Opinions needed (I know everyone has one!)

[northmn]

I am finding quite a few "givens" that were preached back when are not really given.  Still I do think you can move the lock a little too far forward.

DP

[Dennis Glazener]

Well on this one I positioned the lock too far back. The fence is about a .100 inch behind the breech. Twas a brain cramp, I was too concerned about perfect alignment of the touch hole to the breech. (its about .008 inch in front of breech).

Forgot about the threads for the vent liner!
Dennis

[Jim Cook]

Dennis,
Thank you for your posts they help us new guys.
I would also like to ask if you could post some pictures of the area in question.

Well on this one I positioned the lock too far back. The fence is about a .100 inch behind the breech. Twas a brain cramp, I was too concerned about perfect alignment of the touch hole to the breech. (its about .008 inch in front of breech).

Forgot about the threads for the vent liner!
Dennis

[northmn]

I still would notch the breech and make my own 10-32 vent liner.  I used one of these on my 25 as it is a small bore and I wondered about using a vent liner the same diameter as the bore.  Your 32 is a small bore also.  You should have had a 9/16 square breech plug which would have entered in to your calculations.  My comments on lock placement were more for the larger bores where the breech plug is 3/4 square and they allow for extra for the insert.  All locks are different also.  Hope that was the only brain cramp you had on that build as I have sometimes had a few more than that on a build.  They are the reason some of us can offer suggestions through personal experience.  The 32 barrel should have enough metal so that if you drill carefully you can hit the face of the breech without enlarging the tap hole and then go and v the face to tap in your liner.  You might even try going in with a smaller bit and drilling out the face of the plug and then use the 21 bit at barrel depth to tap it out.  I used a 1/8 or 9/64 drill for the enterior of the vent insert and then I think a 55 for the touch hole.  Small bits require a bit of care to use. The 32 will be a fun little gun when you are finished.

DP
 

[Dennis Glazener]

Dennis,
Thank you for your posts they help us new guys.
I would also like to ask if you could post some pictures of the area in question.

Jim,
Not sure if this photo will help but here it is.


Before I start to inlet an lock I always mark where the touch hole will be. I like the touch hole to be just a few thousandths in front of the face of the breech plug. I start by sticking a ram rod down the bore until it hits the face of the breech plug. I then mark it with a sharp pencil or knife point. Then I transfer this mark onto the outside of the barrel on the flat where the touch hole will be. This tells me where the breech plug face is. I then SHOULD make another mark toward the muzzle that allows the vent liner threads to clear the face of the breech plug. (This is where I had the brain cramp. I failed to allow for the vent liner threads) Then you allow for half the diameter of the touch hole, I usually add .035" to be sure. This should mark the spot where your touch hole should be.

I then lay my lock plate on the stock, centering the pan where the touch hole will go, position it where I want it then using a thin flat ruler I line the center of the pan where it will match up with where I want my touch hole. Make whatever vertical adjustments I need to get the lock plate where I want it (make sure the touch hole will be fairly close to the center of the bore, not too low where the vent liner will be too close to the bottom of the bore). Once I get all this worked out I take a sharp punch and prick (not too deep, in case something happens you can move the touch hole) the barrel so you can see where the touch hole is to go. I then inlet the lock and after it is finished I will install the vent liner and if I did everything right the touch hole threads will be a few thousandths clear of the
breech face. The touch hole in the photo looks a little off but its dead center perfect, just too close to put a vent liner in without part of it being in the threads of the breech plug.

I don't worry about where the fence of the lock ends up in relation to the breech.
In my case the fence ended up being behind the breech by about .110.
Hope this helps and I didn't confuse you. Others may do it differently but this USUALLY works for me!
Dennis

[Jim Cook]

Thanks Dennis for both the explanation and the photo.
Your note will be printed and put in my notebook.

[northmn]

I do not know where I have picked up some of the "standards" and could not quote them because a lot of them are dated back about 20 years.  Some were from old Muzzle Blasts magazines and some from other builders I associated with.  The interaction on this site has been valuable in learning new techniques and other pointers.  Mostly I had installed locks similar to what Dennis had stated, but usually placed them so the touch hole would ignite the base of the charge, another given.  Then I would work out the face of the breech plug and even thread part of it for the vent insert.  Why put the vent at the base of the charge   I was told it gave faster ignition   Interesting isn't it how we sometimes pick up these "standards".  They have been making "square breechplugs since BC.  Colerain used to use a .55 long plug, whether they still do I don't know.  These tend to place the lock more back on the build.  Others use the square system where a 9/16 plug is 9/16 long and a 3/4 is 3/4 long.  I have sawed off the breech or cuped the face of plugs to get the lock placed farther back.  Probably not needed. 

DP