Gunsmithing Measuting a dovetail to get the right cutter

[Romeo458]

Him playing around with a black powder revolver and I want to shorten the barrel. I need to find the right bit to cut the load lever retainer. How do you measure these. It's the same type you would do for a rear sight on a handgun but I don't know how to measure those.

 

[sjmpcc022]

Larger dovetails you can measure with gauge pins. With a small one such as that find someone with a comparator that could measure it for you.

 

[lariat]

You can back into the answer by removing the lever retainer and measuring the angle on it. It’s all a triangle. That’s the piece you want to match anyway.

 

[iceng]

A good cheats way is to knock out the dove tail and then measure the sight (or lock in this case). It will probably be 60 or 65deg.

As for the width of cut, just get a smaller one and step it side to side slowly slowly until you can make it fit. If the sight is 0.400" wide, a .330" cutter will work a treat. Run an end mill thru first to remove the bulk, then get the .330 in there, and move 0.035" one side then the other for a total of 0.070", which should make the dovetail size you need.

It's a safer method to go perhaps 0.030" each side, and slowly increase it and keep checking to make it a nice tight fit and not stupid sloppy.

 

[Steel head]

 

[skl1]

Also, be aware that while we have 3/8" (.375) dovetails on lots of slots, often European (Uberti/Pietta) slots will be 9mm (.355'ish), so be careful not to buy a 3/8", 60 degree cutter and overcut the slot. You can cut it undersize with the endmill and file it in if you have trouble finding the right cutter.

 

[Romeo458]

I'm taking about 4 inches off the barrel so I have room to practice. Thanks for the tip on metric sizing. That would make sense since it's an Italian copy.

 

[iceng]

If you have a spare piece of alloy rod, do a practice cut to confirm.