Replies

1. 
   cadiddlehopper | Sep 12, 2006 03:55am | #1

   Polyurethane might gum up your knives if not dull them quickly. The same is true of glue. Some plastic resins can melt due to friction, others are extremely abrasive such as glue in plywood. Don't try power sanding either. A belt will fill in a flash. Of course, if you can sharpen your knives & don't mind the wear on them, you just might be able to plane off a few boards. I wouldn't.

   Cadiddlehopper

1. 
   SteveSchoene | Sep 12, 2006 06:48am | #3

   Polyurethane isn't going to have a big negative effect on the planer knives.  It's a lot softer than most woods, and softer than most other varnishes.   Ordinary dirt is a bigger problem.  As long as the poly has a few days o cure you will be just fine running it through a planer. 

1. 
   cadiddlehopper | Sep 12, 2006 05:56pm | #4

   Have you run stained & polyurethane coated boards thru your planer? Did you examine the cutter afterwards? It is my policy to treat keen edges with more respect than that, but if you have had the experience, I will defer to your expertise.Cadiddlehopper

1. 
   SteveSchoene | Sep 13, 2006 12:50am | #8

   There would be more likelihood of damage with paint--due to abrasive properties of some pigments, but polyurethane, with no pigment, isn't going to have much in the way of abrasiveness.  Consumer poly is pretty soft stuff.

   And, yes I have run varnished boards through a planer--typically when I have been testing finishes and want to reuse a scrap board.  I observed no ill effects.  Subsequent bare boards were just as smoothly planed as before.  Might be a different story with 1000 bdft of old painted boards, but if that's the project new planer blades would be cheap compared to the alternatives. 

1. 
   cadiddlehopper | Sep 13, 2006 03:49am | #9

   Thanxx!! for the reply. Please let me know when you have planed off polyurethane. It is a resin for which I have great respect. Come to think of it, my planer blades need to be serviced. I may try it myself if I can bring myself to do it. I also have some small panels veneered with yellow glue that I could try. I anticipate some kind of damage.Cadiddlehopper

2. 
   SteveSchoene | Sep 13, 2006 12:34pm | #10

   I have planed off polyurethane--though only a few times since I hardly ever use poly since I don't do much floor finishing, the only place where it's really useful.  Single part poly is just one kind of varnish, softer than the traditional resin varnishes, and much softer than hard finishes such as shellac or lacquer.  The abrasion resistance of poly doesn't come from being harder, but from being more elastic. 

   And, in any event, the hardness of the various plastic resins is so much less than the plane blades that it's not going to be a major source of wear.  Pigment on the other hand often consists of particles of metallic oxides which may be quite a bit harder than the resins in the binders.   

3. 
   cadiddlehopper | Sep 13, 2006 08:51pm | #11

   Don't forget heat. Sanding or planing will heat the stuff. It could become a gummy mass. I'll post the results if I try it.Cadid

4. 
   bd | Sep 17, 2006 12:27am | #12

   I've run hundreds of feet of polyurethaned red oak boards thru my planer. We tore up about 1000 sq ft of red oak flooring. I'm cheap. Wasn't about to throw that stuff out. So far I've run about 1/2 of that thru by 12" portable planer with no problems.

5. 
   cadiddlehopper | Sep 17, 2006 02:59am | #13

   Thanxx!! for the input. That makes me fear the results of my own experiment a lot less.Cadid

6. 
   PADDYDAHAT | Sep 17, 2006 07:28am | #14

   bd, nice to know, thanks, I just had 600 sq.ft. of prefinished oak laid in my TN. digs and I had lasered the space for 550. The mechanic bought a skid of 600 so I won the two extra boxes of flooring. Hey I paid for it ! It's good to know that I can run it through my planner if I need to remove the finish or to flatten the back on the joiner. I have used it in the past to plank out a platform for a bay window rather than use the standard ply deck and an edge cap, it really looks sharp. Thanks again. Pat

2. 
   DCarr10760 | Sep 12, 2006 04:15am | #2

   I've got a cheap lunchbox planer that I used regularly to knock off old paint and finishes so I can re-use the lumber.  Its blades are nicked and dull and it leaves an awful finish, but I follow it with a handplane anyway.  So I consider it a rotary scrub plane.

   Voluntary Disclaimers:

   Dust collection is obviously a must when doing this and I certainly wouldn't do it with a planer that you intend to immediately afterwards run fine hardwoods through.   Be sure to read and thoroughly understand your instruction manuals before operating the equipment.  Use eye protection and hearing protection and a respirator and a flack jacket, wear a pith helmet and use SPF 50 or greater sunblock if you are working outside.  Wood and finish particles in the air as small as .5 microns are discharged during this and like processes, common dust collection systems cannot filter 100% of pathogenic materials from the air so use this and all similar techniques at your own risk.

   But have fun!

   David C.

3. 
   forestgirl | Sep 12, 2006 06:45pm | #5

   When I first got my planer, I asked the same question about some painted oak boards.  What convinced me it was a bad idea was the mention that the planer heats up with use, which can soften the paint and gum up the rollers.  This topic comes up a few times annually, and much is discussed about knives.  Overlooking the rollers and the cutterhead.  These would not be parts fun to clean softened, gummy finish off of.

    

   forestgirl -- you can take the girl out of the forest, but you can't take the forest out of the girl ;-) 
   

1. 
   DCarr10760 | Sep 12, 2006 09:59pm | #6

   Forestgirl,

   After running bunches of painted boards through a cheap 12-inch planer, I haven't experienced heat softened paint transferring to the rollers.  Chips do get pressed on, but are easily wiped off with a stiff brush when everything's still.

   I suppose it's possible theoretically, but you must have to do more than I've done (hundreds of feet, not thousands).

   Best Regards,

   David C.

1. 
   Lataxe | Sep 12, 2006 10:44pm | #7

   I too have planed varnished and glued-up boards through a planer-thicknesser (with HSS knives).  The only glue that seems to damage knives is cascamite or resin - glues that dry hard and brittle.  The glue line can put nicks in the knives.  Other glues have no effect on the knives.

   The other danger with painted or varnished timber is hidden nail heads, embedded bits of stone and similar hard stuff lurking under the paint or varnish.  If I suspect that such stuff lurks, I plane off the timber with a handheld electric planer using TCT knives.  They often plane off soft metal nail heads and seem to deal with the hard glues OK. 

   Even if you do nick them, they are a lot cheaper (and easier) to replace than HSS knives in a jointer or planer/thicknesser.  I put up with any nicks in the hand-held planer blades as long as the plane still takes off most of the grurk.

   Lataxe