An idea for a new Z probe "sensor"

I got an idea for a new probe. Instead of the crocodile clip and flat iron I am thinking of incorporating some kinda switch or switches all in a single unit that you place under the bit to zero it.

So I thought to use a floating piece of aluminum plate, floating on 4 springs salvaged from 4 ball point pens, the contacts could be 2 screwheads wired back to the Ardunino.

as you see these drawings are very basic but with a bit of fantasy you will get the idea.

The whole point of this exercise is to make this into a single unit.

I wonder if anyone has anything to add, or if you have seen any better plans.

regards Neal

Hmm, A precision switch that is normally open and closes when the bit presses down on the center plate.

when not being pressed on by the bit, the plate and the body are electrically isolated from each other by some sort of plastic or membrane at the top where the plate remains captured by the body, along the walls of the cylinder, and where the spring contacts underneath.

Some sort of design would be needed to keep the center plate from racking in the bore and binding.

When the plate it depressed it closes the circuit and this is at a known, repeatable height.

I can do general design in my noggin quite well but the real techie details and engineering are above my pay grade. I think all of this has some merit but it doesnt yet handle 3 axis zeroing like @CharleyThomas’s plate does. but for those who are not zeroing off the corner of a piece, it’s a neat idea.

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In version 6a3 of my G-Code Generator you can now set your X and Y axis at any point you choose on your material. You are no longer restricted to the front left corner. So if you like to have your starting point of your carvings in the center of your work piece you can. This is accomplished by entering an offset from the front left corner. Your touch plate is still stationed at the front left corner but by entering the desired offset, Your zero position will be at ANY location you choose.

Example: You have a 10 inch square piece of material and want your X and Y zero to be in the center. All you do is enter a 5 inch offset for the X and 5 inch offset for the Y and run the generated code.

You can also set the Z axis by itself by running the generated Z axis only code. You just flip the touch Plate upside down and lay it anywhere on your material you like and it will probe to the milled out area of the touch plate to set your Z axis to zero.

No fancy springs or other gizmo’s needed. All the magic happened in the formulas calculated by the spreadsheet.

The only requirement for a repeatable result is that you need to have a square corner on the front left of the material for the touch plate to “lock” in to.


There as some $10.00 Z axis touch plates available on Ebay that have a spring loaded center piece. I have read some of the reviews and they say that they are not very accurate and that the results vary from one use to the next. Definitely not what you want for a bit change or something that requires any level of precision.

You can avoid the problem of the touch plate “binding” in its shell by just getting rid of the shell. Get yourself a tinned piece of copper, get yourself a copper spring, solder the tinned piece to the end of the spring, and strap that spring to your wasteboard with a jig and crimp or solder your 0V wire to the bottom of the spring. It’d be incredibly cheap and repeatable, at least between tools on the same job. Whether the spring wears and sags or becomes stiff over months or years of use is irrelevant because any variation between tools on the same job would be negligible.

Yeah, I don’t feel that the spring loaded thing is necessary and just introduces more error modes.

I use a 1 IPM feed rate for probing to an aluminum gauge block and I really don’t think its dulling my bits. Just start the probe within 0.1" of the target. It doesn’t take that long to make contact at 1 IPM.

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Yup, simple is definitely better, Now that the fog of my morning migraine has lifted somewhat, I realize that I was chasing down a bit of a Rube Goldberg rabbit hole. When I thought further about it I realized that it was alot of effort to avoid attaching an alligator clip…

Yup, I figgered that one out about 24 hours after receiving the new touch “block”

I had not thought of using the offset function. this will be useful for those operations that require the utmost in centering accuracy. For most of what I do however I can simply eyeball it to within a few frog’s hairs of the center x mark and flip the block over.

You are the only person besides myself that I have ever heard refer to frog hairs. People often ask me how I’m doing and I reply “Fine as a Fog Hair”. I get come very curious looks.

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You can find frog hairs in the apothecary section right next to the chicken lips and the eye of newt…

OK I’ll bite, what is RCH?

Just for kicks I googled it and I was close, I was thinking “royal” , but it was “red”…:sweat_smile:

Oh My :smiling_imp:

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Lots of ideas/discussion here, I am starting out on my annual boating holiday next week and will be away for most of the summer so I will have plenty of time to think it through.

I am toying with the idea of 3 bolt heads but I will maybe have to use diodes or relays. 3 screwheads is ideal (in theory) 4 can (or will block in theory) 3 is repeatable and accurate.

The aluminum jamming I suppose is a problem. I think a good session with round over filing will do the trick, and a very short “stroke length” of say 1/4 inch (6mm) and for those who tittered at “stroke length” they can wear this D hat and go and stand in the corner

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hee hee, he said stroke length.

putting on my hat…

Look again, he said it twice… Got my hat on too!!

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