My question is - how do you go about getting from a rough piece of stock to something that you can work with in CAD? That is to say, if I have a squared piece of 1/2" stock already, I can mount it to the table, set the Z and then specify in my program to cut down .1" or whatever. But what if I am starting with a rough piece of stock that first needs squared, then cut to spec (1/2").
Pre-CNC, I would have put it in the vice and cut one side, rotated it, and continue on until it was square, then measure and cut it to spec (1/2").
Do you write programs to true it up or do you just 'manually' do it in mach3 or something similar?
If at all possible, I hate to make up a couple of operations to prepare the rough stock. This is why I might prefer a slightly more expensive method of cutting the blanks, beginning with the best, such as cold sawing, band sawing, laser cutting, waterjet, plasma and Oxy-acetylene, then at the bottom of the list, shearing
For parts that will be machined in a vise, two parallel sides are very important if the part must sit on two parallels before you hit the Start button.
But, if one must begin with rougher shapes, then try to begin with a preparatory operation that adds value to the part, such as turning the OD of a round disk to final size, then put it the mill fixture, etc.
There are a few types of serrated roughing clamps that will bite into rough and slightly out of square surfaces. Toe clamps with serrated tips can be used to pull a part down onto parallels directly on the table for example.
Part of planning the machining operations correctly is achieving accessible locating surfaces for a second operation on the job. After the initial clamping on the rough, then you should, in the immediate machining setup, be trying to get some external planes to locate (clamp) on, or perhaps a hole pattern.
The preferred holding method for second operations would be the cheapest one with sufficient accuracy for the location. For example, use a vice, use a chuck or collet fixture, or if the part is really difficult to hold, a dedicated fixture may need to be made to grab the part. That's most often the fun part of machining, is the challenge of fixtures.
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)