Broken Hammer Screw


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#2
It appears that there is enough of the screw shaft remaining that a small pair of vice grips could grab. I would put a drenched cottonball with a good rust loosening liquid -- I've always had best results with Kroil and I've used it a lot -- on the exposed screw shaft and let sit and penetrate overnight and you should be able to back out the broken shaft with the vice grips.

edit to add - If the broken screw shaft is not protruding from the hammer and is an optical illusion on my end, then it's probably best to take the sideplate assembly into a gunsmith and have it removed.
 
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Mar 12, 2018
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Mobile, AL
#3
It appears that there is enough of the screw shaft remaining that a small pair of vice grips could grab. I would put a drenched cottonball with a good rust loosening liquid -- I've always had best results with Kroil and I've used it a lot -- on the exposed screw shaft and let sit and penetrate overnight and you should be able to back out the broken shaft with the vice grips.

edit to add - If the broken screw shaft is not protruding from the hammer and is an optical illusion on my end, then it's probably best to take the sideplate assembly into a gunsmith and have it removed.
Thanks. No, it's not protruding - down a few millimeters unfortunately. Wasn't sure if I could drill it out safely. Bummer
 
#4
Thanks. No, it's not protruding - down a few millimeters unfortunately. Wasn't sure if I could drill it out safely. Bummer
Yes you could still soak it and drill it if you can prevent the bit from "walking" and then use an ez-out.

edit to add - To do that I'd recommend pulling the hammer off the tumbler and disassemble the plate so you secure the bolster in a vise on your drill press.
 
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Jun 13, 2016
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Bloomington, IL Corvette Gold
#5
Soak it with a good penetrating oil; I, too, use Kroil.
CAREFULLY locate the center of the screw and punch a center mark. Then use a LEFT HAND twist drill at slow speed until it gets a 'bite'; should be able to back it out.
If possible, use a drill press to apply pressure to ensure a good bite.
 

Jobe Holiday

Sergeant Major
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Mar 1, 2010
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The Perpetually Frozen North
#6
The hammer screw broke because it was hardened to the center of the screw, which made it brittle enough to shear off. Lock screws in general, including the hammer screw, are often hardened through the entire body of the screw, which is why they are often found broken off. Removing them can be a challenge, with the tumbler posing an even greater level of difficulty because it's shape makes it difficult to hold securely, and square, while carefully drilling it. My advice is to use nothing less than a drill press and cutting oil. Once you get a hole through the screw you will find an open space below the screw, as it does not bottom out completely. I would suggest that you stop at this point and add some additional penetrating oil and wait another day to two for it to work up from the bottom. At this point you may be able to gently work it out with an easy-out. If it is stubborn warm the square shank just a bit with a propane torch, but only to the point that you can still touch it with your bare fingers, this allows for a slight expansion of the walls of the square. Then try it again. Just my thoughts, with no guarentees on the end results! If all goes South, you have an interchangeable parts musket and original tumblers can still be found.
J.
 
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Sep 15, 2018
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South Texas
#7
I don't have a propane torch or a drill press. But I have been in that situation of removing stubborn screws. Expansion from heat is a good method, but I've found the opposite to be true (sometimes), Contraction from cold can also work . Place the lock in the freezer and work on it tomorrow. But do use the oil.
 

gary

Captain
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Feb 20, 2005
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5,954
#9
I'd disassemble the lock leaving the hammer, tumbler and lockplate together.
Then apply kroil overnight to loosen the screw.
Then drill and tap the screw. Don't go too deep (mark the drill and the tap) let you bore into the tumbler.
Insert a screw and tighten (thread should be reverse of the stuck object).
Unscrew using newly inserted screw.

BTW, I like what Jobe suggested too but would use a milling machine. By raising the table via the knee, you can precisely mill out the old screw to the thousandths.
 

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