Need to cut a V groove for a vise

[Pcmaker]

I'm making a replacement jaw for a vise that I need to cut a V groove into for clamping down on cylindrical objects

I have the part machined down to its final dimensions, I need to cut a V groove the whole length of it. It is .790 tall

how do I position my endmill to the center in order for me to cut a V groove? I have the endmill zeroed in on the top part with the DRO. I just need to know how much to lower the endmill so the cutting edge is right at the center of the part.

and I also need to know the X and Y positions in order to cut the desired size of the V groove. I assume I have to move the X and Y in equal parts in order to have an accurate sized V?

 

[RandyM]

This will tell you all you'll want to know.

 

[Parlo]

Sit the part in a vee block that is against an end stop. Cut a vee and then turn it around and cut with the tool in the same position, this will centralize the vee. Move either the X or Z so the cutter is touching both faces. Calculate the depth of the vee with a dowel pin and use this dimension to get the depth. Now move both the X and the Z by the same amount to achieve the vee depth.
You may find this video helpful.