Now that I’ve got the measurements for the eccentric rods, it’s time to make them. It turns out that one needs to be about 8 thou longer than the other. But they are both about 25 thou longer than Kozo showed on the plans. I guess that’s why he says to measure them and make them THAT size!
The eccentric rods were made from 1/8” x 1/4” 1018 flat bar.
The first op was to drill the center for the end holes at exactly my measured values. I made the holes an interim size so it's easier to hold in a jig. I’ll drill them out to the final size when the rest of the machining is done.
With that done, I will do the rest of the operations relative to the holes themselves. That way I don’t have to worry about the actual lengths of the rods. So here I’m using a gauge pin to center on one of the holes before the next op.
Which is to drill 1/8” holes that help define the rod from the rounded ends. This is the small end, so it only gets 2 holes. Since some of these holes are on the edge of the part I used a 1/8” center cutting end mill for this op.
Now, this is the big end. It has an oil fixture built-in. So I drilled four holes; above and below the rod, and then to the left and right of the oil fixture. Again, all holes locations were measured relative to the center of the big-end rod hole.
And then I drilled the oil hole.
Now we start to shape the rod. I used a roughing mill to take down the bigger side some. This is not the final tapered shape, but it gets rid of a bunch of metal before the next step. Just to help give context I put the part I hadn’t done yet in front of the vise jaws so you can hopefully see the difference between the two. I also took a little metal off the small end and took the oil fixture to the correct height.
Next, I filed the ends round using filing buttons.
Now to thin the rod section down I mounted it vertically to the jig and peeled off a bit from each side. This is why I used the roughing mill to take out a bunch of metal. It just made less to thin here. The picture shows just after completing the first side:
With the sides thinned, it is now time to taper the rod. While this looks like the same jig (and it IS the same hunk of aluminum) I actually drilled a different set of holes that holds the rod at a very slight angle (about 0.46
o or so). Then a few careful passes on each side here and the rod was all tapered.
With that, the rods are complete! Except, now that I look at the picture I realize I never re-drilled the holes to the final size. So I’ll be doing that first thing next time! But that shouldn’t take much effort.
I still have a bushing to make for the big end, then it’ll be ready for assembly.
Thanks for checking in on my build!
Kim
