How do you cut a breech plug without messing up the threads? I was thinking of maybe spinning a die onto the threads first and then spinning it off after the cut. Will this work or is there a better way?
Cutting a Breech Plug
- Thread starter JRBCo.
- Start date
Help Support Muzzleloading Forum:
Phil Coffins
69 Cal.
I use a piece of metal that is turned round then drilled and tapped in the same set up. Then the pug is turned into it and chucked up for working on.
user 34300
54 Cal.
- Joined
- Nov 25, 2019
- Messages
- 1,743
- Reaction score
- 2,124
I use a milling machine. A file works.
Metalshaper
40 Cal.
- Joined
- Jul 6, 2004
- Messages
- 479
- Reaction score
- 132
find one of the thinner 'lock nuts' in the right thread/pitch. Cut through one side flat, with a hacksaw.
spin it on to the right depth and tighten on the nut in a vise. ( the cut allows the vise to tighten the nut and lock/hold on the threads )
cut a bit long and file.. Test and re-file if required..
at least that's what I have done.. my lil X2 mill does a nice job also!
Respect Always
Metalshaper/Jonathan
spin it on to the right depth and tighten on the nut in a vise. ( the cut allows the vise to tighten the nut and lock/hold on the threads )
cut a bit long and file.. Test and re-file if required..
at least that's what I have done.. my lil X2 mill does a nice job also!
Respect Always
Metalshaper/Jonathan
- Joined
- Aug 27, 2004
- Messages
- 3,239
- Reaction score
- 7,174
I am not a machinist by a long shot, but there is nothing wrong with your idea. For smaller threads, (a bolt) I just put a nut on and remove after the cut. A die and a file to cut the sharp edge is just fine IMO. If you have a tang on the plug already and are going to cut the face, I would be more concerned about making a perfect cut than messing up the threads.
Larry
The tang and thread are all one. The plug threads are a little too long and doesn't allow the plug to seat against the barrel. There is about a 3/16" gap.
There are many ways to do it and others here have stated their preferences and all work - it will depend on what equipment you have, your skill level, and what level of accuracy you are looking for. For most of my work on breach plugs I use a file when I only have to remove 1/16" or less if more removal is need then I use the lathe or the mill.
- Joined
- Aug 27, 2004
- Messages
- 3,239
- Reaction score
- 7,174
3/16" will be tough to cut with a hacksaw. If you do not have access to a lathe or mill, then you can grind and file, using permatex blue fitting paste. That is what I do, but then I am not a master machinist, nore have a lathe. For a non skilled person (don't have a clue your skill level) it is almost impossible to obtain a tang/barrel fit combined with the breech plug face bottoming out (and fitting) the counterbore step where the bore and rifling start.
Larry
Flintlockar, I have a fully equipped shop for building knives, hatchets, etc.. However I do not have a metal lathe or mill. I was thinking that I could cut plug about a 1/32" long and then grind off as needed to get right seat and alignment. I would use 5/8"x18 die as guide and then spin off after cut. Would it work though is the big question?
Try to avoid using your die.
It's very hard which also means it's very brittle and the cutting edges like to break just because they can...
A mis-stroke with the file could mean having to by another die.
Metalshaper is offering a good approach or you could try the jam-nut method. Two nuts on top of each other on the breech plug- the first (top)acts as a file stop, the second (bottom) is tightened back against the first to jam/lock it in place.
Good luck!
It's very hard which also means it's very brittle and the cutting edges like to break just because they can...
A mis-stroke with the file could mean having to by another die.
Metalshaper is offering a good approach or you could try the jam-nut method. Two nuts on top of each other on the breech plug- the first (top)acts as a file stop, the second (bottom) is tightened back against the first to jam/lock it in place.
Good luck!
ppb, I think I will try a combination of the jamb nut as per Metalshaper and spin the die as far back as possible so when I make the cut I can remove the jamb nut and follow it up with the die so that I get nice clean threads. Sounds like I'm over complicating this though. I guess I will find out. Thanks everyone.
