It’s pretty rare that I have to deal with rust on the table saw. In fact, there is only one time when it becomes a potential problem, I understand exactly how it happens, but it’s an uncommon occurrence, such that it happens maybe once or twice every couple of years. See, in my shop, I have ventilation fans in the roof that exhaust hot air. One of them is right over the tablesaw. When it rains, nothing gets through, except in rare circumstances when the wind is blowing hard and hits just the right angle to blow water through the fan. Then I might get a drop or two on the table saw, as happened in the last rain storm. Most of the time, I get out to wipe it off before anything bad happens. This time however, I didn’t and I ended up with a 3/4 inch spot of rust in the top corner of the iron top. So, as I do every now and then, I refinished the top, but this time I went completely crazy.
Table saws, and indeed any cast iron tabletop in the workshop, need occasional attention to make them function better. They get dirty through use, they get scratched, they get stained and, as I described above, they get rusty. Some shops where the ambient moisture content of the air is high, have terrible rust problems, you can have your tabletop go from clean to rusty literally overnight. Luckily, I don’t have to worry about that and if you are careful and protect your iron, it isn’t a big deal. Still, keeping it clean and smooth and slippery is an important consideration.
So the first thing I did was grab my cordless drill and slap a wire cup brush into it. I have numerous such brushes, including some that fit my angle grinder. The angle grinder moves much faster than the drill and can be much more aggressive, good for serious rust problems, but in this case it wasn’t necessary. I went through the table, section at a time, making sure I knocked off all of the high points, rust spots and anything that was stuck to the surface. When you run your fingers over it, it should be as smooth as you can get it.
Then I went back with my random orbit sander, starting at 120 grit and moving up to 220 grit, which is the highest I have for that particular sander. It gets smoother and smoother to the touch with each successive grit. Then I moved to my finish sander starting at 400 grit. Normally, that’s where I’d stop and I did the entire surface with that grit, but this time, I picked one cast iron wing and continued with 600 and 1000 grit, just to see what happened. It was noticeably smoother at the 1000 grit, exactly as if you were touching glass. Actually, forget that, it was smoother than glass. So I decided to try an experiment.
The last step in the process is to wax the table, you can use any non-silicon waxing agent but most people use Johnson’s Paste Wax, as shown in the picture above. You rub it on, let it dry and when it’s hazy, you buff it off. Here, I could have gone completely crazy, using my automotive finish buffer, but I didn’t, I just rubbed it off with a paper towel. I did this on the one wing finished to 400 grit and the one finished to 1000 grit. Both were extremely slippery. To test how slippery though, I got a block of wood and pushed it across the tabletop with equal force on both wings. It went noticeably farther on the wing sanded to 1000 grit. I performed the test several times to make sure I wasn’t providing more force on one side than the other and it was consistently better on the 1000 grit wing. Now I’m going to go back and re-sand the rest of the top to 1000 grit and re-wax everything.
There is a point of diminishing returns, of course. I could continue sanding to 1200 or 1500 grit but there comes a time when the extra effort won’t give you significant returns. The amount of material that you’re taking off at those higher grits is really minuscule, I probably could have stopped at 600 or 800 grit and gotten nearly the same results. But I’m crazy, what can I say?
For most people, refinishing the top of their table saw should be done once or twice a year, more for areas with high humidity. The top ought to be waxed every couple of months to keep it from rusting at all. There are several professional lubricants like Boeshield T-9 that I’ve used in the past, in fact I have a gallon jug of T-9 sitting around somewhere that I use to waterproof all kinds of things but I haven’t noticed it working better on a tabletop than just plain paste wax, which is why I don’t use it there.
Well, back to the grind… I mean the sanding. After I do my table saw, I’ll move on to other tools with cast iron tables, I know that my scroll saw is looking pretty ratty and deserves the same treatment. Let’s see just how slippery and smooth I can make that one!