Re: Workshop/Tools/Parts
 

Obviously a lathe / mill is going to give you a flatter face than any saw, but it's still nice for roughing out stock to start with a semi-flat face to clamp on.

I like horizontal band saws - if I was starting a shop from scratch and could only have one big saw, I would probably get a portable band saw with a table stand for vertical cutting and then a full size horizontal for cutting out stock and whatnot.

Re: Workshop/Tools/Parts
 

Important for a number of reasons. Minimizing stock size needed for a part. Minimizing variation in size from part to part, which is more important for CNC since you're taking a fixed number of passes and you don't want to program for the length of Part A then find out Part B is .125" taller (an exaggeration, but it can happen). An easier scenario that will screw everything up is a part that has left and right edges that make it a parallelogram, due to non straight cuts, which can no longer act as registers for a fixed stop on the vise, since your origin is moving dramatically with each part change.

Sometimes based on the size stock you have on hand, you need to hold the cut faces in a vise, not the stock edges. The more parallel they are to each other the easier that is. Sometimes you cut bar stock and you need to stand it up on the edge that was cut. Again, the more perpendicular to the stock edges, the better.

When using the lathe sometimes you'll have pieces that are too large in diameter to hold with jaws in their standard configuration and you end up flipping the jaws and holding the part on the stepped portion of the jaws. If your bottom surface sitting against the step on the jaw isn't flat you end up with a lot of runout on the part, which is a PITA. Likewise if you're cutting something too short to be clamped by the full length of the jaws you don't get proper self centering of the part and you need to stick parallels or something else against the face of the chuck and seat your part flat against them. If the part doesn't have a flat face you get the same runout problem.

Re: Workshop/Tools/Parts
 

Okay I can see that.

However usually if I want 2 or more pieces to be extremely close in size I palatize or stack them and that way any runout is likely uniform.

For your lathe example with, I assume is a 4 independent jaw chuck, I can see that you're trying to save an operation.

Re: Workshop/Tools/Parts
 

Even if you stack two pieces and cut them on a vertical bandsaw that doesn't mean the cuts are actually straight. Anyone who is cutting any quantities greater than 2-3 of barstock or tube to go into a mill or lathe would be much better off with a horizontal from a cut quality, squareness, and time standpoint.

I'm referring to a 3 jaw self centering chuck. If you are only clamping onto say 1/4" of length on the part you can easily end up with the part skewed in the jaws. You need to be clamping onto substantially more to guarantee that the stock is coaxial to the jaws (at least without tapping it into alignment).

Re: Workshop/Tools/Parts
 

Sure but if you stack and bolt 2 or more plates to the surface of a sacrificial plate on a mill that usually doesn't matter.

As a matter of practice I usually try to run an indicator (coaxial, reference object, edge finder, or dial test) against anything I put in a lathe chuck. Either on the outside diameter or the inside diameter where that is applicable. I've worked on too many saws that wouldn't cut straight enough I could trust them. For example a cheap Chinese horizontal bandsaw with no hydraulic down feed even under proper tension might not cut straight from the pressure angle of the blade changing from the weight of saw assembly around the blade. This becomes less an issue on that same saw if you put a hydraulic downfeed retrofit on it like I did in my home shop (it's a surplus pneumatic piston rigged with hydraulic fluid).