I recently inherited an old Delta table saw from my Grandfather, but had no good place to put it other than in a ruddy old shed. In a short time, the cast iron top of the saw started rusting. I had tried the quick rust fixes... vinegar... using a tarp to protect the table... but the rust came back.
Rust is cancer! It spreads, and to stop it you must kill all of it! Rust killed my first car and my parent's above ground pool. I wasn't going to let it take my grandpa's saw too!
This requires no special tools, and can be done rather quickly, and was much easier than I had thought!
Step 1: Manual Removal
Access the amount of rust you actually have. If there is only surface rust with some minor pitting (When the rust has eaten into the table top) then clean up won't be so bad. The best thing you can do is catch it early!
If your metal object has been sitting out for years and has major rust damage, it may not be worth anything when you get the rust off... :-(
For a table saw to be effective, the table needs to be flat. In my case, My saw was covered in rust, but only had minor pitting.
Begin working with a stiff metal bristle brush. (like these from Harbor Freight: http://www.harborfreight.com/3-piece-heavy-duty-w...)
Take your time knocking off the larger chunks of rust and scour the whole surface. Be wary of how much rust dust you're kicking up in the air, it might be a good idea to wear a mask and eye protection!
Finally wipe the surface clean with some paper towel. If you do a good job here, the following steps will be easier.
Step 2: Chemical Removal
Skip the Vinegar and go for some good old-fashioned Naval Jelly (6 to 8 Bucks at your local Hardware store)
This stuff works quickly and does a great job. It's a thick, gloopy jelly made of mostly Phosphoric Acid. WEAR GLOVES when handling this stuff.
Brush, or glob on to your rusty surface and spread it around. Allow a thick layer to sit and work for 5 to 10 minutes, then wipe it up along with the rust. It can be thinned and sprayed with a paint sprayer if you have a large area to cover.
After removing the surface rust, apply more jelly to the pitted areas and use some elbow grease and a rag to work it into the rust. Use a clean metal brush if you need to. The rust comes up in no time!
Step 3: The Details
In the first image you can really see the difference that jelly makes!
To get the last bits of rust off the table, and from within the miter slots, a little hand sanding will be needed.
I take some 400 grit wet/dry sandpaper and use the Naval Jelly as a lubricant for some set sanding. Here, a little goes a long way.
For big flat areas on the table top, I attached some of the sandpaper to a flat board with some spray adhesive. This makeshift sanding block covers a lot of ground quickly.
I used a dab of jelly and a small scrap of sandpaper for the finer details and hard to reach areas like the miter slots, and the walls of the "throat" where the throat plate and blade reside.
When finished, you need to rinse the surface with water to remove any residual acid. Rinse with a water soaked rag and dry thoroughly.
Step 4: Protect It!
After all the Cancer is removed, protect your metal to prevent it's return.
Once the surface is dry I covered the surface with WD-40, and spread it thin with a rag. Then, I used some more! Protecting your metal tools with WD-40 is a great thing to do if you store them for a cold winter like I do. (For those of you who don't know, the WD in WD-40 stands for Water Displacement. Rust prevention and removing water from mechanical systems was the original designed purpose of this product, but now it has hundreds of uses)
Alternatively, you can protect the surface of the table with a coat of paste wax or paraffin wax. These waxes also smooth the surface of the table saw so wood can more easily glide across it. There are also specialized products like Bostik Top-Cote (https://www.amazon.com/Bostik-10220-Aerosol-Top-Co...) that are meant for this purpose.
DISCLAIMER! Only use WD-40 if you aren't planning to use the saw for a while. If you use the saw after it has been freshly lubricated, WD-40 can be picked up by the wood you are using and cause major issues when you are trying to apply a finish to the wood.
I hope that this instructable helps you out. Now get to work with that saw!