AN3 hardware bolt head identification

[dbaflyer]

I pulled some bolts out of inventory for the aileron bell crank assembly. AN3-10A. They would not fit through the 3/16 inch holes reamed in the top and bottom assemblies. I tried another AN3 bolt and it fit just fine. The two bolts have different markings on the top. The bolts that fit have "A F C" and an "X" on them. The ones that don't fit have "OIDO" and an "X". Is there a difference in this hardware?

[Bob Kuykendall]

Note that standard AN hardware is not particularly precise. I think that the specified range for AN3 is 0.186" to 0.189". So if you've precisely reamed a hole to 0.18750", you will find a certain number of AN3 bolts that are within spec but won't fit.

That's why I usually drill AN3 bolt holes #12 or #11 depending on material and application.

Thanks, Bob K.

[az_gila]

Originally Posted by Bob Kuykendall

Note that standard AN hardware is not particularly precise. I think that the specified range for AN3 is 0.186" to 0.189". So if you've precisely reamed a hole to 0.18750", you will find a certain number of AN3 bolts that are within spec but won't fit.

That's why I usually drill AN3 bolt holes #12 or #11 depending on material and application.

Thanks, Bob K.

A #12 drill/reamer is 0.190 so it should fit all AN3 bolts...

Skip the 3/16 drill/reamer which is 0.1875...