So I have been running Mach for a little. During this time I have learned a few things, mostly the hard way. Concepts sometimes hard to understand as a Noob to most of the processes.

   Now I am thinking easy repeatability for the majority of my tinkering. At present I place my vise in the middle of the table with the fixed jaw to the rear away from the operator, up near the column ( a G0704). I had been placing my stock in my vise on parallels etc and then using the lower left corner (of the stock) as my 0,0,0 point. This works but involves a constantly changing position. Then the light bulb pops on regarding the many articles read referring to referencing from the fixed or static jaw. Seems simple enough. Home machine, touch off to rear jaw on X & Y, set this point as zero in both of those axis. Great now we have a place that will always be the same as long as the stock is confined within the walls of the vise jaws, right? Doing this, does this necessitate moving the placement of my parts creation in the lower right quadrant of my CAD? It seems like it would. Not that it is a problem, just a realization (I think).  Edit: after reading my own question, if my stock extended outside the jaws on my X or Y axis, wouldnt it just be moving my stock into the adjacent quadrant in CAD?

   If that were true, wouldnt the same technique be used for Z reference off of the parallels? Place the parallels in the vise, zero off the top off the parallel and all moves in Z would be positive? Or just maybe starting above a known location? I am not having a problem keeping accurate (in my mind, results have all been in the .002-.004 range which is simply amazing to me so far) but could definitely alway see room for improvement and repeatability. Anything that would simplify set up would be great.

                                                           Sorry if this seems basic. I was used to sitting in the back of class in my school days to see the girls in front!
                                                           I have learned more on these forums regarding math, electronics, computers and machining than I ever did in schools.
                                                           I am not blaming it on the schools either.
                                                            

Unless you have a fixture with a set reference point the point of origin for a part will always be a variable point depending on the part.

If you use your vise AND the part can always be placed at the edge of the fixed jaw(X Y intersection) then the origin can remain constant. BUT you will have to plan it that way in CAD/CAM as well.

It does NOT matter where the POO(point of origin) is as long as both CAM and Mach3 agree as to where it is to be.

Just a thought, (;-) TP

I appreciate the input. At the present I dont use fixtures or should I say my stock is my fixture. I have made a fixture a few times but try to work around if possible. I can see as I get a bit better positioning repeatability on all sides will be critical (though I am thinking about using a rotary table to catch 4 sides without needing to change the set up of a part) If production was of a concern then I could see it being a necessity. More just trying to understand the positioning concepts better. It might have been more of a CAD or machining question.

If working with a vise, you will, most of the time, find it most convenient to do your CAD drawings such that the left rear corner of the blank is the drawing origin.  If you're doing a long piece, and it hangs over the end of the vise, get a "vise stop" which will give you a sold reference against which to align the stock, so your origin can still be at the top-left corner of the stock.  There are nice stops which mount to the vise, and to the table.  I made myself one like this:  http://www.edgetechnologyproducts.com/pro-stop.html  It's one of the most useful tools I've made.

Regards,
Ray L.

Just to add to Rays post, while those type stops are nice (and solid), I like a table mounted stop in many cases as it opens up those rear vise threaded holes just in case you're doing wide plates and you need to mount your rear jaw to the far backside of the vise. 

Dave

Thanks all. That clarifies a few things only to open more!