Clamping pressure vs glue strength

[Steve1]

Very informative and useful test.

But the one thing that surprised me was that all (I think) samples failed at the glue.
Particularly with a low strength wood like pine, I would have expected to see a lot of ripped of wood, where the parent material failed before the adhesive.

 

[usernumber1]

now i want to know how strong would the glue be at different thicknesses. so a test with metal blocks glued with pva and clamped at different pressures. or would they all break same because they stick with the same force on the metal surface which is less than shear break force of the glue?

 

[Michael Kellough]

Think the most useful testing would be with different surface characteristics of the wood.
Sanded with a broad range of grits and including some hand and machine planed surfaces.

 

[Packard]

Think the most useful testing would be with different surface characteristics of the wood.
Sanded with a broad range of grits and including some hand and machine planed surfaces.

An issue with testing sanded surfaces, not only does the sander affect the surface texture, it can also affect flatness.  I doubt that any random oscillating sander will produce a totally flat surface.

Fletcher-Terry makes a dedicated 45 degree angle sander for dressing already mitered joints.  They use PSA to adhere the sand paper directly to a metal disc.  Hook and loop fasteners allow too much movement on the surface.
https://www.fletcher-terry.com/frame-joining-material-cutting-products-1/amp-disc-sander