Rufus, When I get out your way, I want a lesson in HOW to keep a tap threading straight with a 10” crescent. :exclamation: If I tried that, there is no telling how the threads would come out but you can bet they wouldn’t look like yours!!
We have been adding some carbon fiber to a light or two here and I was glad to see how you & MRsDNF cover the ends on your wood pieces. That makes a nice look the way you did that.
Nice work… to say the very least. I sure have been enjoying these builds. :+1: THANK YOU!!! TL
It’s the guide tube surrounding both the brass and the tap that keeps it in line. .
Then I spent some time. On the collar. I need to sand the O-ring side to 1.5mm from the O-ring seat. I used a washer as a guide. 
And ground it down close. 
And sanded it. 
The washer had tape on the other side as a shim. 
And I removed that and sanded it some more until I just began to sand the washer. After that I flipped it over, ground and sanded it down to even thickness at about 3.2 mm. Then I reamed the battery tube to fit the switch pill. 
It’s a snug press fit at this point. 
Here’s how it fits between the head and the tube. 
I also reamed the wood tube and sanded it some more. It’s ~26.2 mm now but with a wall thickness of 3 mm I think I can go down to 2.5 mm or less. 
The second was a few mm lower to get a piece for the tail cap, and the third at the other end to size it. Here again after that first cut. 
And how the cut looks. 
The blade is only about a half mm thick so I’ll be able to line up the grain pretty well when I assemble it. Here are all the cut pieces. 
Some sanding took care of that. 
The failed battery tube supplied a piece I will use for the tail cap. 
It’s close to the right size already but also isn’t quite square. 
All of this is under wood and epoxy and not visible but at least it’s now sanded square. 
Here again after filing and sanding the OD’s to match. 
Fritz had asked earlier whether brazing was complete between all the surfaces. Well, not quite. Since these bands were very tight in order to hold the seam shut it probably prevented even wicking of the silver solder. In any case the long seam is fully wetted and that’s the critical one. A few more bits of brass will be added to that little tail piece including a fresh piece of threaded copper. The one in the pic is from last year and not legal to use as part of this build so I only use it for test fitting.
I ran into a problem after brazing the stop collar on the tail end and poor MkII paid the ultimate price. MkIII has since been threaded and the the retaining bands removed. The next stop collar will instead be brazed to a short tube that slips over the battery tube before being brazed in place. That will prevent another unfortunate mischance. At the other end I used a carbide Dremel bit to cut the shelf out of the switch pill. 
Then I reamed it to one continuous ID and brazed a thin tube to fit inside. 
The switch will actually go in the small tube with contacts at either end and slide into the larger threaded piece.