With the 1mm drill bit broken off flush in the aperture...
there was really nothing to do but drill it out with a solid carbide bit. Now the aperture had a giant hole. Lots of light! No sweat. I'll plug the hole and try again.
I opened the hole up a a little more with a #3 bit (my tapping size) and tapped the hole 1/4"-28.
Faced off a scrap of 0.250" diameter acetal (aka: delrin).
Cut a screwdriver slot.
threaded the outside 1/4"-28.
Chopped off a small section. Click the picture to enlarge it and it's easy to see the 1/4"-28 threads in the aperture disc.
A screwdriver from the front threads the acetal into the aperture. And I'm back to where I started before breaking the bit.
The acetal is in really snug and barely stands proud. It's not going to move under recoil so I don't have to worry about it vibrating out.
Faced off the acetal.
Spotted.
Lets try this again. Found another 1mm drill bit and through drilled the plastic plug.
The soft acetal was easy on the bit. Made a second pass at a faster speed. Wanted the hole as round as possible.
Blackened the face of the aperture with some Birchwood Casey Aluminum Black to minimize reflection/glare.
Blackened the inside of the through hole as well.
Test fitting.
Eye shade
All the clearances look fine. I'll paint the outside of the aperture.
A second piece of the threaded acetal rod was cut off, faced, slotted and spotted...
And through-drilled with a 1.2mm drill bit.
So, I screwed up, but ended up with a dead simple aperture with two interchangeable inserts. A 1mm and a 1.2mm.
Final shot. Wow, look at the size of that 10 ring! Just realized that these must be pretty old targets, as the scoring rings were downsized years ago.
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