Gun/bomb sight or HUD optics

[STM]

Most kits do not come with clear parts for the optics in gun/bomb sight or HUDs. They are actually pretty easy to make and add another dimension to the realism of your cockpit, especially in 1/32 and larger scale.

To begin with, I never toss clear sprue from a kit once it is complete. It comes in handy for any number of things. To begin, you may have to drill out the are in the sight with a drill bit. I highly encourage using a carbide bit as they drill a much cleaner hole. Using a pair of digital calipers, a vital accessory that should be on every modeler's bench, and measure the diameter of the hole you drilled. I then cut off a small piece of sprue, larger than the hold I drilled, and place it into the chuck of the Dremel. I use microfiles and reduce the diameter of the piece of sprue, checking frequently with the calipers, until it is the same size or maybe a couple of thousands of an inch smaller, then the hole you drilled. 

Once you have done this, while turning the sprue in the Dremel at the lowest seed, use a flat file and rough out a rounded shape to the piece of sprue. I use Testors sanding films, from medium to extra fine when I do this. Once I am finished, I take another Dremel (you all have at least 2, right?) with a polishing wheel and some polishing compound. I find what works best for me is Turtle Wax polishing compound you can get at any auto parts store. A tub is enough to last 2 lifetimes. Wet the polishing wheel and put on the polishing compound and polish the rounded part of the sprue until it is perfectly smooth. I then take a razor saw and cut off the rounded part, so the piece of sprue is at least 1mm long. I then take the flattened end and run it along the sanding films until it is very smooth and there are no blade marks. You will be dealing with a very small part indeed, so for the finishing polishing step, I usually stick it rounded edge down on a piece of duct tape, which is very sticky, and using the same polishing procedure, polish it smooth. If you really want to get anal, you could dip it in Future but I have never found that necessary. Since all modern jet optics are optically coated, I often put a little bit of Tamiya clear green on the flat size of the "lens". Let it dry thoroughly and very carefully cement it into the hole. White glue may be better than CA since it will not craze the piece of plastic.