Thread ID?s

[WestKentucky]

I have acquired a couple “parts kits” for RG10 revolvers. I don’t intend to use anything but the barrels and possibly hammers and springs in a scratch build from a pile of scrap metal. I can’t ID the thread for certain though.

Metric thread gauge fits perfectly At 0.75 but the external dimension for the threads is 10.06 mm which is slightly oversized for a 10mm 0.75 fine thread does anybody have an idea? Should I just go with a 10mm 0.75 tap and hope for the best? That seems the closest thing I can find. Maybe the barrel was meant to be a crush-fit in those old zinc framed revolvers?

 

[MihiT]

Mic your tap. You will need clearance at the root of the thread or it won't do it's job.
Try spinnng your die on to it by hand, if that goes then you should be OK.
Spin it up and you could probably knock that 0.03 off with a file.

 

[WestKentucky]

Mic your tap. You will need clearance at the root of the thread or it won't do it's job.
Try spinnng your die on to it by hand, if that goes then you should be OK.
Spin it up and you could probably knock that 0.03 off with a file.

That’s one size I don’t have either tap or die of as of yet. I went ahead and ordered a 3 piece set, taper tap, bottoming tap, and die. I figure if nothing else I can do exactly what you said, spin it and remove the extra few thousandths then clean up the threads in the die. That should be the only metric thing in this gun... I hate metric.

 

[MihiT]

Are you sure it's not a 3/8x34 tpi or something?
Looking at my chart 13/32 comes out at 10.319...

 

[RMH]

Amazon has a cheap SAE/Metric thread pitch gauge for $11.67. This should give you the answer.

https://www.amazon.com/Grip-Thread-Pitch-Gauge-SAE/dp/B004ROIU2A

 

[WestKentucky]

Amazon has a cheap SAE/Metric thread pitch gauge for $11.67. This should give you the answer.

https://www.amazon.com/Grip-Thread-Pitch-Gauge-SAE/dp/B004ROIU2A

I have thread pitch guages. It’s a perfect fit on .75. I checked thread guages for standard as well and the one that was close was clearly still not exactly right.

 

[MachIVshooter]

You need to keep in mind that diameter and pitch combinations on gun parts often conform to part dimensions rather than any standard unified or metric combination. It may very well be 10.6mm because that's how the drawings were. It may be M11x.75 with blunted crests. It may be a 1.5mm pitch double lead. It may not even be a standard 60° thread.