Breech plug install

[romoshka]

Ok, so I’m the fool (see Parts and instruction thread) who’s going to complete this Ky pistol. So you can see the breech plug is hand tight but lacks a few degrees of rotation to be aligned. I will assume that vise and wrench will solve this but my machinist education tells me I should add some thread locker. Another additional option I see is to drill and tap the underside for a set screw with small brass plug against the threads. What say the more experienced builders here?

 

[Phil Coffins]

Use no thread locker. I don’t use anything on breech threads at all. Toque to aline then put a witness mark on the underside.

 

[ronaldrothb49]

You actually need to do the exact opposite. You need to put an anti seize grease on the threads. There is more to properly installing a breech plug then just screwing it into the barrel. You need to have the face of the breech plug mate up with the end of the bore sealing it at the same time that the tang on the breech plug mates up with the top flat of the barrel.

 

[SDSmlf]

View attachment 368941
Ok, so I’m the fool (see Parts and instruction thread) who’s going to complete this Ky pistol. So you can see the breech plug is hand tight but lacks a few degrees of rotation to be aligned. I will assume that vise and wrench will solve this but my machinist education tells me I should add some thread locker. Another additional option I see is to drill and tap the underside for a set screw with small brass plug against the threads. What say the more experienced builders here?

Big NO to the thread locker, rather time for some sort of anti seize.

Is the front of the breach plug bottomed out in the barrel? Guessing with your machinist education you were taught to use something like Prussian Blue to confirm fit. Also, loose the setscrew idea.

And not that it matters, but went through a Tool Maker apprenticeship years ago.

 

[Phil Coffins]

Having a good fit and clean machining of parts are all that’s needed. All though I am a hobbyist now my back ground has formed my process of fitting things together. After gunsmith school I worked with one of my instructors building custom ordered Sharps rifles. Opportunities changed and I became a tool maker for a major manufacturer for fifteen years. Then moved and did most of the manual machine work for a company that built race cars from the ground up for ten years. Many people that have tinkered at home have developed all sorts of short cuts and well meaning ideas about what they like to do. Most of it is un-nessasary and harmless as long as they do the basic good work to start with.

 

[ChuckJonesWagon]

My only question that your pic doesn't show is, is the breech plug fully seated in the chamber inside the barrel?

When I fit a breech plug I use a transfer agent to make sure the plug is tight agains the inside chamfer that the drill left.

 

[Eric Krewson]

Timing a breech plug can be a tedious job, some that are good at measuring can take measurements and know a ball park figure of how much metal to take off the barrel and the plug to bottom out the plug in the breech and line up the top flat at the same time.

My system is to work on the plug and barrel a little at a time until I get the plug bottomed out and any barrel flat lined up as well as a seamless gap where the barrel and tang meet. Most of the time it is the top flat but if I get a perfect fit on another flat I go with it. I like to fit my plugs so they are finger tight to within 1/2 flat of lining up and bottom out perfectly with only 1/2 flat or less of wrench work and around 25 ft lbs of torque.

I didn't watch all of this but suspect it will explain how to correctly install a breech plug.

 

[romoshka]

Timing a breech plug can be a tedious job, some that are good at measuring can take measurements and know a ball park figure of how much metal to take off the barrel and the plug to bottom out the plug in the breech and line up the top flat at the same time.

My system is to work on the plug and barrel a little at a time until I get the plug bottomed out and any barrel flat lined up as well as a seamless gap where the barrel and tang meet. Most of the time it is the top flat but if I get a perfect fit on another flat I go with it. I like to fit my plugs so they are finger tight to within 1/2 flat of lining up and bottom out perfectly with only 1/2 flat or less of wrench work and around 25 ft lbs of torque.

I didn't watch all of this but suspect it will explain how to correctly install a breech plug.

Wow, thanks. That was indeed very helpful. As a super green (read ignorant as a box of rocks) I had no idea that the breech plug was to seat on an an internal land. Now with a bit more study I grasp the concept. I have a little metrology section in my home machine shop and it looks like I’m 0.145 off the seat. While I fully appreciate the craftsmanship of this fellow with a file I’ll be relying on my mill. Also as I begin to think about the initial manufacturing process as well as correction and fitment I found this video that explains manufactingberrors as well as 1 remedy method.

 

[romoshka]

Having a good fit and clean machining of parts are all that’s needed. All though I am a hobbyist now my back ground has formed my process of fitting things together. After gunsmith school I worked with one of my instructors building custom ordered Sharps rifles. Opportunities changed and I became a tool maker for a major manufacturer for fifteen years. Then moved and did most of the manual machine work for a company that built race cars from the ground up for ten years. Many people that have tinkered at home have developed all sorts of short cuts and well meaning ideas about what they like to do. Most of it is un-nessasary and harmless as long as they do the basic good work to start with.

You sound like a most interesting fellow.