Erector set screw size

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 to replace damaged or missing originals, or just find them easier to work with.

Erector set screw sizes

Erector set screw size
Erector set screws were standard 8-32 and 6-32 machine screws of various lengths.

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.

Gilbert part# Type
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.

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 it together. 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.

One thought on “Erector set screw size

  • February 15, 2020 at 10:15 pm

    I remembered the Erector Set I had as a kid and as I was going to visit ACE for some nuts and bolts for a radio (Older Japanese, metric of course) this question occurred to me. For who knows why.
    I also remember the square nuts for the (Erector Set) included hardware. Which now seem rather peculiar.
    p.s. ACE had the 2.5mm machine screws for my old transistor radio and it’s doing fine.


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