Use Touch Probe for double-sided milling?

I just received the C3D Touch Probe and am interested in using it to make two-sided milling easier. Is it possible to have CM4 probe a corner other than the bottom left one? I would think if it could probe the bottom right corner as well, I could flip over my work piece and have it re-set zero perfectly without having to use dowels? Or am I missing something dumb or obvious? I guess you could probe the bottom left corner both times, but that would require that the stock be perfectly measured and put into Fusion 360, right? In the past I haven’t worried about the stock size much in Fusion, I just model holes on either side of the object and have the Shapeoko drill them right into the wasteboard, which I then insert dowels into when I flip over the piece. That works pretty well, but of course is only as precise as my dowel-hole tolerance. But I’m thinking this can be easier and more accurate with the probe?

Thanks for any advice.


It is possible to probe in any direction (from any corner) by writing your own macros (gcode for doing the probing) and using a non-C3D gcode sender like UGS. “It is just software” as the saying goes. Dowels might be a simpler solution though.

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Even if you still use the locating dowel method for two sided milling, being able to set the z height accurately with the probe will be an advantage. When I do two sided milling I maintain the same x and y when I flip it. For the first operation my z is the top left corner of the stock. For the second operation, I use the surface of the bed as my z zero. That way I don’t have to precisely dimension my stock.


Thanks! I’ve used the same technique and figure the probe will definitely help make the Z height more accurate even with dowels. But I also figured since the corner finding is so accurate that I could skip the dowels and just reset X and Y as well, initially to the bottom left corner and then to the bottom right corner after it’s flipped. But if I can only easily probe the bottom left corner, I think that would still work but I’d have to measure the X dimension of the stock perfectly and input that into Fusion first. Or am I missing something?

Hmm. Well its always takes an awful lot of head scratching for me every time I do flip milling. But if you pick your zero reference points strategically, I do not believe that you need the stock dimensioned accurately in any direction. Let me see if I can explain.

Setup 1 uses the top of the stock, back right corner (this was from before I had a touch probe). This setup is used to drill the dowel locating holes as well as the first side milling operations. Because it was used to drill the dowel holes, the distance from the setup corner of the stock to the dowel hole is accurate.

Setup 2 uses the bottom of the stock back right corner. This means that I do not need to reset my x and y, because I’m using the same x and y point relative to my dowel holes that I used in setup 1. When I actually ran this job, the stock on the machine was wider in the x direction then I accounted for in the fusion model, but that was ok, because I did not reset the x and y and just let it hang off the back behind the x and y zero.

I’m not sure if I’m explaining it very well, hopefully the pictures help.


Yes, this is exactly what I’ve done so far. And achieved very good results. But with the corner probing I was thinking I could reset X and Y when I flip the material and not have to use dowels because the new piece could be anywhere on the wasteboard.

I see. Keeping my stock square and located is always a challenge, so I see myself continuing to use the dowel method. But please let me know if you find a better way to do two sided milling or if anyone else has recommendations. Maybe using a low profile milling vise?

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Off-topic, but…
@Plumshades, really nice work on the wands. Voldemort’s? And… whose?

@tito Thanks! Those are Harry’s and Hermione’s wands. At least thats what the models that I got from Thingaverse said. I made Harry’s using poplar and the Herminone one is maple.

Care to share the files used to create these wands? I would love to give double sided machining a shot and these would be perfect!

@winters636 I am trying to attach the Fusion 360 files, but I am getting an error saying I am not allowed to attached .f3d files? The stl files were easy to find on thingaverse if you search for Harry Potter Wand. I had to do some work in Fusion to get them CNC ready.

Do you have the gcode files and the information like bits used and stock size?