Serrated knife sharpening wheel

[3D Anvil]

Plus I realized afterwards that a serration is not a half-circle, but rather a portion of it, so the diameter can be wider than the pitch.
...snip...

A radius gauge set, like below is the right tool to measure the serrations. Match the curvature of the gauge to any portion of a internal or external radius and read the measurement from the stamped markings. 

Thanks!

[3D Anvil]

So until now I've been getting by on bread knife sharpening by ... not really sharpening, but by using the SchleifJunkies' "leather wheel for serrations" and the edge of a belt to strop serrations.  I was using 1 micron diamond on the wheel and PA-70 on the belt.  Worked okay, but not really satisfactory for a dull knife.

This morning I leveled it up, using 20 micron diamond on the wheel, and I'm pretty happy with the result!  I was sharpening a Mercer bread knife with roughly 1/4" serrations.  Before sharpening, it measured at around 300 BESS.

I did 3-4 passes on the bevel side at the measured edge angle (25°) and then stropped on the edge of a leather belt with PA-70.  That got my BESS reading down to 110-125g, which to me is more than acceptable for a bread knife.

Now, I don't know how it would work with a really dull knife, and it's obviously not going to restore a knife with rounded points, but that's a topic for another day.

https://schleifjunkies.de/en/product/leather-wheel-for-serrated-edge/