Measuring Percussion Hammers

[pilot]

My old W. Richards shotgun has a broken hammer spur and I'm trying to source a replacement.  Track has hammers pretty reasonable, but I'm confused on how to measure what I need.  They are listed based on "hammer throw".  I surmise that is the travel of the hammer from full cock to contact with the nipple.  Is this correct? 

How do I go about measuring the hammer to get the right replacement?

[rich pierce]

From center of hammer axle to the surface that strikes the nipple.

[D. Taylor Sapergia]

Yes, on a percussion hammer, measure from the centre of the square hole to the centre of the hammer cup.  On the shotgun, measure from the centre of the tumbler hole in the square stud sticking out of the lock plate, to the centre of the nipple.
On a flintlock, the cock throw is the centre of the tumbler axle hole to the tip of the bottom jaw.
You may want to buy a pair of matching hammers as replacement hammers, as replacing only one of them will always look a little weird.

[pilot]

The center of the axle to the center of the nipple is the throw?  I misunderstood the search results I found here, then.  I'm not surprised at that.      I didn't know if the angle of the axle shaft to the "head" of the hammer was important or not.

Thank you, gentlemen, that fixes my problem.  My hammer measures 1 11/16 and Track has one that measures 1.745.  Close enough.   

[D. Taylor Sapergia]

Measuring centre to centre will get you into the ball park.  All hammers are built with offset, but many still required a bit of tweeking to get lined up correctly.  But you start with one that is as close as possible to the right throw.
For a wrench to adjust a hammer, I made mine out of a strip of 1/4" thick mild steel bar.  I drilled a hole in one end, and then filed it so it would slip over the nose of the hammer.  I also rounded the corners of the hole everywhere so it didn't gaul the hammer when I applied the pressure to bend it.  Most hammers can be bent cold, but I've heated some red on occasion too.

[Scota4570]

If you buy a cast hammer be sure the tumbler square is oriented correctly.  IF not be prepared to change the square. 

[D. Taylor Sapergia]

Scota4570 makes a very astute observation.  Hopefully, your replacement hammer will not have a square hole cast or cut into it.  If it does and it is not right, you can drill out the square hole to round, install a plug made from a piece of mild steel rod, silver solver it in place, and then drill and file a new square hole.

[pilot]

I got the hammer today and it has a square hole that is cut wrong.  Can I just weld it closed and redrill it and cut it to the angle I need?

[Gaeckle]

Yes

[D. Taylor Sapergia]

I have filled many hammer holes to re-cut for a better fit.  I file out the hole with a rat tailed file until I am almost to the corners of the square, and then use a drill in the drill press to finish the hole.  Then I turn a piece of mild steel for a friction fit in the hole, and silver solder it in place.  I dress off both sides of the hammer, centre punch the centre and drill a new hole that is just short of the tumbler square's width.  Cutting the square with safe sided needle files finishes up the new hole so that it is a tight fit over the tumbler square.  The hammer screw head covers the silver solder line.  But welding it closed would be a great way to go too.

[Daryl]

When Taylor is talking about silver soldering, he is likely talking about hard (high temp) silver soldering.