Using a jam nut is going to be tough to do as the thickness of one 5/8" standard nut is over 1/2". so HOW are you going to get TWO nuts on that breach plug to jam them together 
???? Here are other sizes of steel nuts so you can get the REAL picture of what is going on < Nut Dimensions — Baden Steelbar & Bolt Corp. >. Using a die is a good idea IF the die is thinner than the breach plug threads and no you will not damage the die as the starting thread of the die is recessed - if you can hit that first thread then you should not be touching this type of work
.
???? Here are other sizes of steel nuts so you can get the REAL picture of what is going on < Nut Dimensions — Baden Steelbar & Bolt Corp. >. Using a die is a good idea IF the die is thinner than the breach plug threads and no you will not damage the die as the starting thread of the die is recessed - if you can hit that first thread then you should not be touching this type of work.Metalshaper
40 Cal.
- Joined
- Jul 6, 2004
- Messages
- 479
- Reaction score
- 132
Zugg,
you only use ONE jam nut. The slice through the flat ( as I described ) and clamping in the vise is what holds/Locks things in place for cutting and filing.
I consider the jam nut as somewhat sacrificial.. in that I'm not that worried if it gets a lil scratched and such as you are using it.
when you turn the nut back off, it clears the burs on the thread ends. a lil touch up filing and you are done?? Hopefully
Respect Always
Metalshaper/Jonathan
you only use ONE jam nut. The slice through the flat ( as I described ) and clamping in the vise is what holds/Locks things in place for cutting and filing.
I consider the jam nut as somewhat sacrificial.. in that I'm not that worried if it gets a lil scratched and such as you are using it.
when you turn the nut back off, it clears the burs on the thread ends. a lil touch up filing and you are done?? Hopefully
Respect Always
Metalshaper/Jonathan
That should work --Zugg,
you only use ONE jam nut. The slice through the flat ( as I described ) and clamping in the vise is what holds/Locks things in place for cutting and filing.
I consider the jam nut as somewhat sacrificial.. in that I'm not that worried if it gets a lil scratched and such as you are using it.
when you turn the nut back off, it clears the burs on the thread ends. a lil touch up filing and you are done?? Hopefully
Respect Always
Metalshaper/Jonathan
. To my way of thinking a "jam nut" would mean two nuts jammed together but I could see where it could be taken as one nut run down to a shoulder as in this case
Metalshaper
40 Cal.
- Joined
- Jul 6, 2004
- Messages
- 479
- Reaction score
- 132
Your welcome Zugg!
although I have some plugs with a long threaded journal. The jam nut, threaded to the shoulder would mean the cut was wrong.( too short ) I "try"
to measure and just turn the jam nut in far enough?? then cut and file. but there are variations to the theme
Respect Always
Metalshaper/Jonathan
although I have some plugs with a long threaded journal. The jam nut, threaded to the shoulder would mean the cut was wrong.( too short ) I "try"
to measure and just turn the jam nut in far enough?? then cut and file. but there are variations to the theme
Respect Always
Metalshaper/Jonathan
- Joined
- Aug 27, 2004
- Messages
- 3,239
- Reaction score
- 7,174
Your approach sounds like a workable one to me! Since it is such a short cut, I would grind it all and forget the die. Before you start, if you haven't already, make sure the counter bore shoulder is at 90 deg to the bore. It should be, but make sure it is. If it isn't that of course will really affect the fitting/fit. Dial calipers can do that for you. You did not say, but I assume this is on a round barrel??? If it is octagon, then you are also going to have to consider timing for the tang to coincide with a flat.
Larry
Larry, The counter bore shoulder is 90 deg. and yes it is octagon. Will take it slow and easy.
HighUintas
45 Cal.
- Joined
- Jan 11, 2022
- Messages
- 514
- Reaction score
- 577
We're you able to successfully get your plug cut using metal shapers nut method?
I am currently facing the same hurdle. My plug is about 1/4" too long and plan to use the nut in the vice method. Filing 1/4" off seems like it would take quite awhile
Clamp it in a vise using the split nut method and get on it with a side grinder until you get close enough to use a file to finish up.
breech plugs are soft, a good sharp file will make quick work of it.
Similar threads
