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Tom Griffin
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Tonight's task was to cut the relief in the stock for the mainspring assembly and get it mounted. That involved making something I've never made before, wood screws. Their purpose is to attach the stock to the receiver through the upper and lower tangs. They are 3/16" diameter (#10) and about an inch long, with oval heads and the typical tapered sharp V thread used on wood screws.
The shank of the screw was turned to .188 and the taper attachment used to turn a 10º included angle taper.
The threading tool is 30º instead of the normal 60º and has a .058 flat on the point. I broke two of them off before getting wise and using a center in a super small center hole. I withdrew the tool at the end of the thread for a cleaner look, easy to do on the Hardinge with its quick acting lever on the compound. The same can be done on any lathe by stopping the spindle at the end of the thread and rotating it by hand as the tool is backed out with the compound crank.
Cutting a 90º angle under the head of the screw to match the countersunk holes in the receiver.
Parting off the partially finished screw.
The diameter of the head finish turned and parted to length, leaving stock for the oval shape on the head.
Machining the oval head on the screws with a form tool.
Cutting the screw slots using a collet block in the mill with a .045" slitting saw.
The finished wood screws.
Cutting the relief pocket for the mainspring assembly on the mill.
The firing pins is simply a 3/16" diameter piece of drill rod, turned down on one end, flatted for a retaining pin and tapered to the traditional wedge shape used on rimfire cartridges.
After turning down one end, it was mounted in a collet block on the mill, centered with an edge finder and the flat to index and retain the pin was cut with a 1/8" 4-flute end mill.
Then the block was turned on end and the wedge shape cut with a 45º end mill. I had to break out the old eye loupe to measure the .020" flat with a rule. The opposite end gets a radius to match the rear contour of the breech block. Rather than go to all the trouble of setting it up on the rotary table, I'm going to take the easy way out and just mount it in the breech block using the block as a pattern to cut the radius with the belt sander.
Here's the finished firing pin installed in the breech block. Another member pointed out that the newer model Favorites have a modified firing pin to prevent possibility of gases from escaping around it (inches form your eye), so I'll probably do a re-design on this one. I'm thinking to keep it looking original, I'll add an internal O-Ring to the pin to serve as a gas stop.
No pictures this time because the part has already been made once. Last night I re-made the link that connects the lever to the breech block. The link does double duty by also moving the hammer to the half cock position and I wasn't happy with the way it worked. A redesign moved the part of the link that pushes on the hammer farther away form the hammer pivot point. Now it does what it's supposed to to do without binding. That's the thing about prototype parts; sometimes they need to be tweaked and remade but it's all part of the process. Once the action is working to my liking I'll probably harden it to prevent damage to the sear and notches from playing with it too much.
The shank of the screw was turned to .188 and the taper attachment used to turn a 10º included angle taper.
The threading tool is 30º instead of the normal 60º and has a .058 flat on the point. I broke two of them off before getting wise and using a center in a super small center hole. I withdrew the tool at the end of the thread for a cleaner look, easy to do on the Hardinge with its quick acting lever on the compound. The same can be done on any lathe by stopping the spindle at the end of the thread and rotating it by hand as the tool is backed out with the compound crank.
Cutting a 90º angle under the head of the screw to match the countersunk holes in the receiver.
Parting off the partially finished screw.
The diameter of the head finish turned and parted to length, leaving stock for the oval shape on the head.
Machining the oval head on the screws with a form tool.
Cutting the screw slots using a collet block in the mill with a .045" slitting saw.
The finished wood screws.
Cutting the relief pocket for the mainspring assembly on the mill.
The firing pins is simply a 3/16" diameter piece of drill rod, turned down on one end, flatted for a retaining pin and tapered to the traditional wedge shape used on rimfire cartridges.
After turning down one end, it was mounted in a collet block on the mill, centered with an edge finder and the flat to index and retain the pin was cut with a 1/8" 4-flute end mill.
Then the block was turned on end and the wedge shape cut with a 45º end mill. I had to break out the old eye loupe to measure the .020" flat with a rule. The opposite end gets a radius to match the rear contour of the breech block. Rather than go to all the trouble of setting it up on the rotary table, I'm going to take the easy way out and just mount it in the breech block using the block as a pattern to cut the radius with the belt sander.
Here's the finished firing pin installed in the breech block. Another member pointed out that the newer model Favorites have a modified firing pin to prevent possibility of gases from escaping around it (inches form your eye), so I'll probably do a re-design on this one. I'm thinking to keep it looking original, I'll add an internal O-Ring to the pin to serve as a gas stop.
No pictures this time because the part has already been made once. Last night I re-made the link that connects the lever to the breech block. The link does double duty by also moving the hammer to the half cock position and I wasn't happy with the way it worked. A redesign moved the part of the link that pushes on the hammer farther away form the hammer pivot point. Now it does what it's supposed to to do without binding. That's the thing about prototype parts; sometimes they need to be tweaked and remade but it's all part of the process. Once the action is working to my liking I'll probably harden it to prevent damage to the sear and notches from playing with it too much.
