Any idea what these are?

Probably a dumb question but I got these in a drawer of stuff on an auction a while back and I don’t really know what they are. They are varying sizes and diameters but they don’t seem to be exact measurements (ie, 2 in or 50mm). They don’t have markings and many have slightly rounded ends. Any ideas?

Looks like just dowel pins. Do any of them have threaded holes?

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As long as they’re hardened, that’s probably what they are.

Are they consistently 2-7 tenths under a common size? That would let you use an on size reamer and drop the dowel pin in the hole.

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Agree with Tim. They look like press fit, i.e.: interference fit pins. One grade below precision pins which are typically 0.XXXX" ± .0001" or .0002" Mic them, if they are all less than ± .0003" of a specific typical size, then they are most likely precision pins

The tapers are so they will guide into the hole without galling. These are often used in tooling as locators or for aligning two pieces together. The part with the pin will be a press fit, the other part will have a about .001" oversize hole so they will slide together and not wiggle. Often used on mechanical joints to to lock them in place for proper alignment while bolts are used to hold joint together - bolt holes having more “slop” or wiggle in them

I’d suggest wiping them down with something like 3-in-One il or put them in a pill bottle with some oil so they don’t rust. These are handy to have.


I few of the smaller ones do.

Those are used to extract the pins when they need to come out.

Our competitor uses tapered pins to hold alignment on their machines.