First, on a recommendation from Irish, I milled a short, wide "trough" along the length of the soft jaws. A little experimentation with 3D CAD showed me that a wide, shallow cut was a good approach. The cut is centered around 1" above the floor of the vise, and if everything works as intended, gives me three lines of contact instead of just one. The cut width was set by moving the cylinder into the jaw until it started to get too close to the counterbored screw holes (dashed lines, lower right) and then measuring how long the line segment is. Then I redid the drawing using a standard sized end mill and remeasured the depth.
This is a single pass, just about 1/32" deep with a 1/2" diameter end mill; an easy cut. Here's a view from the end without the pedestal where it's easiest to see, showing how the cylinder gets contacted in three places and not just one in the center. (Yes the camera's rotated; I'm not trying to look like an annoying commercial, it's hard to get the camera where it can see this). The vise jaw is the wall with horizontal lines that look like stacked bricks, made by the end mill that cut back the jaw, while the big round thing is part of the end of the cylinder.
After I added some thin cardboard for extra contact roughness, I put it in the vise, ensured it was level to a dial indicator, and tightened it up.
I'll probably try to cut it in the next day or so. Once I'm sure I've done everything reasonable to not barf it up again.
Why the decision to clamp it this way, instead of the suggestion to clamp it along the bore axis? Just curious.
ReplyDeleteTwo reasons. First, this is the way it's pictured in the book, so I know it can work this way. I've talked with people who have made these and no one said not to follow the book.
DeleteSecond, it has to be machined on that big flat end with a slitting saw that runs parallel to the table, so it has to be held this way at some point. If I can get by with one setup instead of two, I prefer that.
That said, the only time there are too many clamps is if you can't get to the work.
Good morning SiG.
ReplyDeleteI think you will be fine with that set up. Some extra foot lbs on the handle will make a world of difference.
One last idea would be to leave a "kiss" cut on the z-depth passes. If you want
to be extra cautious. Mill the Z in the 2 steps but leave .010-
.015 on the floor. At this point just loosen the vise slowly. Not all the way.
Keep a finger on the left side of the part as you "crack" the vise open ( maintain some force on the part not totally loosen). If, for some reason,
it has lifted you will be able to feel it settle with your left index finger.
At this point you can lightly reset the part with a tap from a soft deadblow hammer. There will be no tool pressure as you " dust " off the last .010-.015 in the Z.
I realize this is probably overkill but good practice skills for other projects as you gain confidence.
I think you will be surprised how tight you can get the vise without damaging the part.
Good luck :)
Irish
I hesitate to suggest breaking down your setup, but did you consider clamping the bad cylinder for a test run of the setup?
ReplyDeleteA wise man said, "You can't break it more than broken."
I'm not sure what the corresponding test would be. It couldn't lie on the flat side on the anything because that's a drastically different geometry. The flat spot can't touch either vise jaw because the clamping force isn't along a line or three, it's over a large flat.
DeleteNot to mention being crooked in any orientation.
I'd need a few hours to think about this.