Saturday, June 23, 2007

Fun With Band Saws; Happy Customers

I just finished making a set of casters for the Vixen HAL-110 tripod--by far the most challenging machining operation yet. This slides inside the tripod leg assembly, replacing the "foot" that ordinarily sits on the ground.

What makes it difficult is that I wanted something that would slide into a fairly complex hole (far more complex than the insert's end, and far more complex than really needed for Vixen's purposes) without being loose. And that's what I achieved--precisely enough machined that it doesn't fall out, but also doesn't have to be pressed in hard. Of course, I use the M4-0.7 screws that hold the foot in place to hold this insert in position as well.

It doesn't look like it should be all that hard to make, but with the amount of time it took, I think I may charge a pretty premium price to make any more. Even using the band saw to hack the big chunks out, while it saved a lot of time, still doesn't make these fast to make. The problem is that even with a 1.5" long cutting surface on this end mill, the power limitations of the Sherline means that you are removing at most .020" of Delrin at a time. If you try to remove more, you get some nasty vibrations and accuracy suffers.

Do you notice the "waffle" pattern? This particular end mill was a roughing mill--meaning that it concentrates on speed, not finish quality. If you hold the final result in exactly the right position, it kinda looks like a Manhattan skyscraper.

The Sears 10 inch band saw has turned out to be the best $170 I've spent in a long time. It is reasonably consistent. I set the fence at 1 1/8", and the piece that came out was 1.03" wide, so about .09" short. I set the fence at 2 1/8", and it cut a piece 2.04" wide, so about .08" short. I tried moving the scale on the edge of the table to correct for this, but there's only a very small amount of adjustment potential. I'll just remember that the cut is going to be a little under 1/8" narrower than the fence position, and that's good enough.

The other thing about it that is nice is that I can see where the blade is while cutting. The chop saw that I have, as powerful and quick as it is, is just too dangerous to use for cutting anything small.

The blade that came with the band saw works well for Delrin and for 6061 aluminum. I tried to trim a small piece of steel, and it was clearly not going to do anything but dull the blade. This is a woodworking blade, however, so I am not surprised.

One aspect of the band saw that has me a little confused is that it produces a bit of a wavy cut in Delrin. It doesn't seem to do this in wood or aluminum--very odd. It isn't a problem, since the only band saw work I do in Delrin is just a first step towards machining, but I suspect that there's something that I don't know that might produce a smoother finish.

I made a caster set for the Celestron 93493 tripod (first time for this model). The customer is singing my praises in this thread. Now, if all the other users of that tripod would just go ahead and order.

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