Sanding grit for smooth-on

[Mad Max]

For fiberglass to wood.   I use 60 grit because that is what I have
What is the finest grit you can use for smooth-on?

[fujimo]

mark i have used 120 grit on my two kenny m bows that i have built- cos thats what i had- and they're still going well- but the standard seems to be 60 and have even heard of some using 36

[Bowjunkie]

I have used 36, and it's about as coarse as the grooves my toothing plane leaves behind, and I think that they are a near perfect combo.(toothing plane grooves and Smooth On). Even in highly stressed, working, fade-to-nothing glue joints in the dips of say a tri-lam, they don't fail. For use under clear glass however, grooves left by 36 grit can sometimes be faintly visible if you look really close, depending on the lighting and color of the wood, so I try to use 40-50-60 grit or something like that. I dont see a reason to use anything finer than that. JMO.

Your question is really quite loaded as there are many other factors and applications.

[Robertfishes]

On one of my first builds, I used 36 grit spindle to grind a longbow riser to shape before glue up. The aggressive 36 grit was a little to rough and the glue line at riser and taper interface was not as pretty as when I used a 50 or 60 grit spindle sleeve. Lots of friends have seen this bow.. Nobody but me seems to notice this so it must not be to bad, we are our worst critics sometimes. it could have been due to a low quality sleeve, it left some deep trench's in the riser fades and back glue surfaces. I now have a Grizzly 6x80 sander, I just got it where i can use it. I used a 50 grit belt last night to grind fades on a maple riser, it went well but the riser is 1/2inch shorter now. I got a little aggressive getting one end paper thin, had to take a little off of the other side..

[LittleBen]

Manufacturer recommends 120 in the technical bulletin. I have used a variety between 120 and 36. I believe finer grit can produce cleaner glue lines. Especially when fading overlays and such.

[bamboo]

I've settled into grinding [final] the riser at 80g and final feathering the fade by hand with 100g[w/block]---lams and wedges at 80g--I can't remove enough material without burning---too course and the glue lines suffer too