Sunday, May 9, 2010

A Weihrauch Rear Sight Screw for Alan

Airgun buddy, Alan, accidentally damaged the rear sight attachment screw on his new Weihrauch 30S and has been unable to obtain a replacement. A plea to HW Germany was unsuccessful, so I sent him the bolt from my Beeman R1. Unfortunately, it proved to be 2mm too short and Alan was stuck with a new gun he couldn't shoot. Remembering my annoyance at having to use threaded bushings when making a sight cover plate for my HW35E, I elected to obtain a thread cutting die and just make him a new screw.

The screw is an M5 x 0.5mm and it's such a bizarre pitch size it's difficult to find a thread cutting die in the US. I did locate one on the net, but it was $39--that's about 4 times what 1" diameter thread cutting dies sell for.

Of course, my favorite machine tool supply company, Kromehard Twist Drill, had a small box full of them for about $10 each.

Die shown with a too-short-for-Alan HW rear sight screw.

Just a pic for scale. Pretty small screw.

Cut off a piece of 3/8" O-1 tool steel.

Bored the jaws and chucked the stock. Turned the end down to 4.90mm. Put a slight taper on the end to ease the start of the threading die.

Liberal application of cutting oil and the die cut the threads effortlessly. Fine pitch threads are a dream to cut due to the low torque needed to advance the cutting tool.

Cut and faced the end down leaving 7mm of thread to the underside of the head.

The HW screw has a 9mm diameter head. The 3/8" diameter drill rod equates to 9.525mm.

Another angle

Removed 0.525mm.


Alan didn't want me to waste my day on this, so I cut the slot with the hacksaw, too. Aligned by my green optical guestimating comparators.

Faced and beveled the head of the screw.

I cleaned the threads a final time since it had been in the 3-jaw, but there was no need.

I'll clean it up a bit and cold blue it with Birchwood Casey Perma Blue paste. Alan can polish it out further if he requires it. Looks like a Chapman #93 flat blade bit fits the slot exactly.


Volvo said...


Amazing as usual, every time I read your blog I realize how untalented I am.

derrick38 said...


It took longer to upload the pics and write the captions than to do the job. Nick tackles the hard stuff, I do the fluff.

BG_Farmer said...

Good job. In addition to the hacksaw for making the slot, you can also use a small slotting file. I got a set of cheap Swiss Pattern files for working on longrifles and the like, and they are really handy. Every screw on old rifles was made by hand, which is why they used so many pins:).

By the way, your shop is to my workspace like the Borg Cube is to a space shuttle:).

derrick38 said...


Yeah, I've used various files plenty of times for screw slots. The hacksaw was readily at hand and seemed an appropriate width for the screw head size.

AlanL said...


I know I've said this to you several times in my emails, but let me also thank you publicly on your blog. I am very embarrassed and grateful that you have taken so much time and trouble on my behalf. Your screw looks even better than the original factory screw. Not only did you have to hunt for a special and expensive die but on top of that you made me two screws when the first one turned out too short.

You are a gentleman craftsman of the first order, and I owe you big time! Hope you'll at least let me buy you dinner or something... If you take your family on a cruise and come through Miami let me know!