Not saying that what you have is not a 10-28 screw.
10-28 is not an American Standard Thread but 12-28 is.
The diameter for a #12 screw will be .216
This is how to determine the Number of a screw when the diameter is known.
#10 example
.190 (Diameter of said screw) minus .060 (Standard) = .130
.130 divided by .013 (Standard) = #10 Screw
The distance from thread crest to thread crest for a 28 TPI thread will be .0357
1 divided by 28 (number of threads) = .0357 (pitch)
If you are unable to locate a replacement the next time we are running a #10 screw job we can sneak something in for you.
Dave
http://www.stellarmachine.com/