing

  • Testing the ability of the joinery components to withstand withdrawal is the goal. The method consists of holes drilled through Hard Maple with dowels or tenons glued in place so that some of the pin or tenon protrudes above the wood. This assembly is set aside to let the glue cure and for the moisture to dissipate.

  • The assembly would be placed on a recording load cell so that the pin or tenon can be pushed through with pressure applied in a continuous motion until the joint fails. This pressure is recorded by an electronic recorder eliminating any inaccuracies of trying to see a pressure gauge at the point of failure.
  • Shear testing should be accomplished in a metal jig so that the materials used as the mortise cannot affect the actual pressure required to shear the tenon or pin. The recording load cell is used to record the result.

  • Another issue is testing multiple elements and in most cases comparing joints that don’t have equal surface areas. Testing one dowel or tenon at a time and then calculating surface area is the only way to get a true measure of each component.
  • Using woods like Cherry to create joints usually tests the strength of the wood and not the joint
  • Testing a joint made with a wood that isn’t as strong as the joinery elements and then subjecting that joint to stress by deflecting the joint away from 90 degrees proves nothing. An accurate picture of joint quality isn’t possible unless joint strength, sheer and the wood used to make the joint can be separated.
  • Tearing a joint apart using a bottle jack confuses, withdrawal, sheer, the strength of the wood used for all parts of the joint. Using anything other than a recording load cell will not accurately record anything, pressure gauges and bathroom scales cannot be relied upon to give accurate or reliable results.
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