Do the aperture disks for Lyman receiver sights (like the Lyman 48 or 57) also fit other types of sights (like tang sights)? I'm wondering if there is a universal thread size for the aperture disks or if each make of sight has it's own thread.

If memory serves the 7/32x40 thread is used on Lyman site disks. Frank

There is somebody on Ebay that lists aperture discs only in the gun parts section of Ebay. I think I was looking for an aperture sight for my Marlin 1894. If I recall correctly, $12-$15 bucks will do it.