Hi,
I am working on flattening the top of a patternmaker’s bench my neighbor got on Craigslist. There are a number of divots, ranging from 1/4 inch drill bit sized up to 3-4 square inches that are filled with what appears to be Bondo. Am I correct that hitting a chunk of Bondo with a plane blade would be a Very Bad Thing?
I’m not sure how much time I want to devote to this bench, but if I wanted to get it really flat, would the best procedure be to remove the Bondo and glue in wooden patches that could be planed? What do you all usually do with a bench that has big divots? Assuming you don’t want to toss it and build another right now, that is.
Thanks,
Ted
Replies
Bondo is polyester resin mixed with talc. It sands easily, but would be difficult to plane, I should think. My guess is that the plane would react to your bondo plugs similarly to knots. Bondo won't break your plane blade, but it might dull it a little.
I find that when "green" bondo shaves off easily with a sharp chisel with blade oriented at an angle so that I am more "slicing" than "cutting", but once it gets hard, I have to work in successive passes no more than 1/4" wide.
If planing turns out to be a problem, you might simply dig out some of the bondo with a chisel or drill it out, then plane the table and re-fill the holes with bondo and sand flush with the table surface.
If a perfectly flat surface is not critical, you could belt sand the whole thing.
The Bondo may not be as tough as you think. I once tried to repair nicks in a tool rest for my lathe by filling the nicks with JB Weld, which is pretty similar to Bondo. The JB Weld filed down pretty quickly, and unfortunately for me, was soft enough that it didn't work out for filling out the nicks. I wound up buying a new tool rest.
I'd take an easy to sharpen blade, and just give it a try.
My experience with bondo is that it never gets absolutely rock hard - it stays just a tad pliable. I really don't think the amount you would take off with a sharp plane blade will ruin the blade - worst case it may dull a little sooner. But it doesn't sound like you will have all that much bondo on the top anyway.
Lee
Being a patternmakers bench it is very likely a product called Tufcarve or Tuffill. It is polyester resin with a filler, just like bondo, but the filler is wood flour rather than talc or fumed silica. It is much kinder to tools, especially if it's Tufcarve. If it is a nice even pine tan or mahagony brown it's likely one of the two. If it's the typical blue-green or reddish and inconsistant shades showing different bathces then it's probably bondo.
Rich
The Professional Termite
If it were my bench, I would remove all the bondo/filler, and put in a dutchman (wood patch) of similar material. Just my HO.
Jeff
My experience is similar to what Bruce described in that freshly cured bondo is relatively easy to shave, but fully sured, it's hard and brittle. Since Bondo is really made to be sanded when used as auto body filler, I'd be inclined to use belt sander (and a dust mask).
Wow, you guys rock, thanks for the quick responses. The stuff is much harder than the wood, so probably bondo. I tried a dutchman for one of the smaller spots and that worked well, but I'm starting to think it's not worth it to do that everywhere for the condition this bench is in. I'm seeing a lot of weird reversing grain, some splintery or peeling areas that are called 'loosened or shelled grain' in the Hoadley wood book, etc. I think I'll just get the worst of the high spots down and call it good. Nobody's going to do any precision work on it anyway. Sure is educational though!
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