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Mitred corners sustain 42 lbs of direct pressure

42 lbs (pounds) equals 19 kilo.

At the woodworking show I made many moulded frame parts and used dovetailed splines to secure the corners.

I glued one of them back at the workshop and let it dry and then today I tried to force the joint with hand pressure. The joint held. That led me to a scientific experiment comprising nylon string, a stout vise and a 42 lb cinder block. Those of you who saw me make the splined corner will recall that I moulded the stock with a pristine ovolo profile using a 150 year old moulding plane in 12 strokes and that in under 1 minute. I then inlaid the stock of 3/4″ by 5/8″ with a mahogany inlay  and in one additional minute ran a 1/8″ x 1/8″ rabbet for glass and picture.

Today, John and I took to the test bench because of the apparent strength we saw in trying to pull the joint apart. I couldn’t break the joint by hand.

 

 

We held the ‘L’ of the frame in the vise and hung a 42 lb cinder block 1″ from the corner. It held. We moved it further along in successive steps to 3″ from the inside corner of the frame. It reluctantly broke at 3 1/8″. How amazing is that?

 

 

 

 

 

This shows the scaled weight of the cinder block. For the uninitiated, the number 3 equals 3 stones: A stone equals 14 lbs, hence 42 lbs.

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