I will often use a wasteblock glued to a bowl blank to maximize the depth I can get out of a blank. I have had good success using Titebond II to attach the wasteblock to the bowl blank. For "clamping" I have always used a couple of square rubber coated 5 pound weights that stack, followed by a block of wood followed by some cinder bricks. Maybe 30-40 lbs of weight total. Never had any problems. Joints always seem really good, with nice glue squeeze out (I make sure that the surfaces are very flat). I know some people use double sided tape, paper joints, and hot glue...so I figured I was being pretty safe with this method.
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I was reading the Titebond II information sheets recently and they recommend 150 psi??!! So with a 6" round waste block with an area of about 28 square inches, I would need 4200 pounds of clamping force?? Which would require several medium duty woodworking clamps at close to max force. I must be misunderstanding something here.
Would appreciate your thoughts including any perspectives on my clamping method. Just because I haven't had any problems doesn't mean it's safe.
Thanks,
-Dan