Building The Steven's Favorite

[TomG]

Not much time for the project tonight. Between a couple of chores and tip-off time time, I was only able to make the screw that attaches the end of the mainspring plunger to the receiver. Just a simple 8-32 thread, a .04" wide parted groove and a screwdriver slot in the head. This is the perfect application for a collet block.





The next task will be to make and install the pin for the clevis and to wind the mainspring if I have the right size music wire on hand.

Tonight I got started on the mainspring plunger. The Steven's uses a compression coil spring for a mainspring and it sits on a rod with a clevis on one end with a pin in it that pushes against the hammer. The other end rides in a bushing that hooks on the grooved screw that I made last night.



The first step was to square up a piece of O1, rough out the turned end and center drill each end so it could be turned between centers.



I rarely turn between centers so I didn't have the proper size dog on hand. The alternative was to drill an oversized center in the yoke end and use that to drive it. Thye driving center is just a piece of aluminum turned to a 60º point. It should work fine because the shaft is only 5/32" diameter and won't require much torque to drive.





The radii were cut with a corner rounding end mill. Next, the center of the clevis gets milled out. Not tonight though, it's been a long day. I'll be working at home in the morning and will need the mill so I guess I'll just have to finish it then.



Toolmaker's clamps aren't used often, but they worked well here to stabilize the .075" thick fingers on the clevis. Even so, with the long thin fingers and the long end mill, the potential for a spectacular wreck was high.







It's a nice day outside but I still managed to sneak into the shop for a bit and wind the mainspring. The method I use to make springs is to set the lathe up for the number of coils per inch, put a slotted wooden insert in the tool block to pinch the wire and provide tension and wrap it around a mandrel under power. The spring always ends up larger than the mandrel so figuring out the right size mandrel requires some experimentation. Once wound, it was clipped to length and the ends ground square on the belt sander.



This is the wooden tensioning block sawed out of a leftover piece of walnut from the stock. The amount of tension required depends on the diameter of the wire and sometimes takes some trial and error to get right.



Safety glasses are a must when working with any kind of wire, especially when winding springs. The mandrel I ended up using was a long aircraft drill about .015" under the finish diameter of the spring. Forcing springy wire to conform to the shape you want is a dicey proposition, so it's best to run the lathe at slow speed and stay well clear of the wire. The end of the mandrel is supported with a drill chuck snugged up and well oiled. The start of the spring has a 90º leg bent on it and pinched in the lathe chuck along with the mandrel.



The finished spring mounted on the mainspring plunger.



The spring force on the hammers feels a tad light, but it is only a .22. If it misfires I'll just re-wind the spring with .055" or .063" wire instead of the .047" I grabbed at the hobby shop. The hammer doesn't fall all the way yet because I still need to cut the notches and the extra stock is hitting something inside the receiver.