That conversation with a trim carpenter about sanding changed my thinking

I was on a job site in Portland last Thursday installing some built-ins when a guy named Dave stopped by and said I was over-sanding my edges before glue-up. He told me to just rough up the surfaces and let the glue do its job, said sanding too fine actually makes joints weaker. Has anyone else run tests on how grit level affects joint strength on maple?

2 comments

2 Comments

the_ruby24d ago

Oh yeah Dave's got it right. I tested this a couple years ago on some walnut and maple scraps I had lying around. Did 60 grit, 120 grit, and then 220 grit on separate pieces before gluing them up with Titebond 2. The 60 grit joints actually held better when I broke them apart than the 220 grit ones. Like the glue just kind of sat on top of the super smooth surface instead of getting into the wood fibers. Now I just hit everything with 80 or 100 grit before glue up and honestly my joints feel way more solid. It feels weird at first cause you think smoother is better but it totally makes sense once you see it.

daniel55224d ago

Man I had a buddy who did basically the same experiment but on accident. He was building a dining table for his sister and sanded everything down to like 400 grit cause he wanted it super smooth before glue up. A few months later the legs started coming loose and he had to redo the whole joinery. He told me when he chiseled the old glue off it was literally just sitting there in a sheet like a sticker. Now he hits everything with 80 grit and tells everyone the same thing. Funny how we all have to learn that lesson the hard way.