Chris Schwarz's Blog

Scrape Your Saw Clean

I have always been fastidious about keeping rust off my tools. I have to be. My shop is partially underground and we live in a humid river city. Blink, and your tools will turn to iron oxide.

The most difficult tools to keep rust-free are the machines, especially my Unisaw for some reason. The cast iron in my old Powermatic jointer is almost impervious to rust, and I don’t have a good explanation. The iron appears very finely grained, or at least is finished to look that way.

Anyway, a couple months ago we had a party at our house, and a lot of non-woodworkers ended up in my shop, drinking beer and hanging out.

The next morning I cleaned up the house and found several beer bottles sitting on my Unisaw. And each had deposited a nice rusty, crusty bloom on the iron top.

Grumble.

I took some steel wool to the rust. No luck. Then I tried a variety of other chemical and abrasive treatments that had worked before. The iron was still stained and coated with some nasty, nasty rust.

I looked around and wondered what to do. My eyes alighted on my Benchcrafted carbide Skraper. I use this tool all the time to scrape dried glue off panels (when I leave glue behind). It is an awesome piece of equipment.

I thought: Carbide is way, way harder than iron.

So I gingerly stroked the Skraper across the iron top, and a layer of rust came off. I used a little more pressure and the top was clean, as in “new” clean — and the milling marks from the Blanchard grinding faded a bit.

Now, I don’t want to upset the machinists here. I know that scraping an iron top by hand will take it out of flat. But I contend that your table saw top’s flatness does not have to be like a machinist’s granite plate for your saw to work really well.

Once I scraped the top, I looked at it with a straightedge and feeler gauges. It was still really darn flat. The rust is gone, and the saw works fine.

I’d do it again. But then, I’m not a machinist.

— Christopher Schwarz

Yup, I Have Power Tools
“Don’t believe everything you read on the Internet.” I believe Socrates first said that. I do have power tools, but they are few and they are in subservience to the hand tools. But if I did want to abandon all my power equipment, I’d read Jim Tolpin’s “The New Traditional Woodworker,” which is a book about one man saving his soul through hand tools. It’s a great book.

31 thoughts on “Scrape Your Saw Clean

  1. JWatriss

    I second (third? fourth?) the paste wax idea. We used Butcher’s at NBSS, I use something else in my shop. The important part is that it’s a beeswax/ carnauba mix. The beeswax wears off pretty quickly, but the carnauba builds up over time, and is much harder.

    And if I have folks over to the shop, they’re made to understand not to put beer down on the cast iron. Good fences and all that. Or, you could make a masonite cover. Double-duty, makes for a decent glue-table.

  2. richardrank4

    I found tht beeer cans aren’t the only problem creating rust. One night I left a freshly cut piece of cedar on my new band saw table. I removed the rust, but a cedar stain remains. Dick

  3. Mike M

    Machinists use carbide scrapers to flatten and rework small or hard-to-access areas. Machine tool ways (the bearing surfaces for the tool rest on an engine lathe, the work table on a milling machine, etc)are flattened with such a scraper. This makes ‘way oil’ stay on these surfaces. A sort of cross-hatch pattern is used; it’s called frosting, and resembles a lightly ice-frosted glass. It has to be hand finished. The shop I apprenticed in used a 2″x 1/8″ piece of carbide silver soldered to some 2″ cold rolled steel.
    Your actions are machinist-approved.

  4. BillT

    I also made a cover of thin plywood with a little lip around it to flop on the saw. It gives me another surface to use when I don’t need the saw. I use it as an painting/varnishing/glueup/assembly table. The surface covers not only the table, but also the fence rails, so nothing gets dripped on.

  5. BillT

    I live in a relatively humid climate (central Virginia). I always keep a good coating of paste wax on all my cast iron machine tables (Unisaw, bandsaw, etc.). Butcher’s Wax or Johnson’s Paste Wax works fine. It not only prevents rust, it also helps the keep the surface nice and slippery to make it much easier to slide the work over the table, so you can focus on controlling the cut, rather than on pushing the piece over a sticky, frictiony (if I can make up that word) table.

  6. Bill

    Chris,

    I got tired of constantly cleaning my saw table because my shop cat likes laying on it in warm weather. I finally found one of those large magnet saw covers; its like a Huge refridgerator magnet and it works terriffic.

