Artemia Salina wrote:

On Wed, 01 Sep 2004 22:49:37 -0700, Dave wrote:


I've been pondering the issues of clamping and holding work on a mill
table and I'm really not encouraged. The difficulty in securely
holding the material and yet leaving an empty space around it where
you plan to be cutting it, while still maintaining precise alignment,
seems like a really big headache for any small, thin, or irregularly
shaped (or curved) items. I think I'd need to have a $300 stack of
chopped up parallels and a half-dozen customized sets of vise-jaws to
even begin. Either that or resign myself to adding several unnecessary
threaded holes in each part -- just to hold them down. Am I
exaggerating the difficulty level?


I didn't need much more than a good sturdy milling vise to get me
started. You can make lots of clamps, jigs, and other work-holding
fixtures in a good vise. Parallels are a vital tool to have when
working with a milling vise, but since I have a bunch of square HSS
toolbits of different sizes I haven't needed to go and buy parallels
yet. I just stack some up under the work and I'm good to go. I just
made a pair of V blocks for a project I'm working on (a plate bender).
Since they're only made of mild steel I can't harden them, and even if
I could I can't finish grind them, but oh well, they'll suffice for
this project (milling a 3" long flat half way through a 2" diam.
carbon steel bar) and maybe a few others.

Probably the most challenging thing about using a miller is figuring
out how to set jobs up. As you find a need for a special item you can
buy it and add it to your collection, much like people do with drill
bits - purchasing only the ones they use often and not wasting money
on whole sets where half of the bits never see a chuck.


You're certainly correct. Workholding is half the challenge. Its deeper
even than this; design of good fixtures was what they did before CNC
milling, and it still works pretty good for manual milling.

I would say my short list is:

1. Vice.

2. Vice with parallels.

3. Clamps.

4. Side clamps, those clamps that hold the part at the base like
powerful fingers.

5. "pot it", or use low melting temperature metal to hold it.

6. Bolt or screw the workpiece to a plate.

For REALLY odd shaped workpieces, 6 cannot be beat. You get some
extra screw holes - big deal. The part is held to a plate with
complete access to all sides save the one face down. With most
parts, it hardly matters if there is an extra screw hole, and
if it does, it can be filled by various means.

--
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