[quote]N8 If your bar is 3/4" thick, I wouldn't worry too much about losing thickness by flycutting both sides. I don't think you would need to lose much more than 0.01 - 0.03" getting your bar flat on each side unless it was really warped.[quote]
I don't know... It looks pretty badly warped. I've got two hunks cut off that are going to be the blocks. If I put them together so the concave sides are facing, on the edges it looks like about a 1/16" gap in the middle. If I put the convex faces are together it is a big rock. The other test I did is that I have one of those pocket steel rules with a sliding pocket clip on it with ears like a depth gauge. If I pull the clip off, and use the ruler to bridge the high spots, the ear on the clip goes under it easily in the center. ;(
I'm guessing I'll have to get rid of at least .05" on each side. Still not a huge amount, but...
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That is not much in comparison to the 3/ 4" thickness. I would just flycut a smaller piece that you have already cut off instead of the whole length to see how much is really necessary to take off.
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That's what I was planning - I figure don't mess with the big hunk till I know what I'm going to do with it.
I wouldn't want to mess with the big chunk until I chop it up anyhow since it's currently longer than either axis on my Smithy.
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If you don't want to deal with flycutting, take one of the cut pieces and sand it with 220 grit SiC sandpaper and water or even a stationary belt sander (if you have one) to get it pretty flat before machining. You want to true it up before machining any O-ring grooves or channels into it. Flycutting would be fastest and best, but this also depends on your equipment and experience.
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Well, I figure I won't learn flycutting or other machining skills unless I actually do them, so I've got to get on it. I have a hand held belt sander, but I don't know how true it is, nor do I think it would be happy to have me sanding copper and potentially getting little copper bits in its innards :shrug:
My skills are beginner level, and my equipment isn't very good by todays standards, but I think it's adequate for the task. When I was facing off my cut ends, I had lots of problems with my setup initially, but once I got everything debugged, the ends looked pretty good. Of course I was wanting to have the blocks be 80mm long, cut them (with a Sawz-All) to about 81-82mm, and ended up at 78mm, but that's a different story....
I think my planned design is also going to be fairly tolerant of most everything except the lapping. I'll be soldering the block together so I don't need to worry about O-rings, and the top / bottom fit only needs to be fairly close. I'm going to be cutting my water channels as close to the bottom as I can get away with (my target is 3-4mm base thickness) but that gives me enough room that if I'm off a bit it won't hurt anything.
All in all, I think I have something that will do a good job, but be pretty tolerant about how perfect I get everything in building it.
Gooserider