Re: Making a smoother according to the Work Magazine Reprint Project
05/31/12 11:03 PM
Alrighty, now. Here's some info on the lever cap and screw pattern(s)...
As I've hinted at and we've discussed earlier, I plan to cast some cap screw blanks oversize so they can be turned and threaded to suit with little material waste. I plan to cast some trials of these this weekend with the lever cap castings.
The screw pattern depends on the parting line passing through the center axis. The major diameter of the pattern is just shy of one inch: I've chosen a 1-1/8" diameter maple dowel, sawed, and planed the parting line to split the dowel. Next, the dowel is glued back together with a slip of paper in the joint to allow separation again after turning. The dowel is now not round in diameter, but that will turn out soon enough.
And split apart after the final turning passes.
Notice the shoulders of the turning: nothing is square or undercut. Tapered shoulders are for draft to ensure clean release from the mold. This part is purposely oversize to account for shrink and adequate cleanup, and of rough form to allow for all the final turning details in metal.
The end elements of the turning are for channels in the mold. The end of this half is trimmed with the appropriate sweep in-cannel gouge at an undercut bevel...
...to match a pouring boss. This boss is where the sprue is cut into the sand of the mold for pouring. It's a little hard to see here, but notice the grain direction in the turning. It's running vertically to minimize potential splitting in use.
The two halves back together to illustrate the parting line. Please excuse the blood blister!
I will post more photos of the screw pattern as it is mounted on the matchboard. Sorry if the methodology is not all clear yet--it will be soon. Now, it's time for the lever cap!
Joel sent me some photos of Norris lever caps and suggested I make a hollow in the underside, rather than just have a solid lever. For some reason I really like that idea. Here, I'm roughing-in a radius relief after carving out the "shield" hollow.
Again, I cannot say enough how nice this wood is to carve. Buttery.
More in-cannel gouge action: cleaning up the relief "swoop".
Set into the matchboard. I struggled with my process here because I wanted to avoid all detail carving and such in stinky plywood. The problem is now allowing for the radius on the top side of the lever cap. I had to adjust things here slightly because my cap pattern is too thin for this procedure.
The cap pattern only protrudes about 1/8" from the top side of the board (instead of the 1/2" I need). So I made a "scab" to give it the depth I need, plus the radius of the top of the lever cap.
See? I love glue. Don't fret about the overhangs, I'll get to those soon enough.
That's all for today, folks.
The newly-improved casting, complete with cute little buttresses at the toe (worked great!). These will be removed along with the gating bumps before I ship the goods.