Tool Maintenance – Protecting A Cast Iron Tabletop
- Grey Scotch-Brite Pads (7448)
- Some sort of treatment such as…
- 0000 Steel Wool (instead of the Scotch-Brite pads)
- Denatured Alcohol
- Bag Of Rags
- Blue Painters Tape
- Blue Shop Towels
- Hand Pad Holder or Sanding Block
Cast iron gets rusty. Period. You can take steps to help prevent it but you’ll still have to deal with it eventually.
In my case, I have a SawStop Industrial Cabinet Saw with an additional 10″ cast iron wing that has some rust forming on it. It’s not too bad but I should definitely do something about it. You can see a big greasy hand print right on my right miter slot. (How that happened is a long story but rest assured, our lights work now.)
A close-up of the hand print shows that it isn’t pitting yet so it should mostly come off.
The paw prints are a bit more severe. I don’t see any pitting but I won’t know for sure until I scrub it away.
Here are a few more paw prints.
I don’t know exactly what caused these rust bands but I am assuming that this is from moisture being locked under boards that sat on the table top for a day or two. This is why you shouldn’t leave wood sitting on cast iron overnight, especially during the summer.
Another mysterious rust spot. It isn’t too bad so it should mostly come off.
Removing The Rust
Some people prefer to use 0000 steel wool to remove rust, and it will do a pretty good job. Personally, I prefer to use Scotch-Brite 7448 pads. These are the grey pads, not the green ones you use in your kitchen. They are the same grit as 0000 Steel Wool but you can use a sanding block to apply even pressure over the entire pad. This is a lot harder to do with steel wool.
Next, I apply a generous coating of WD-40 to the entire table top. You want to let it sit for a while so it can penetrate the iron and start to break apart the rust and even some of the slight discoloration that cast iron can sometimes get. I will typically let it sit for at least 15 minutes but in this case I let it sit for about an hour and a half.
You should scrub in a front-to-back-to-front motion. Try not to focus on one little spot since that will lead to an inconsistent shiny spot. Instead, use some elbow grease and cover the entire depth of the cast iron.
I like to scrub until I at least get a dark slurry started. It will typically require more scrubbing if your table top is as rusty as mine was.
After tackling the entire table top, I do the bulk of the clean-up with blue shop towels. The table top should look a lot better at this point.
If rust sits for a while it can permanently discolor the cast iron. You can see this below. The rust is gone but the iron is stained. Personally, I’m cool with this. It doesn’t affect the usability of the saw.
The hand print is mostly gone. I can still see a slight shadow but you have to know it’s there in order to see it.
Surprisingly, the paw prints are completely gone. I thought these were going to be there forever.
Technically, you can stop here. I find that no matter how much I scrub with shop towels I can never quite get all the WD-40 up. This leaves a slightly greasy feeling to the table top which can transfer to the material you are cutting. I find that the best way to clean this up is with denatured alcohol.
The cast iron is now completely exposed and needs to be protected.
Protecting The Surface
There are many ways to protect the surface of cast iron tools. I’ve had good experiences with T-9 BoeShield or GlideCote, but I personally prefer using a furniture wax like Johnson Paste Wax, although MinWax and Renaissance Wax will work as well. I like Johnson Paste Wax since it is softer, which means it applies easier and also buffs out a LOT easier than either MinWax or Renaissance.
Apply the paste wax to the cast iron. You don’t need to apply it in any particular fashion, just be sure to get it all over.
After you have the table top coated, let it sit for a while. I usually let it sit for about 15 minutes.
Use a fresh rag to wipe the wax off and buff it out. This can take some experimentation but the way I handle it is to use one rag to wipe the bulk of the wax off but I don’t worry about it looking good yet. You’ll still have some streaks and maybe a few missed blobs of wax. After that, I take another fresh rag and wipe it down to buff it out. You’ll notice that when you first start buffing it, the table will be slightly “grabby” with the rag. Just keep buffing. You don’t really need to apply much pressure or buff in any particular direction, just go back-and-forth for a while to build up some friction. You’ll find that eventually the table will get very slippery. That means you’re done and ready to move on to the next section.
After you finish, I recommend that you apply at least two more coats of wax.
That’s it. You’re done. You now have a nice slippery cast iron table top that won’t rust up as quickly (if at all). I like to repeat this process as needed, which may be every six months or every six years. It all depends on how you use your saw.
Also, it is a good idea to apply some paste wax to the exposed metal on the front tube where the fence rides back and forth.