Can you use painted wood in a planer without damaging the tool?

Question

I am about to inherit some all-wood bookcases that are about an inch and a half thick. They have at least one ugly coat of paint on them. Stripping it would not be worth the effort and I would think a planer could make easy work of them instead.

Is it possible that it might dull the knives more than just the wood alone? The potential of the knives chipping might be a important factor as well.

For arguments sake lets assume the paint is not lead based. I still plan on testing it but that is not the focus of the question.

Answer 1

Assuming that it isn't lead-based, I would probably tend to use an old set of blades if you have them. Some of that paint was incredible.

I would recommend running all of the boards through on an old set of blades at the smallest cut to take off the paint. If it isn't a latex based paint it will likely ruin a set of blades. Basically you just want to skim off as much paint and as little wood as you can get away with. (this will also save your good blades if there is any metal pieces hiding under the paint too) Then after they have all been run through put in new blades in and run them through to give them a nice clean cut.

I generally try other means myself but I have put some painted and stained boards through to save me some time and it will work, it helps if you have your planer hooked up to a good dust collection system, otherwise I would highly recommend using a high quality dust mask even if the paint isn't lead-based. And actually both safety measures would be a good idea.

Answer 2

I've found that pickling agents and scraper are a really ugly matter (and probably unhealthy even though nowadays it says "bio" on the label) and success is, well, mildly impressive. It's more impressive what drops of that nasty crap do to anything you don't want pickled (including tools and clothes).

The plane surely does the job (tried that once) but it's a bit like trimming your lawn with a flamethrower. Sure enough, it's a clean surface afterwards, but it's quite abrasive. If there is any kind of ornament (e.g. a bevelled or rounded edge) you will lose detail, and if there is a verneer over the edges (assuming it's not massive wood) you may damage that. Also, on any kind of plywood (wood core or otherwise) you can easily damage the surface beyond repair by cutting away the topmost layer of veneer.
Now to the actual question, is it safe for the plane? It will sure need some cleaning, but with most paints (especially old ones), I would seriously doubt that it will do any damage to the plane. There certainly exist paints which are about as hard as glass, but if you have one of these, you will know (you can tell immediately by looking at it). It's unlikely that you'll find one of the super-hard paints on some inherited bookcase.
Paint (old paint in particular) may of course contain metals (above all, lead), but hard wood is much harder than lead, so if that was a problem, you shouldn't plane any common hardwood like e.g. oak either.

On the other hand, I found that simply using 60-grain sandpaper (and later grinding "up" to 120 and 180) works wonders on old paint. Don't even need an electric tool, a plain old manual sanding block and going with the grain does it really, really good (and with a pleasing outcome).
Also, with sand paper you can go into the edges without taking the whole bookcase apart. It's a bit of fiddling, but you can do it. With a plane, you must take everything apart, there's no alternative.

Answer 3

I've sent painted wood through my surface planer and did not notice any particular dulling effect. This was typical interior latex paint; perhaps another type might behave differently. I suspect that the largest dulling effect would come from dirty painted wood rather than simply painted.

Answer 4

I only have one set of knives for my current planer and will soon be installing a helical head. I know a lot of people switch to an old set of knives to clean off paint, but I've also thought about dedicating a cheap, old lunchbox planer to paint and dirt removal. If you have a lot of reclaimed lumber to process, using an old set of knives or a dedicated planer will certainly get the job done quick.

Since I don't have a second set of knives, I've been using the process below on a piece of lumber before sending it through my planer to try to avoid dulling or gumming up the knives. Even though the helical head has carbide cutters that will stay sharp longer, I'll probably still follow this process since (a) I still want to prolong the life and avoid gumming up each cutter and (b) it would be a pain to rotate all the cutters to a dull side.

1. if it's painted, use a carbide paint scraper and/or an aggressive sander to remove any glue and most of the paint (not because I'm worried about the paint dulling the cutters, but because I don't want it gumming up anything in my planer)
2. brush it with a stiff-bristled wire brush to remove any embedded dirt and grit that could dull the knives (especially an issue with lumber that has been outside or that has been stored a long time)
3. visually check for any nails, staples, etc., that I didn't catch before scraping and brushing (if you have a metal detector wand, also use that)

Even if you're not concerned about gumming up the knives or cutters, I'd still scrape off any loose paint, hit each board with a wire brush, and do one last check for embedded metal before running it through your planer...unless you have a second set of knives or a second planer that's dedicated to the task of cleaning up reclaimed boards.

Answer 5

You're unlikely to notice any particular dulling effect from running painted surfaces through your planer. Some paints are made from harder pigments but they're not common in indoor paints these days.

There is another potential issue though, some paints get very 'gummy' when heated by friction and you could get some residue sticking to the blades or other parts of the interior. However this should easily clean up using acetone.

I would actually recommend you take one heavier pass rather than a number of very light passes. This way the blades contact the paint minimally.