MachTwang

Excellent, Thank you so very much for the advice.

You are correct! It should have been 0.65mm. This is a Martin uke that is about 100 years old, the cracks run from the upper bout to the first brace and they do not require any force to get them to meet and I can see no light through them. So you are saying that for these kinds of cracks all I would need to to blow some glue in?

I am currently working on an old Martin ukulele with two cracks in the back and as I was crafting some cleats out of Mahogany I got to wondering how thin is too thin for a cleat? I have some mahogany veneer that is .065mm thick and as you can see in the photo I have cut it 20mm long with the grain and 5mm wide, my thought was to lay them across the crack at the beginning, middle and end almost like sutures. How this in too thin for a cleat? What are your thoughts?