Milling the mainspringThe main spring is made from a rectangular blank of 1075 that’s 125mm x 17mm x 5,7mm and the paper pattern glued on.
The first step is to mill out the peg that’s 2.5mmx2.5mm x7mm located on the upper arm of the spring. The peg is place as close as possible to what will become the inside of the spring. Will explain why later in the process. I apologize for the poor quality of the pictures. The peg is then rounded with a 2mm hollow mill.
The tab for the upper arm is milled out next and the profile of the spring afterwards. You can see the profile on the top of the paper pattern in this picture.
The blank is then soft soldered to a piece of square stock and the thickness milled down to 3mm. The ends are left full thickness.
Next, I made two tapered pieces of square stock. One for each limb of the spring. These were soft soldered to the spring blanks and the taper of the arms milled down. NB! The taper is milled on the inside flat of the spring.
Draw file and polish the inside of the spring before removing the last tapered block.
Mount the block on the lower limb in the mill and drill out a 2.5mm hole at the outer edge for the hook. File out the slot and finish shaping the hook on the outside.
Bending the spring.Make a bending jig out of square stock. Notice the cutouts for the peg and the tab. The jig ensures that the bend always comes in the same place. Clamp the blank in place, heat with a torch, hammer to 90 degrees.
Close the bend, heat the tab and bend it upwards. Place the spring on the lock and mark where to drill the peg hole.
File the top of the tab so it fits against the lock bolster. Heat lower limb and curve it so the hook extends about 6mm below the lock plate to preload the spring.
The main spring is heated to bright orange with an oxy/acetylene torch and quenched in motor oil. Tempering is done in a heat-treating oven at 371 Celsius for 20 minutes.
The link between the tumbler and mainspring.The link is made of a piece of 1075 steel 7mm x 8mm x 26mm. Soft solder the blank to a piece of square stock and mill out a 3mm x 3mm peg at one end that’s 3mm high. Round peg with a 2.5mm hollow mill.
Remove from square stock, resolder to square stock with the round peg pointing down. Mill out a 3.5mm x 3.5mm square peg place opposite to the round peg. Mill the tang of the link down to 1.7mm-1.8mm. Sorry forgot to take pictures.
Next make a jig that will insure correct placement of the pegs in relation to each other. Take a piece of flat stock, drill and tread two screws for a metal strap to hold the blank. Drill a 2.5mm hole and lock the table. Mount the blank in the jig with the round peg in the 2.5mm hole. Round the square peg with the 2.5mm hollow mill.
The link is going to be attached to the tumbler arm with a short 2.5mm silver steel axel. The next step is to find the correct distance between the link pegs and the hole in the tumbler arm. Mount the tumbler on the lock plate in the fired position. Place the spring on the lock plate with the hook barely inside the plate. Measure the distance between the inner edge of the hook and the edge of the tumbler hole. Repeat with the lock in the cocked position.
Ideally the length should be the same in both positions. Adjustments can be made by either reducing the height of the main spring tab or increasing the curve on the lower mainspring arm.
Paint the tang with dykem, strike a line down the middle, mark the distance between the pegs and the holes. Add 1.25mm. This is the center for the hole in the link. Drill hole.
File down the tang around the pegs so the link can move freely in the main spring hook. I used a sjarn jig to hold the link while filing.
Mount the link blank in the tumbler arm and remove unneeded metal. The finish link is hardened and tempered the same way as the main spring.
Status so far.I now have six functional locks and have cleaned up four of them. Takes about a day to get rid of most of the scratches, dings and machine marks on a lock. The lock sanded to 400 grit and tumbled for 6 hours with soap and steel shot. This gets rid of the sanding marks. Finished four locks, two more to go.
The last step will be case hardening the tumbler, bridle, sear and screw heads. It’s snowing here in Norway, so I don’t know when I’ll be able to do that outside.
Best regards
Rolf
Links to the other parts:
left-handed Alex Henry/Staton/Bob Roller lock. Part 1. Lock plate and Hammer
https://americanlongrifles.org/forum/index.php?topic=73225.0left-handed Alex Henry/Staton/Bob Roller lock.Part2. Four post bridle and screws
https://americanlongrifles.org/forum/index.php?topic=73497.0left-handed Alex Henry/Staton/Bob Roller lock. Part3 The tumbler.
https://americanlongrifles.org/forum/index.php?topic=73935.msg736278#msg736278left-handed Alex Henry/Stanton/Bob Roller lock. Part4. The sear and searspring.
https://americanlongrifles.org/forum/index.php?topic=75495.msg750459#msg750459left-handed Alex Henry/Stanton/Bob Roller lock. Part5. The fly.
https://americanlongrifles.org/forum/index.php?topic=77291.msg765744#msg765744
