Monday, November 22, 2010

Anti-Glare Tube for a HW Front Sight

Haven't had a lot of time to tinker lately, but a short session outside with sunshine and aperture sights left me wanting less glare on the front sight. Target shooters have, for generations, used extension tubes both front and rear on aperture sights to reduce side light.

As I have a few guns with HW foresights, it made the most sense to make a tube for that model.

Uh, anybody got a M17 x 0.5mm threading die? Yeah, me neither. The guys at Kromhard usually ask "What in hell is that for?" whenever I come looking for a tap or die. Of course, they had a couple in stock but nobody could remember ever selling one before. Well, non-standard is the standard in airguns and firearms. At least I wasn't looking for a die for a rear Anschutz aperture. I think they're a half size--something like M9.5 x 1mm. And don't even start with the BSF thread sizes and what's with some of the Italian sizes that blend metric diameters with threads per inch??? Makes some of these almost sound "normal".

Started with a scrap of recycled aluminum. It's from a broken suspension seatpost for a bicycle. Nice. My project is green!

I hacksawed the ends off and came up with a piece about 2.5" long. OAL is not at all critical and I still haven't bothered to measure it. Mounted a steady rest and faced both ends. Not shown: center drilled each end to fit a live center.

Live center in use. I really just want to make a stretched version of the HW tube. I can't find a common term for the piece. Centra calls it an "eye cup ring". Anschutz calls it an "extension tube". Whatever. I turned the center down to about 15.2mm dia.

Left a 17mm diameter ring near the front for those fine threads. Cut the relief at the front of the tube to bear against the aperture insert.

Progressively through-drilled. Took the hole up to 1/2"--about 13mm.

That's a lot of shavings.

This is where it got tricky--and I'm not real proud of this set-up--but it worked. I didn't have a 1.5" die holder for the tail stock and I didn't feel like making one. Did have a 90 degree slotted angle plate, so I bolted it down to the crosslide and squared it up with the tube.

Started with just the round die sandwiched between the angle plate and the tube. The chamfer on the die centered up the thread and pressure on the crosslide kept the die perpendicular. After three or four full turns by hand (fine threads need very low torque) I added the die holder for a bit more leverage.

Another couple turns and I backed off the crosslide and angle plate and just rotated the lathe chuck by hand holding the die stationary.

My knurling tool won't quite adjust large enough to handle the end ring. I'll knurl it in the future if/when the opportunity presents itself.

A little flat black color and the glare is banished.

Mounted it up on the IZH-61. Since I've been shooting this gun for a while now, there's a few other things I want to tweak in the near future.