How To Find “Edge” on Z Axis

[Maplehead]

Hi All
I use my wobbler all the time to find the edge of material.
However, let’s say I am milling a series of non-through holes along the top of a bar. The holes are shallow but I want them all to have the precise depth.
How do I set the mill at the exact same start depth for each hole?
Right now I watch closely as I slowly bring down the mill until I see the very start of material being removed and then I stop and lock my Z axis and switch to using the fine feed that is already set at zero.

 

[Cadillac]

You can take a know thickness like a piece of paper. Put on top your part. Bring spindle/cutter down to touch paper. Then you know the distance to your part. You could have hen use a dial indicator mount and zero to table and then you can see what you move on the z axis. They do sell z height gauges but many ways to get around it.

 

[Canus]

Maplehead, you state "Right now I watch closely as I slowly bring down the mill until I see the very start of material being removed and then I stop and lock my Z axis and switch to using the fine feed that is already set at zero." Do you mean that you are raising the table until you get contact then lock the Z axis? If so you are good to go. I am assuming you have a DRO on the quill. The method Cadillac covers is also acceptable and widely used.

 

[Maplehead]

I wish I were raising the table but my mill is the lowering the head style. But yeah, that’s what I do. I still get size differences in the holes however. No DRO for Z.

 

[markba633csi]

Assuming your fine feed has enough travel to do the hole depth + a little more I would keep the z locked and do it all with the fine feed and touch off with paper or a probe
Your mill is a square column correct?
mark

 

[Maplehead]

Yup, square column.

 

[Cadillac]

The fine feed screw is probably not precise enough to hold accurate movements. Get yourself a 2” travel dial indicator. Figure out a way to mount to machine to read spindle travel. That’s your cheapest route. Even a 6” dro just a little more mounting involved but I wouldn’t rely on the screw for depth readings. That’s just me though.