Repair to Lock plate

[Jerry V Lape]

I have a very nice custom lock, engraved professionally and finished bright, which has the front lock bolt hole drilled in the wrong location. (It was drilled for a different barrel/stock).  I need to plug that hole and drill a new hole which very likely will intersect about a 1/3 of the old hole.  I was thinking to silver solder a bolt piece into the hole but have a couple concerns.  What happens to the bright finish during the soldering process (the engraving stops about a full inch from the hole so I wanted some advice about a heat sink between the hole and the engraved area) and will the silver solder hold up to the drill and tap work? 

Or is there a better solution?

[Mike Brooks]

I have soft soldered in situations like that with no problems. Just polish over the engraving, it won't hurt it unless you get crazy....

[jerrywh]

 When you say silver solder do you mean high temp[1275° or low temp silver 450°?

If you use high temp you will need to use some sort of heat blocking to protect the engraved part. You could accomplish this by clamping the plate in a vise or a clamp of some type that will act as a heat sink. The main thing is to stop the oxidization from forming on the engraved part as you have already indicated. The ideal method is to tig weld it. I have tig welded holes like that and kept the oxide no further than 3/8" from the hole. The heat stop that is sold for that purpose works well if the heat is not applied for too long of a period of time. If you have some sheet copper you could put a piece between the clamp and the plate to protect the plate and act as a heat sink also. The more massive the clamp the better it will work.

[James Wilson Everett]

Inserting a properly threaded section into the hole and then riveting the ends will do the job without the solder line.  If properly done the interface may be less obvious than solder.  Here is a photo of an original lockplate with lots of riveted holes.  This one has had a long history, for sure.

Jim

[Keb]

Plugging it with a screw will work and it will possibly be hidden behind the spring. I've done it many times but I'm a horrible hack.

[davec2]

If the new hole will not intrude into the plug more than a third of a diameter, I would do a cold plug by putting a very slight chamfer on both sides of the plate, installing a threaded section of a soft steel screw (protruding a little on both sides), peening (riveting) the plug, and then finish off the remaining steel flush on both sides and polish as necessary.  However, if the new hole will cut to the middle of the old one, it would be best to use some of the lower temperature silver bearing solders (Brownells Hi_Force 44, or equivalent) to keep the threaded plug in place while the new hole is drilled and tapped.  If the plug is not soldered, and you overlap the old and new holes by close to half a diameter, you will likely spin the threaded plug out of the original hole.  The Hi-Force 44 solder runs at ~ 650 to 700 degrees, so oxidation should not be a problem for a quick solder job and the heat discoloration should polish right back off the plate.  For higher temperature soldering (or case hardening) I often coat the part I want to protect from pitting or oxidation with this:

http://www.brownells.com/gunsmith-tools-supplies/metal-prep-coloring/heat-treating-accessories/anti-scale-coating-prod23076.aspx

It paints easily on the steel surface and protects it from atmospheric oxygen while you do hot work.  When I need to re-harden a frizzen after engraving, this will keep the engraved surface very clean during the heat and quench.  Also good for heat treating knife blades that are near their final surface finish.

[jerrywh]

 If you use high force 44 as Dave suggests I suggest you use the flux that is made for the high force 44. Browne has it also. Like Dave says be careful that  the new hole doesn't go very far into the plug because at times it will spin the plug and lock up the tap.
 If you can't find the anti scale flux you can use sodium silicate. Walmart should have it.

[Jerry V Lape]

I have Brownell's 44 high force low temp with their flux.  They are out of the anti scale but I have some time yet.  Really appreciate all of your help. Great thing about this forum is that the professionals are so generous with their experience.

One more question.  I am used to tinning surfaces but not sure how to do that with the threaded surfaces.  How do I go about that.  If I tin and wipe each surface should there be enough clearance to allow threading them together and reheat?  Or should I just flux the surfaces, screw together, heat and expect the solder to flow through the threads following the flux.   

[davec2]

Jerry V,

With the female threads clean and the plug clean (i.e NO oil, rust, anything but clean metal), flux the hole and the plug.  Screw the plug into place.  Heat gently from the outside of the plate and apply the solder to the back side.  Solder will always flow toward the heat, so as soon as the solder melts it will wick nicely through all the threads.  I would not tin either part, but heat slowly.  You do not want the flux on the outside of the plate to overheat and burn before the backside gets to the melting temp of the solder.  I would drill and tap a piece of scrap plate about the same thickness as the lock plate, make up a couple of plugs, and practice soldering the joint before attempting the lock plate.

[andy49]

You could rivet a screw in the existing hole then solder a small bolster on the back of the plate then tap with a dead end tap for the lock bolt. This way you can avoid drilling thru the rivet.
Andy

[jerrywh]

Andy49
 has a good idea. You can make an offset lug with a thread to match the existing hole.
 That way you won't have to solder at all.  Good thinking Andy.

[Jerry V Lape]

I was planning on  several practice runs before doing the lock plate.  Have to contemplate the bolster idea, certainly an attractive option.  Also considered using a hook front fastener as is fairly common in English guns.  I am going to  practice that one as well and see how I like it. 

Thanks again for the experienced advice. 

[JTR]

Keep in mind that if you solder it, the solder line is going to show. It might be small, but it will show.
John

[Pete G.]

  Also considered using a hook front fastener as is fairly common in English guns.  I am going to  practice that one as well and see how I like it. 

Thanks again for the experienced advice. 

That would be my first choice. Use the existing hole to thread the hook to the plate. Then it will look like that is what you planned all along.

[Jerry V Lape]

Pete G.  I like that solution too but the lock is similar in size to a small Siler except the main spring only leaves 9/32 " forward of the spring to the end of the lockplate.  Have to leave at least 1/64 for clearance with the spring so my work space is pretty tight.  I am going to set up a practice piece and see how that goes with a practice inlet so I get all these little parts working right before putting them on the real lock plate.  Lot for me to learn yet.  But that is the fun part of building isn't it.  If I like this solution I may use it again as I really dislike fishing the front lock bolt through the skinny webs. 

[Curt Larsen]

I've done this several times and I plug the misdrilled hole with a short section of screw and peened it in to expand it into the threads.  Then I simply file it smooth.  It hardly shows and will take browning etc.  I think the solder joint will show.  I've done this on a couple of locks, but mostly on tangs where the holes are a bit off center.  I'm generally more careful now, but still slip up now and then.
Curt