Part 10 of the build log, the valves/guides/springs, final continuation:
Since I redesigned the valves to use c-clips, I had to make the c-clips. The first bit was easy enough - machine the OD, drill a 2mm (0.079") hole, and part off to the desired thickness:
That, of course, gave me an "O" rather than a "C"; the hard part was how to cut out the opening. I set a piece of scrap in the vise on the mill and milled a slot just wide enough to hold the O's that I had parted off:
I used medium strength (blue) loctite to secure the blanks in the slot; in retrospect, I should have used superglue or red loctite. However, this time I had made an extra blank just in case:
I used a 2mm endmill, taking very light cuts, to cut out the openings:
Good thing I made the extra blank - as I noted above, the blue loctite was not quite adequate, and one of the 3 blanks shifted loose, preventing me from completing the machining on it. Fortunately, the others stayed in place, allowing me to complete the 2 c-clips I needed:
The last bit in this part of the build was to make the valve springs. This was the first time I have attempted to make springs, and I have to say that I was pleased by how it went.
Before making springs, I had to make two accessories. First I made a "gripper" - not a very elegant piece, and I don't have any pictures or design to show - just a couple of pieces of scrap steel with a small slot between, such that I could clamp down using the tool holder screws to get the desired grip on the wire. Second, I made an arbor of the appropriate size - or at least, what I hoped was the appropriate size; I had trouble finding a table in Machinery's Handbook that quite gave me what I needed, so I had to extrapolate. (It seemed to work.) I drilled a .040" cross hole though it as a way to hold the start of the music wire.
Finally I could make the springs. I calculated and set the thread pitch that would give me the desired number of turns over the length called for in the plans, put the wire through the gripper and through the hole in the arbor, and adjusted the grip tension:
On the slowest speed of my lathe (30 rpm), I let it build a few starter turns, then engaged the half nuts to create the body of the spring, then disengaged and let it make a couple of finishing turns:
After snipping the wire, it sprang open a bit, just as the book said it would:
I trimmed down the start and finish turns, and tried it out - and it worked beautifully. My first spring (and the second that followed it) were a success!
This concludes part 10 of the build log. Next up will be a relatively simple part, the rocker arm.