The International Space Station (ISS) is a joint construction of many countries around the world. Most of whom use the metric system for measuring including sizing of bolts, nuts and fasteners.

The US seems to be stuck on imperial units, while the rest of the world has moved to Metric and anyone who has worked on both an American automobile and one from just about any other place in the world, has found out the nuts and bolts are different. In fact you need to have two sets of tools, one SAE (American) tool set and one Metric tool set.

Are nuts and bolts on the ISS, metric, SAE, or both?

  • 7
    $\begingroup$ It's worth noting that NASA has stated they will only accept metric nuts and bolts on the Moon, although it seems the ISS still uses both. $\endgroup$
    – PearsonArtPhoto
    Oct 21, 2015 at 13:10
  • $\begingroup$ @PearsonArtPhoto if that is the case, I am assuming that applies to new stuff as I suspect all the Apollo stuff is SAE, which means you might need to update your answer here if you don't have SAE tools, everything there now is just going to be scrap. $\endgroup$ Oct 21, 2015 at 13:19
  • $\begingroup$ Yes, that only applies to future missions, I think the decision was made in 2004 or so. I'm sure they'd bring tools if they were going to work with Apollo hardware. $\endgroup$
    – PearsonArtPhoto
    Oct 21, 2015 at 13:30
  • 3
    $\begingroup$ The US doesn't use the Imperial system of units and never has; it uses the US system. The Imperial system was created after American independence, and for understandable reasons wasn't adopted in the US. But both systems use the international foot and inch, so as far as nuts and bolts it doesn't matter. $\endgroup$
    – hobbs
    Oct 21, 2015 at 18:59
  • 2
    $\begingroup$ @called2voyage: I wonder how durable the 3D printed items are. Normally tools need to withstand quite a torque, especially if you tighten a bolt on an airtight, pressurized seal. $\endgroup$
    – SF.
    Oct 23, 2015 at 16:02

1 Answer 1


Both, apparently, at least the ones the crew can access. Their toolbox features both systems.

enter image description here

  • 4
    $\begingroup$ Is that a sonic screwdriver in the lower right of the tools? ;) $\endgroup$ Oct 21, 2015 at 13:01
  • 1
    $\begingroup$ A closer look at the image here makes it appear that darker blue is Metric and the Lighter Blue is SAE. It is pretty easy to read some of the fractional socket sizes, the #mm are a bit harder to read in the photo $\endgroup$ Oct 21, 2015 at 13:09
  • 3
    $\begingroup$ In most of the parts drawings I've worked with (granted they're for US-built components), all of the fasteners were NAS (National Aerospace Standard) parts, which generally follow SAE fastener sizes. $\endgroup$
    – Tristan
    Oct 21, 2015 at 15:37
  • 3
    $\begingroup$ Note that they can also 3D print tools on the station now. So if you need some non-standard tool for the job, they'll just beam it up... :D $\endgroup$
    – TildalWave
    Oct 21, 2015 at 16:37
  • 4
    $\begingroup$ That 3d printer only makes plastic tools. OK for low-torque applications, I suppose. $\endgroup$ Oct 21, 2015 at 21:01

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.