Erector sets frequently are missing screws, or they have screws but they’ve suffered the ravages of time. Fortunately the Erector set screw size was a standard 8-32, so you can substitute modern screws and/or nuts to replace damaged or missing originals, or if you just find them easier to work with.
Erector set screw sizes
Depending on the set, Erector sets came with standard 8-32 thread screws of 1/4 inch, 1/2 inch, 7/8 inch, 1 3/8 inch, and 1 3/4 inch. Not every set necessarily came with every length.
Some Erector sets also came with 3/16-inch 6-32 screws to use as set screws for holding pulleys to motor shafts.
|S51||8-32 ¼ inch|
|S52||8-32 ½ inch|
|S57||8-32 7/8 inch|
|S62||8-32 1 3/8 inch|
|FA||8-32 1 ¾ inch|
|S11||6-32 3/16 inch|
Most sets came with square nuts to go with the screws, though in 1947-48, sets came with hex nuts. If you find the old screws hard to work with and want a modern screw head to use, or just like working with clean parts, hardware store 8-32s work fine. If you want authenticity, a slotted screw head was what vintage sets used. But if you want to spend less time fiddling around, a Phillips or Torx head certainly can be nice. If you want both authenticity and convenience, put a little bit of Tacky Wax on the head of the screw. It will make it stay on the driver more readily.
6-32 and 8-32 are two very commonly used screw sizes.
Restoring Erector sets screws and nuts
If your Erector set’s screws and nuts are rusty and dirty, you can fix them rather than replacing them. I’ve had some success restoring old nuts and bolts by tumbling them in a children’s rock tumbler along with bits of aluminum. I’m talking tabs off soda cans, scraps of aluminum foil, stuff like that. Aluminum oxidizes more readily than iron, so it’s happy to steal the oxidation from the iron just by rubbing up against it. So throw some rusty nuts and bolts in a rock tumbler along with a larger amount of aluminum junk and let it tumble for at least 30 minutes.
If aluminum junk doesn’t quite cut it for you, you can use specialty rust-cutting resin tumbler media.
Another trick is soaking them in a weak acid. Vinegar readily eats rust, but I find if I don’t rinse it thoroughly and dry them super fast, the parts flash rust on me. I’ve had more success removing rust with lemon juice, even though it works more slowly. Mix 1 part lemon juice to 4-6 parts water and let the parts soak overnight.