I've got a double Nervar cottered (3-arm) crank that I am thinking of running it as a 1x if I can source shorter chainring bolts. Are these a standard thread and pitch?

Thanks for the help!

Take the cranks to a local hardware store with a large by the piece inventory of nuts and bolts and experiment to find out.

I don't know but they are probably a standard metric thread. Get or borrow a thread gauge and caliper. Measure them.

The crank appears to take a standard M7 bolt, which I scooped up from the neighborhood hardware store. They did not have anything shorter than 10mm in length, so I will have to cut about half the threads off.

I will post a photo of the results later.

FWIW those bolts are a sort of standard that was used on older cottered cranks with removable chainrings.

As a result, they are easy to find at a coop bike shop, in the bin marked 'cottered cranks'. The Brits may have had their own thread pitch...

Crank with standard M7 bolts and washers installed. The 10mm length only pokes through a little on the other side.

Well done!

They aren't as "low profile" as the old bolts, but they are only noticeable from the nondrive side and will likely not cause any interference with the frame.