Consistently setting Z-zero manually

I set my Z-zero a little unorthodoxly, but it works consistently, and it’s efficient enough for my needs. I do not have a bit setter. I thought about getting one, but I’ve gotten pretty good with my procedure, and I’m not sure it would save me much time.

To use this method, you will need a repeatable spot (XYZ) that you can go back to on your workpiece. This spot cannot be cut down, so if you are doing a fully caved piece, you would need to have extra uncarved material or use the spoil board as your Z-zero. I use the spoil board as my Z-zero if I’m doing a full carve. Basically you need a spot that is not going to change depth over the course of your program.
Now that we have that.

  1. Jog XY to your spot that you want to set Z-zero. I make this a spot where I change my bits if possible. (Instead of jogging, I usually run a quick macro in UGS to go back to the same spot).
  2. Install your first bit, but do not tighten it. Push the bit in all of the way and only hand tighten it using the push button on your router. Just enough to hold it from falling out.
  3. Jog Z down until your bit is about 1/8"(3mm) above the workpiece.
  4. By hand, loosen the collet until your bit slides down to the workpiece. You can use a finger to keep the bit from sliding down too fast. This will be your Z-zero.
  5. Tighten your bit using both wrenches.
  6. Set Z-zero in your control software.

Repeat this for every tool change.

Your Z-zero will be set at the same spot for every tool change. No guessing with paper pressure, no feeler gauge. Just gently let the bit down to the workpiece, or spoil board, and have a nice consistent Z-zero.


This is clever!
This assumes all the tools involved in the multi-tool job have a very similar overall length though ?

I used to do the same thing. As I accumulated (hoarded?) end mills, I found this to be more difficult, as @Julien suggests, with trying to minimize the unnecessary stickout. I actually had an endmill that would not reach the collet. I tried a 3D printed thing to set the end mills at a consistent length, and that had the same issue.
I then moved on to an aluminum foil version of a tool offset probe and then to the BitSetter. I still eyeball zero, though.

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No, not at all. You are resetting the zero in the control every time. The bit length does not matter. Each time you put in a new bit you jog Z to let the bit drop down to the workpiece about 1/8"(3mm) independently. Then you re-zero Z at the control.
I started using this method to keep the same zero when I went from a 1/8" clearing pass to a 60V. I would jog to Z zero and let the bit rest there. That’s not what I’m doing now. I don’t really pay attention to the current Z-zero now. I just reset it with each tool change.


That’s almost exactly the inverse action of the bitsetter with the same result, tidy bit of optimisation :wink:

I’ve been accidentally doing something similar with the new ER20 spindle jogging down and using the wasteboard to hold the bit at the height I want whilst I grab the collet spanners, might try just hitting Z zero instead of trying to remember to put the bitzero back on the workpiece.

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Oh I see, it’s not about the multi-tool job workflow, it’s an alternative to paper/feeler gauge/probe for touching off. Does it work well with teeny tiny endmills too? (just being curious)

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When you put bold text in your directions, I assumed I was meant to ignore that line and just guess what you were doing.


Ha, no it was bold to make sure not to forget to reset zero.

I don’t see why it wouldn’t work with any tool. I’ve used it for 1" facing mill to a 1/16" tapered ball.

I tried to do this for a while, and it worked ok for a single change, but for more than that I started to see cuts in the surface of the material just from the endmill resting there with the little force it gets trying to tighten the collet. I just use a simple zero probe in the same spot now and it’s a lot easier to get right. Nearly any zero probe works just fine if you’re willing to mess around as far as you are for a good zero, a different sender software that supports arbitrary sizes for x, y and z probes seem like a pretty small step… see UGS for something that does so. A cheap $5-10 z probe make this process pretty darn easy if you already know your top surface is totally flat which you probably can’t ever be totally sure of without a bunch of other measurements.

It can be a good reason to not use the top surface of the material as z zero - I almost never use the top surface unless I’m vcarving (lettering where I don’t want to touch the surrounding area, or pcb’s where I don’t want to surface the top of the material). If my sensitivity it to overall thickness, I use bottom Z, and surface the top of the material, never using the material itself for zero. Overall, this has prevented me from almost entirely avoided cutting into the wasteboard accidentally since I got religious about it.


While i do re zero for every tool change with the bit setter, mcmaster carr makes some nice bit collars for 1/4 and maybe 1/8 bits. They’re also pretty cheap.


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