Amal needle jet gage...

After all these years (40) of owning Nortons, I made a simple gage for measuring the needle jet.
I just polished a steel drill bit shank down to 0.106" measured on a digital caliper. Then I tried the fit on a handful of old jets.

As expected some were a looser fit than others. The metering is done inside the threaded portion of the jet. The gage will not
identify any ovalness to the jet due to the needle if that is an issue.

Is there a wear-out measurement for the needles?

I use a thumb guage on the jet needles. Rub my thumb nail down the side of the needle. If I feel ridges...replace it.

Why not use a .106 plug gauge? I believe you can get then over/under by .0001 or .0002. If you get the one on either side of .106 you can get a pretty good feel for the actual size.

Dave