Z Zero On Part??

RegisG

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I find lot of info about finding the edge of a work piece on a mill and can use my edge finder. But, what about finding the top of the piece to set the Z zero? My mill is manual but has 3 axis DRO (PM25MV).

Appreciate tip on zeroing the Z axis on top of part.

Regis
 
I use two methods. 1) With the spindle running, bring the tool down to just touch the work, just to where you can see it touch, and 2) with the spindle off, bring the tool down to a feeler gauge, then adjust to zero. Sometimes I use an actual feeler gauge, most times a piece of paper (~0.003)

EDIT: I should also say that before making the finish cut on the part, you should measure the part and take off the correct amount, don't rely on the initial setting of the Z zero position.
 
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I find lot of info about finding the edge of a work piece on a mill and can use my edge finder. But, what about finding the top of the piece to set the Z zero? My mill is manual but has 3 axis DRO (PM25MV).

Appreciate tip on zeroing the Z axis on top of part.

Regis

Depends on how accurate you want to be. If you want to get close use a piece of paper between your cutter and part. Lower your cutter until you can feel friction between the cutter and paper. Your cutter is now the thickness of the paper above your part.

More sophisticated methods are much more accurate but cost more. There are 3 axis electronic edge finders that advertise accuracy to .0005" or less. They work the same as a conventional edge finder but use a low voltage audible and/or light bulb to indicate when the edge or surface comes in contact with the edge finder tip.

Top of the line, IMHO, is a 3D Haimer Taster. Very accurate but very expensive. Basically it is a very accurate dial indicator with the capacity to locate in X, Y and Z.

There are other tools out there that have Z axis locating capability as well. Do a search on the web and you will find lots of videos on how to use the different tools available.

Tom S.

Edit - Do a "edge finder" and "touch probe" web search for videos. I did and found tons of info on the different types of tools used to find Z zero.
 
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another option I've always used (automotive machining) where the tolerances are +/-.005 is what's called a 123 block, the also sell metric ones.
Generally these are precision ground to size, but i've always checked mine anyways. the cheaper they are, the further from spec they normally are.

as far as pickup goes though it would be the same as mentioned above. either touch and go or friction feel
 
Thanks for all the tips. Didn't like the idea of scoring the top but, the paper or feeler gauge will meet my need.

Regis
 
For instances where your z axis reference will disappear, a suitable reference surface can be set up on the mill table and an offset calculated for your work. This works particularly well if you have a DRO but can also function using the dials.

To use, zero a tool or suitable pointer using one of the above methods and determine the z offset to your reference surface. Record that offset for future reference. Then every time you change a tool, determine the tool offset for the reference surface and correct for the offset between the reference surface and your part. For example if you zero on your part and the reference surface is 3" lower the the part zero (-3.000" in z direction), you would determine the position for a new tool just touching the reference surface and add 3.000" to bring it back to the zero reference point for your work piece.

The advantage doing this is that you can machine your original work zero surface and not lose yoou r reference and you can determine offsets for sensitive tools more easily. I used this technique years ago to successfully machine a part using tools as small as a .009" drill. My reference surface was the silver contact from a heavy duty relay wired to light up an LED on contact so I could overshoot the zero without fear breaking my fragile tools.
 
My reference surface was the silver contact from a heavy duty relay wired to light up an LED on contact so I could overshoot the zero without fear breaking my fragile tools.


Genius! :eagerness: You just solved my router tool zero problem. I'll post pictures in another thread in a few days.
 
On my PM25 and CO 12z, I lowered the head (with the cutter already installed in the spindle) until it is approx. 1/8"-1/4" away from the material. I then unlock the quill and 'gently' lower the quill by hand until I just touch the material with the cutter. Lock the quill, zero the Z-axis and then 'bump' the tool off the material slightly. I then move the cutter off to the side of the material, move the head back to zero on my DRO and then set my DOC from there. I do the same on my knee mill too.
 
I have a 2 axis cnc mill, I use a .020 shim, under the tool until it just drags using your quill stop, set the knee collar to 80, then retract the tool and raise the knee to 0, with the quill down it should just scratch the surface, keep in mind to use the same pressure on the quill handle, on mine I can feel the rack go slack and I know the quill is on the stop with the same pressure every time
 
another option I've always used (automotive machining) where the tolerances are +/-.005 is what's called a 123 block, the also sell metric ones.
Generally these are precision ground to size, but i've always checked mine anyways. the cheaper they are, the further from spec they normally are.

as far as pickup goes though it would be the same as mentioned above. either touch and go or friction feel

My cheap ebay 123s are more square and parallel than my brown and sharpe ultra precision 123s, just sayin
 
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