Making square holes for square pegs (cock installation)?

[Hemo]

Okay, I need a little advice here. I'm building a lock (Kibler Dolep) from cast parts, and I'm about at the point of installing the cock. There are some faint marks on the cock casting indicating the direction of the original square hole, but this is probably irrelevant since the tumbler is totally cylindrical. What's the best method for filing square holes in the cock and a square post on the tumbler shaft, to get the cock to appropriate position (flat inside cock stop against the lock plate with the spring almost relaxed)? File the square in the cock first, or on the tumbler shaft? I have plenty of extra length on the tumbler shaft, could start filing a taper out there to get started, modify the angle at the cock works down to the plate?

Thanks for any help!

Gregg

[Scota4570]

Do the tumbler first.  Put a puddle of soft solder on the cock.  Use the screw to draw the cock against the tumbler in the desired position, tap it a bit the be sure the mark is strong.  Use the mark in the solder as a filing guide. 

[SingleMalt]

I'd file the tumbler shaft square first and make sure it's got a slight taper toward the end of the square portion.  Measure it side to side and pick the nearest drill bit that's smaller.  (This is where wire gauges and numbered bits are handy.)  Drill the cock with the selected bit.  With the bridle and tumbler assembled to the lockplate, rotate the tumbler to its rest position.  Place the cock on the lockplate beside the tumbler in the rest position.  Ideally, the stop should be on the lockplate.  Mark where the corners of the tumbler flats should be.  I use a scribe and darken the side of the cock with a marker.  Use a small square needle file and start by filing a small groove at each mark.  Continue up to a larger file.  Check the fit often as it gets close.  It should take some force to seat the cock onto the tumbler.  It shouldn't just fall into place.

[James Wilson Everett]

Check out the topic, "making a gunlock".  This shows photos of the method suggested by the two responses above.

Jim

http://americanlongrifles.org/forum/index.php?topic=26825.msg255966#msg255966

[Hemo]

Thanks for your responses. That's enough to get me going. Jim, I read your great tutorial on "making a gunlock", but I had forgotten about it when it came time for this task.

I've been meticulously taking progress pics of the building of this lock, and I'll post them when it's done.

Gregg

[Bob Roller]

Do the tumbler first.  Put a puddle of soft solder on the cock.  Use the screw to draw the cock against the tumbler in the desired position, tap it a bit the be sure the mark is strong.  Use the mark in the solder as a filing guide. 

Use the smallest screw that is practical to hold the cock. I see locks with small shank tumblers using an 8x32 and
I wouldn't consider that size.I have used a 6x40 for decades and on rare jobs, a 5x40. On one tiny lock for a Fenton
pistol I used a 4x40.

Bob Roller

[Hemo]

The screw set made for this lock by Tom Snyder uses a 6x40. I just finished drilling and tapping the end hole in the tumbler and filed the tumbler shaft square. Looking OK so far!

Gregg

[jerrywh]

 I broach all my hammer holes with square broaches. When building a lock from scratch I install the hammer on the tumbler blank before I shape the inside of the tumbler for the spring or sear notches.
as fro screw sizes I do the same thing as Bob Roller. 4-40   6-40 5-40 Rarely ever use an # 8

[westbj2]

Like Jerry, I prefer to mount the hammer to the tumbler shank before shaping the interior blank.  Pictured below  is a variation of using a broach to fit the hammer hole. 
First, rough file a square hole that will just start on the small end of the tapered stud.  With a hollow punch, drive the hammer down on the tapered stud until it bottoms out.  Then turn the nut to force the hammer up and off the stud.
The result will be a perfect tapered square hole which still needs to be fitted to the tumbler shank.  Careful filing here will result in a great fit.
Jim

[jerrywh]

 I really like the idea westbj2 has.  It is a lot simpler than making a regular broach.  Here is a photo of some of the broaches I have made.  I have about 3 or 4 more. One of these is about 55 years old.



That cherry that is in the photo was made for the first flintlock I ever made from scratch. It had a Bill Large barrel that was 441 caliber.  There was no round ball mold available back then so I made the cherry and cut a mold.  

[David Rase]

That is a great looking tool westbj2.  I really like the nut idea to remove the cock from the broach.  I see some other applications for the same removal technique.
David

[JBJ]

westbj2,
Is the square tapered stud hardened in any way. Excellent idea!
J.B.

[westbj2]

Particulars on the hammer swedge.
Body is made of O-1 tool steel, hardened and drawn back.  The nut is from a hold down clamp set as used on a milling machine, it is also hadened.
If I were to make another it would have "shoulders" to prevent down movememt in the vise and keep it square while forcing the hammer down.
The idea is not all mine, Lynton McKensie had something similar in his antique gun making tool collection.  It does work very well and produces a nice hole quickly.  A 2# hammer works best.
Jim