Sanding Plywood Bullnose Edges

Advice on efficiently sanding the bullnosed edge of plywood panels before finishing. February 19, 2013

Question
We are applying a UV finish to a bullnosed plywood edge. We are having a hard time sanding the bullnosed profile smooth enough so that the final finish is smooth. We use two triangular sanding belts with profile sanding blocks. The first is 180 grit and the second is 220 grit. The 220 grit goes with the direction of the feed chain of the shape and sand machine. No matter what we do we don't seem to be able to make a consistent smooth finish so that we don't have to hand sand prior to sending the boards down the UV edge coater. We are running both the shape and sand and the edge coater full time each shift. Does anyone have any suggestions on how to get a smooth sanded edge on bullnosed plywood?

Forum Responses
(Finishing Forum)
From contributor Y:
Yes, add a 3/4" strip of hardwood to the edge. You can't sand plywood edges deadflat smooth because of the grain running two different directions between sheets of veneers.

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Question
I should point out that when we hand sand the plywood edge prior to sending down the UV edge coating line we receive a consistent and beautiful finish. However, this is time consuming and I would think there is a solution for achieving a better sanding job on the entire bull nosed edge when going down the shape and sand since that is what that machine is made for.

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From contributor F:
It’s hard to advise when we can't see firsthand. I'm wondering if your edges are still too course if you’re starting at 180 grit though? If you start at 180 you’re going to need a lot of sanding to get a smooth edge, versus starting at say 100 or 120 grit to smooth it out first then move higher to polish it up a bit. What grits are your guys using when they hand sand the panels?

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From contributor M:
You're going to have to try using a much finer belt and possibly giving it multiple passes if that's an option. Plywood edges in my experience can be sanded to a shockingly smooth texture and will even accept stain surprisingly nicely if you sand it with a random orbit sander with 220 or 320.

Since you are using a belt sander type, you may need to try 320 or even 400 since this is linear action and not orbital (self-canceling) action. Don't use anything that high of a grit on the face, but you don't need to worry about proper adhesion to the plywood edge when sanding super-smooth since it still tends to wick up the finish. I will note though that I have no experience with UV finishes. I suggest you do one with a high grit belt and test it afterward.