New hammer hole

[smylee grouch]

Over the years I have welded up a few hammer holes and retrofit a few hammers but it seems that I most always got the hammer hole off just a little making for a lose fit. Are there any tips to do this job more neatly?

[chubby]

Hi Smylee, I will mic my tumbler square and drill the new hole a 1/32 smaller and use a small square file and file corners a little at a time after blueing.     Chubby

[jerrywh]

 Besides all the other precautions of making a nice square hole I have found that the best way to get a good tight fit is to make sure the hole is slightly tapered.  With a tapered hole and preferably the hammer should have a slight taper also.

[smylee grouch]

What is the best way to locate the "square" in the hole?

[L. Akers]

I use the tumbler to locate and orient the hole in the hammer.  I drill a precice BODY sized hole in the hammer based on the screw size and located at the pivot point of the hammer.  Coat the inside surface of the hammer with layout dye.  Put the tumbler at full cock and attach the hammer to the surface of the tumbler with the screw at the rotation desired.  Mark around the tumbler square onto the hammer with the tip of an X-acto blade.  Now you have the hammer correctly marked and ready to remove the materiel in the square by drilling and filing.  The insides of your marks are the outside of the tumbler so make sure you leave the lines.  As you approach the lines, begin trying to fit the hammer onto the tumbler.  File little, fit often.

[Mark Elliott]

Great tip.

[smylee grouch]

OK L , Thanks for the tip. In the past I would drill a hole slightly smaller than the dia. of the tumbler shaft, lay it over the tumbler and try to mark the square points then file them out. A good fit was seldom achieved but it was serviceable. Your system sounds more consistent and sure fire. There are probably several other ways to accomplish this task that are better than the methods I used.

[D. Taylor Sapergia]

    Determining where the corners of the square hole must be, is not a simple task.  Ideally, the cock should strike the edge of the plate at the end of its throw at the same time that the tumbler comes into contact with the back edge of the bridle.  This stains the lock overall the least when the cock comes to rest.  At the same time, the mainspring should stop very close to the tip of the tumbler ramp without dropping below the edge of the lockplate. 
    On a blank cock, I polish the back and tin it with soft solder.  Then with the lock in the fired position, I lay the new hammer over the tumbler square so that the hammer stop on the inside back is just slightly below the edge of the lockplate, and give the face of the cock a solid tap with a hammer.  The tumbler square is now marked in the solder on the inside of the cock.  Drill the hole undersized, and file the tapered hole to fit.  Then when filing the contacts, hopefully to fulfill the first paragraph above, you will have a little metal to work with so that everything comes out well.

[jerrywh]

 If I'm making a new lock I put the hammer on before I finish the  tumbler. I put it on when the tumbler blank is in the round or close to it.
   It it is a replacement hammer I just glue the lower half of the old hammer on the back of the new one, drill the hole and broach out the square.
   Otherwise my process is something like Taylor's. You can put anything on the back that will take an imprint. I don't file out my hammer holes any more. I broach mine now but they always need some fine fitting because a broach doesn't make a taper. The taper has to be done by hand.

[smylee grouch]

Another two good tips. I had thought about the hammer stop on the lock plate but had forgotten about the tumbler/bridle one, both important considerations, thanks Taylor and Jerry.