To make clear headlight lenses, especially for brass models that came unpainted, this is an old custom painter's trick.
Fixture a piece of thick brass or block brass on your drillpress. I'm using my old Unimat mill, but a decent drillpress will work just as well.
This will become a die or die-plate after you drill a hole in it that is the diameter of the lenses you need.
Once you've drill through, do not disturb the set-up. You want the die to remain exactly where it is with respect to the drill-bit and chuck.
Unchuck the bit, take a file, and file the shank-end flat with nice clean sharp edges. The flat should ideally be at a little off-axis of the bit.
Re-chuck the bit backwards, and it becomes the punch. With the motor off and using the quill handle to press through the die or die-plate you made with that same drill-bit, stamp out a supply of lenses from acetate sheet. I often use reasonably thick clear packaging, the stuff that is a pain to get open.
The flat on the shank end of the bit won't affect the function of the bit as a drill-bit, so put it back in your drill index when you're done.
The plastic aircraft modellers have something called canopy cement, not only the thing for putting these in place but also for putting the glazing in cab window openings on brass, plastic, &c.
