The cap to my spotting scope broke several years. Bushnell couldn't determine a part number without the old one. I recently decided to make one, but I was a bit apprehensive about an internal metric thread. I found an article about changing the gears and forged ahead. The thread on my scope measured about 41-1/2 mm diameter. I bought some aluminum discs for threading practice. My second trial fit a bit loose, so I tried 1.610" bore, which worked very well. Feeding .030 on compound. I didn't want it too bulky, so I added a step and a half inch chamfer.
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