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Old 04-25-2008, 02:54 PM   #1
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Default TB1 - Connecting Rods

Here's where we'll put the con rod log.

While I wait for reamers from Enco, I'm planning strategy. Currently I have two approaches and wonder what the collective "Wisdom of the Crowd" thinks would work better.

Approach #1: A little turning, a lot of milling, no new fixtures needed

The idea is to use collets on mill and lathe, and extend just as much as we're working on for maximum support. We'll start at the skinny piston end. The process goes like this:

1. Turn stock slightly oversized so it fits true in a collet.

2. Push it into the collet so we have just enough for the piston end. Turn to diameter.

3. Take to mill in the collet and stick it in the spin indexer. Mill one face flat, spin indexer to the other side, mill the other face, then drill and ream for the wrist pin.

4. Do the skinny long piece next. It's just a turning op. Probably need to use the tailstock to support it, although some of the "box tool" arrangements are intriguing.

5. Turn the fat crank end next.

6. Take to mill and spin index again.

I had considered building a tailstock for the spin indexer. But this plan always has the part being milled hard up against the collet so it is supported.

Approach #2: Almost all lathe, except the reaming. Requires a v-block fixture.

The idea is to make up a v-block that fits in a collet. I'm envisioning something similar, though not as elaborate, to Ed Dubosky's clever blocks if you have seen those.

1. Turn the 3 sections to diameter.

2. Insert the v-block (round cross section, not square, with a "v" across the face) in a collet. Clamp the con rod in the v. The block's diameter is such that it perfectly fits the skinny length so you're automatically centered properly by the overhanging larger diameters.

3. Use a facing operation to get the flats on the con rod.

4. Index the other side at the surface plate with a suitable gage block underneath the previously ground flat. Back to lathe to do the other side.

5. Use the same v-block fixture in a collet block over on the mill to drill and ream. I can use my vise stop to knock them all out one side at a time very quickly once I've lined up the first one.

I'm tending towards approach #2. Unfortunately, I don't have quite the right cutters to do the v-block "v" easily. I thought I had it with a small dovetail cutter and then I broke a tooth at the very end of the last pass before finishing. Doh!

Next up is to try a regular end mill and angle the block. It's awkward since the block is round, but I'll use my collet block and adjustable angle plate to set it up in the vise.

Any thoughts?



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