The working diameter dictates the pin size in a "standard" off-the-shelf spanner wrench. Go look at McMaster Carr or some other supplier, they have dimensions for spanners ranging from an inch to 6 inch working diameter.
So, if the "working diameter" is say 11/32" then that should be the hole size that fits the spanner wrench pin which is manufactured slightly smaller to fit the hole?
Working diameter is meant to be the size of the circular nut or object being turned by the wrench, as opposed to "pin" diameter. If you're speaking of clearance or tolerance between the pin of the wrench and the pinhole in the nut, you could use 1/64" clearance for pin sizes under 1/2 inch, 1/32 for 1/2 to 1 inch, and 1/16 for 1 inch and over. This does not come from a published standard, but rather my own (many years of) shop experience. Good luck.
I looked at McMaster Carr and wanted to get a 3-1/2" pin style wrench
5475A22
Fixed Pin Spanner Wrenches for Holes for 3-1/2" Circle Dia, 11/32" Pin Dia, 5/16" Pin Length
Should I make the mating part hole 11/32" or 1/64 larger for clearance? I was thinking that since they said 11/32 pin that they meant that it would fit a 11/32 hole.
1) Buy a couple of the wrenches from the catalog. (Enco will be less expensive than most others. Sears also has spanners.) Measure them. Use that measurement.
2) Specify BOTH the hole size (minimize the gap since that allows a "twist" that tears out the metal and strips the device you're trying to turn!!!) and the distance between holes. I recommend a +0.000 -0.xxx specification on hole size so you don't go oversize.
Fromthe two or three wrenches available, choose the largest that will match your device. In other words, find a common wrench that will fit, then define your holes so a "common mechanic" can get wrenches that will turn it.
