How do I recalibrate the Z setting in between tool changes?

CNC Machines Shapeoko
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I’m sure this is a dumb question, but how do I re-calibrate the Z setting for tool changes during the run? This project uses 3 tools.

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This is my largest project so far and it came out really well except the profile cut didn’t make it all the way trough by a hair.
I haven’t touched anything on the board so I should be able to do a path accurately again?
Thanks!
Don

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Hey Don,See if this helps, http://carbide3d.com/docs/tutorials/tool-change/

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Thanks Mark… heading there now.

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One thing you could also consider is using tool collars to hold your tools to the same “stick-out” as you change tools, and it’s definitely faster than touching off between tools. For this to work all your tools need to have THE SAME stick-out, and you want to make sure the collars you’re using are balanced, so you don’t introduce run-out and vibration to the tool.

A tool collar is just a press-fit ring of plastic or a small metal ring with a set-screw in it that you put on your tool so that every time you load it in the collet it sticks out the same amount—there are a lot of micro-tool providers who ship their tools with plastic depth rings on them by default. Precisebits has a write up on them here, and they offer tooling that comes with depth rings standard.

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Also, Harbor Freight sells a set of 1/8" shank micro drill bits with color-coded rings. They run about $9. However, I can’t attest to how well balanced they are at high speed. It looks like you may be using 1/4" end mills so this wouldn’t work in that case.
Jerry

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But, you shouldn’t use drills for milling—it’s not the right geometry for it, and they’re mechanically inefficient for it and likely to break a lot.

The guideline I’ve heard regarding drills vs. mills was that a good drill is still only 1/4th as effective at side-cutting as an end-mill, and an end-mill is 1/4th as effective at face cutting as a drill… but how that holds with modern tool geometries I’m not sure, maybe the differences are less severe.

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Yes. Good point. I should have mentioned that I use them in my Dremel drill press. Any thoughts on speeds and feeds for using drill bits with Nomad? I would think the spindle is too fast, but I’m not sure.
Jerry

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The Nomad tops out at 10krpm and can go as low as 1krpm… whereas your Dremel 4000 goes between 5krpm and 35krpm.

So the drilling feedrate range overlap is substantial, and the Nomad covers a lower range than the Dremel can.

It’s ultimately going to depend on your tooling and material for what the needed chip-load will be.

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