benEzra
Moderator Emeritus
by breaking off the handle and shaft of the rotary on/off switch.
I was getting my gear together for a carbine match at the time, but at least it happened at home. And fortunately, I was able to fix it, and figured out how to prevent it in the first place.
Here's the sight. The on/off switch is the one just behind the lens on the right side of the sight.
The switch had always been a bit tight, but it had been getting progressively harder to turn over time, and last week the shaft failed from metal fatigue and the on/off switch handle came off in my hand.
After finding that Tantal doesn't carry any replacement switch parts (darn), I took the side plate off, and found that the on-off switch merely spins a cam that operates the actual on/off switch via a lever. The cam was frozen solid to the receiver; there was no visible corrosion, but there must have been some surface oxidation of the cam or something that triggered the freezup.
I reamed out the switch shaft hole a little until the cam turns freely, lubricated and reattached the handle to the cam and remaining part of the switch shaft with a longer screw, and it now works again. Unfortunately, the spring-loaded detent ball flew across my garage when the handle first came off (haven't found it yet, it's tiny) but the switch works fine and holds position without it.
Moral of the story is, if your on/off switch gets hard to turn, take off the sideplate, detach the cam from the switch handle (carefully, over a towel, don't lose the detent from the handle) by unscrewing the shaft screw with a fine hollow-ground screwdriver, and lubricate the bearing surfaces of the cam and switch plate with a teeny bit of gun grease or synthetic oil (and clean up the switch shaft hole if necessary). If you let it get too hard to turn, you can fatigue and eventually break the shaft.
I was getting my gear together for a carbine match at the time, but at least it happened at home. And fortunately, I was able to fix it, and figured out how to prevent it in the first place.
Here's the sight. The on/off switch is the one just behind the lens on the right side of the sight.
The switch had always been a bit tight, but it had been getting progressively harder to turn over time, and last week the shaft failed from metal fatigue and the on/off switch handle came off in my hand.
After finding that Tantal doesn't carry any replacement switch parts (darn), I took the side plate off, and found that the on-off switch merely spins a cam that operates the actual on/off switch via a lever. The cam was frozen solid to the receiver; there was no visible corrosion, but there must have been some surface oxidation of the cam or something that triggered the freezup.
I reamed out the switch shaft hole a little until the cam turns freely, lubricated and reattached the handle to the cam and remaining part of the switch shaft with a longer screw, and it now works again. Unfortunately, the spring-loaded detent ball flew across my garage when the handle first came off (haven't found it yet, it's tiny) but the switch works fine and holds position without it.
Moral of the story is, if your on/off switch gets hard to turn, take off the sideplate, detach the cam from the switch handle (carefully, over a towel, don't lose the detent from the handle) by unscrewing the shaft screw with a fine hollow-ground screwdriver, and lubricate the bearing surfaces of the cam and switch plate with a teeny bit of gun grease or synthetic oil (and clean up the switch shaft hole if necessary). If you let it get too hard to turn, you can fatigue and eventually break the shaft.