    You do need to ensure ALL moisture is removed prior to laying it on the saw. Otherwise you are in for a real suprise next time you remove the cover. The magnet will keep the moisture from evaporating and seal it on to your table causing REAL rust problems.

    However, I still think its the best solution with just a bit of wiping prior to laying the cover down at the end of the day.

  7. John Cashman

    You need more friends, and more beer. Be more careful about how you space the sweaty cans on the cast iron top. Remove only the loosest part of the rust, and then tell everyone you have an engine turned top.

  8. robert

    A friend of mine works in a professional cabinet shop and at his shop they use a non-silicone paste wax made for furniture. Put it on, buff it off. Slick and shiny. Also, a cover for the saw is a good way to prevent inadvertent placement of sweaty objects onto a saw’s surface.

  9. BLZeebub

    That’s why I COVER my machine tops whenever “the crew” shows up for libations. I live in near 100% humidity here in central FL so it’s always a thing to consider. I’ve learned to simplify my top treatment by rubbing it down occasionally with a piece of wax paper. Yepper, no fancy schmancy lubes or supermarific spooge just a plain old hunk of cheap wax paper. NO PROBLEMO. My biggest gripe with my old Powermatic is having to degrunge the worm gears.

  10. Roseville Rob

    Here in the Central Valley of California, my biggest problem is when I sweat on my table saw table even with a sweat band. I am working at the table saw in a garage with a west exposure and I perspire allot. If sweat drops onto my saw and I don’t wipe it off before it dries, the next morning I have little rusty splatter marks. I use the grey (finer than the green) synthetic pads by hand. These pads are designed for metal polishing, not the green scrubbing pads for dishes. The ROS is a GREAT idea. Boeshield helps, wax helps, but I still get little splatters.

  11. Bob Miller

    I have had really good luck doing something similar with a utility razor blade used like a cabinet scraper. It has the advantage of being somewhat softer than the cast iron but harder than the rust so it tends to just take off the rust and leaves a protective patina (also nice looking on old machines IMHO). I have cleaned a whole table saw table, a jointer and a planer this way. I used WD-40 as a working fluid and it goes pretty fast and leaves a nice smooth surface.

    Scraping can actually be used to bring a table back into flat (according to an owwm article http://wiki.owwm.com/Flattening%20Cast%20Iron%20Surfaces.ashx#Scraping_5) and is/was actually used by machinists to create ultra flat surfaces.

      1. LanceG

        Hey, now, traditional german brews were usually served room temp, back in the day. Well, cellar temp actually. It’s just the mass-produced, rice-based macro-beers that REQUIRE refrigeration to be drinkable!

        Not that I have anything against an ice-cold triple hop ale on a summer afternoon. Mmmmm. Hey, is it quittin’ time yet??

  12. Nick

    Were you dragging it across the table (think card scraper) or were you pushing (think paring chisel)? Also, were you pulling up iron chips while doing this or just dust? Scraping can be the best way to bring a metal surface to ultimate flatness; high end machine tools have always had their critical mating surfaces hand scraped. The Home Shop Machinist magazine’s latest two issues have great articles about scraping (not to mention alot of other great stuff) and there are some serious implications for a ridiculously flat smoothing plane sole. I wouldn’t hesitate to knock down some high spots on an out of flat machine surface even if they weren’t rusty.

    1. Christopher SchwarzChristopher Schwarz Post author

      Nick,

      Pushing and pulling. I was pulling up corrosion for the most part. But I’m sure there was some regular iron in there.

      I’m aware of scraping plane soles and have tried it. But the scrapers needed a lot of sharpening…. This process didn’t even harm the carbide tip. The Skraper still cuts like butter.

  13. Al Navas

    Good for you, Chris!

    About two years ago we hosted a local Woodworkers Guild meeting in our shop. Six cold cans placed on the Unisaw top created similar nasty corrosion rings. I put a green synthetic pad under my ROS and went to work on the cast iron. Nice results, with all evidence gone in a matter of minutes.

    A little Boeshield T-9 followed by Renaissance wax, and I was back in business, but still upset that friends had been so careless.

    Al

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