Cutting a sign that required 3 bit changes

I designed a small sign that requires 3 tool changes. First cut, I zero XYZ with the touch plate and run the first cut with a 1/4 endmill to remove more material. Second cut, I change bits from 1/4 endmill to a 1/8 ball endmill. I Zero Z only because X & Y are still set to outside diameter. Because I changed to a 1/8 from a 1/4 bit I go to the settings and enter in the bit diameter when zeroing the Z. I start the cut and the bit goes around the inside diameter of my cutout a few times with a 1/8" gap between the bit and the side of the wood. It goes around 6 times until the bit finally touches the wood and starts taking off a very small amount. it goes around 2 more times then moves into the middle of my sign. At this point it should be going around and cleaning up my lettering but it starts cutting through my lettering and isn’t lining up at all with what I want it to cut. This is my second try at this sign, the first attempt I reset zero when I did my first tool change, and it didn’t know where it was suppose to be. The second time I watched a few tutorial videos on doing tool changes and I thought I had it figured out but obviously I don’t. What am I doing wrong? Thanks for your Help and advice in advance.

When you changed from the 1/4" bit to the 1/8" bit all you needed to do was rezero the z axis. You didn’t need to change any settings.


So going from a 1/4" down to a 1/8" bit, when setting up the toolpath, and bit your going to use, the tool path will take the size difference into consideration and adjust for the difference? I will give this a try tonight.
Thanks for the information.

Think of it this way, when you zero’d X and Y the first time you were actually zeroing the center of the router chuck. You want to keep that relationship for each successive bit, even if they are a different diameter.

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That does make sense when you think about it. I am running a sample cut right now with 2 bit changes to see it I now have a better understanding of the proper process. Thank You Paul for pointing me in the right direction. I hope as I learn more about the CNC process I will be able to help others in the Forum as well.

Thanks Again.