z axis work piece offset

[The CNC Noob]

Where do you guys generally get this measurement from using a hs1 ( z axis measurement)? I got the x and y but dont know what to do with the z.

[fuzzyracing1967]

Well with a few exptions for me it will allways be 0.I like to program off the top of the part so the z work offset stays 0 and the tool offset will be -.This way if you are drilling a hole 1. deep your program will be something like (G73 X0 Y0 Z-1. R.1 Q.25 F5. ).

[The CNC Noob]

The reason for asking is this. The person who programmed the part has moved on and I have never set up any parts that he has programmed. The setup guy went with him too. So is there any way that I can tell if it was programmed to be run with the z axis work piece offset set at 0? I looked at the z work piece offset on the previous job and it was set at -6.784 with a sentence written on the set up sheet that this is the distance from the center of the tombstone to the surface of the fixture. So now im not sure. Please any advice will be very helpful.
Thanks

[fuzzyracing1967]

What that meens is the program was writin as z0 was the center of the tombstone.So if you were to set your tool offsets off the surface of the parts and ran the program your tools would stay away from your parts by 6.784, so then if you put z-6.784 in the z WORK offset the tools would then cut the parts,ASSUMING THAT IS WHERE THE TOOLS SHOULD BE TOUCHED OFF.For instence we have a old hmc that the z work offset is allways -36.(center of table to spindle) and the z tool offsets are +,becouse tools are musred off line.Did I confuse you yet,,look at the program and the print and see if things match up,say a hole 1. deep does the program say z-1.? If it does then thats the surface to set tools off of.

[The CNC Noob]

Thanks alot that clears things up a bit. The setup sheet does say to touch all the tools off of the surface of the fixture and sweep a predrilled hole to get x and y work piece offset. It didnt mention z so I was lost. Thanks again.

[fuzzyracing1967]

Trust me I'v seen it done every witch way posible,sometimes with bad results,(ever hear a 2.5 hss drill brake whille trying to move in x while drill was still 4. in the hole,sounded like a shot gun).If you are not shore the best thing to do is put a + number in the z work offset and single block when you run the first peice that way you shouldn't crash right away .