Eliminating Cross Grain Scratches
Tips on detecting and preventing cross-grain scratches created during sanding. October 25, 2006
Question
One of our biggest problems when finishing a cabinet is removing cross grain scratches. The guys in our shop say they have a hard time seeing some of the finer scratches and swirl marks so they aren't able to sand them out. Occasionally I can't see some of them myself, especially if we are using maple. My question is, does anyone know of a good way to catch these scratches? I seem to remember reading about using UV lamps to look over the cabinet boxes to check for scratches. I'm willing to try anything.
Forum Responses
(Cabinetmaking Forum)
From contributor J:
Paint thinner or mineral spirits will allow the scratches to show as the stain does without raising the grain. I always drop below my last grit on the widebelt when changing to orbital sanders. If I sand to 180 on the widebelt, I'll drop to 150 or 120 when beginning with an orbital. Make sure you go at least to 180 with an orbital and don't skip grits. I would also advise not going below 100g when leveling everything with the widebelt. Those 80g scratches are very hard to get out.
From contributor F:
Besides mineral spirits, viewing the sanded wood parallel to the light source shows the defects better than a light that shines directly on the surface. In other words, sideways or "raking" light shows the imperfections better.
From contributor E:
I keep bumping into this problem, and I always know what the solution is - light! I have basic 8 foot T12 shop lights in the area where sanding happens. After changing the spray booth over to 6500k T8s (and a bunch of them) I now realize I've been working in a pink fuzz for years. I can see, but I really can't see.
At one point, I'd hold a surface so I could get a view from the bay door and outside light running across the panel or edge, but low light fixtures would really help, and be darn sure they're daylight type light. I'd say light up the sanding table with low height lights, so you can see across the grain. Sounds like a lot of trouble.
From contributor D:
The other guys are telling you some very good advice for your cross-grain problem in terms of the light needing to be closer to the material and raked rather than high above. But one thing I would add, is that in conjunction with the raked light, make sure the lights above your operator are at a proper angle to allow for a certain amount of shadow. If the overhead lighting is approximately 45 degrees behind your off bearer, and the raked lighting is at approximately 45 degrees to the top of the material coming out, it should show every defect in the sanding and the material. Hope this helps.
From contributor M:
You don't need UV light. As these guys have said, it is the angle of the light. My guys use the halogen construction lights, the ones on an adjustable stand. You might want to do a search for 'inspection' lights. There are some that you can buy and put at the end of the widebelt. They look like a row (maybe 4 or so) put on a tripod or stand. Also - the halogen lights work great in the winter because they develop a good deal of heat.
