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Lock from castings

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Ajgall

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I’m about to begin building my first lock from a set of castings. Is it better to clean up and file the castings first or drill and tap the holes before cleaning up and polishing the castings?
 

Phil Coffins

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I’ve done few and the casting need to be filed, polished and fit before drilling and tapping. There’s another tread that a fellow is fighting a store bought lock that is nearly raw castings with poor results, learn from his mistakes.
 

1950DAVE

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I haven't done a kit lock but should I , I would definitely start with getting as much of the coarse work out of the way before any details started. Drilling and tapping are in the details.
Dave
 

Robby

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For sure, all mating surfaces need to be cleaned up first.
Robby
 

rich pierce

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Depending on the castings there are some pitfalls here. The following need very close dimensions: tumbler thickness inside the plate, sear pivot and nose area, and “legs” dimension of the bridle. One cannot simply clean up each item independently without matching their dimensions. It’s best to measure all and see what you’ve got. Then turn bridle down on a lathe till both faces are clean. Capture this dimension and then make the sear pivot area and nose the same dimension. Then the tumbler legs need to be a smidge longer to allow tumbler and sear to pivot. Dave P can do better explaining it.
 

dave_person

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Hi,
The first step is to remove all the sprues and flashing but make sure a sprue is not hiding a detail that needs preserving. A classic example is sometimes the tiny lug on the back of a top jaw that slots into the flint cock is buried in the sprue for the top jaw. The next step is file the inside of the lock plate perfectly flat. Then you can start to see how the parts will fit together and can get them cleaned up and bearing surfaces polished ready for drilling. Do not trust the witness marks on the lock plate. They can be off. Often they are based on the original lock plate. However, cast parts shrink a little during casting so the witness marks may be off a bit.

dave
 

Ajgall

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Thanks for the help I will definitely have to measure to make sure the holes are properly spaced before I drill
 

plmeek

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Ajgall,

You didn't mention what type of lock you are planning on assembling or the source of the castings. As a result you've received some good but pretty general advice. You also don't give any details on the type of tools and equipment that you have available.

There are at least two ways of learning a task or skill. One is trial and error or the "School of Hard Knocks". The other is studying published "how-to's" to learn from them.

A couple of resources in the "how-to" category is John Bivins' article titled "Precision Assembly of Lock Kits" that was originally published in Rifle - The Magazine for Shooters, Jan-Feb 1977 issue #49. Sometimes you can find these old magazines on Ebay. The article was republished in Gunsmithing Tips & Projects. The second edition of this book is available from Track of the Wolf.

An online source that can be helpful if you have access to a lathe and mill or drill press can be found on the ctmuzzleloaders.com website under Building a Manton V-Pan Lock - Part 1 - 3. This example uses a set of castings from The Rifle Shoppe.

These resources show different solutions to a common problem--how to hold the odd shaped parts to machine, file, drill, tap, turn, etc. Bivins shows how to make a "holding jig" that holds the lock plate for drilling, tapping, and reaming holes. He also uses clamps to hold parts such as detachable pans and bridles to the lock plate while it is held in the jig. Bivins jig is designed to be used with a drill press. The guy assembling the Manton lock uses high-temperature shellac to hold parts to brass round stock and brass plate for various operations.

The image below is from Bivins' article showing the tools commonly used. The caption for the picture is below the image.

Tools for Assembling Locks - Bivins001.jpg


Tools for Assembling Locks - Bivins002.jpg
 

Ajgall

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Thank you, you’re correct I omitted so relevant details:
The casting set was from Track of the Wolf I believe (I received it as a gift)
It is for a large Siler lock
I have a drill press and a large assortment of files, taps, dies, and polishing and grinding bits for a rotary tool. I also have a torch for the necessary hardening and tempering
I looked in my copy of The Art of Building the Pennsylvania Longrifle and didn’t see anything other than just basic lock info.

I have the Kit Ravenshear books on metal and woodworking somewhere I’ll need to find.

I’ll have to keep an eye out for the rifle magazine thanks for the tip.
 

dave_person

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Hi,
Siler kits go together very easy. You can usually trust the witness marks and parts are well cast. That is not the case with many other parts sets. Also, Siler kits usually have instructions and a drilling guide for the tumbler hole in the bridle. It is very helpful t have a drill press.

dave
 

Ajgall

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Just an update it’s a lot of polishing and fitting, but is going well I’ve only had one major mishap the pan slipped in the drill press vise and ended up horribly misdrilled. After some self loathing and a few words I don’t use at church picnics I was able the plug it, weld it up and re-drill and tap with better success.
 

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