Maslow4 - how to do bit changes?

Now that I’ve got my machine running (and the first cut came out almost perfect - within 0.5mm of the intended dimensions), I want to try out some more intricate designs. However, I ran into a challenge and a question…

How can I do a bit change in the middle of a project? On my original Maslow, I’d do a roughing pass, do a bit change while the sled hung on the chains ( and I could pull it way from the piece to do the bit change) then start the detail pass. With Maslow4, I’m using a horizontal setup. If I do a roughing pass, how can I change the bit and do the detail pass without basically starting over (disconnecting the belts, retracting all of them, extending them again, taking up the slack and rehoming)? Along with that being a pain the a** versus the original Maslow, I’m also worried the alignment to the piece has more of a chance of getting off.

I can imagine it would work reasonably well if there was a way to extend the belts enough to tilt the sled, change the bit, set it down and retract the slack without disconnecting from the frame.

Any thoughts?

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And zeroing the z-axis when changing bits is also extremely hard manually since it is almost impossible to see the bottom of the bit clearly. I only was successful doing it accurately if I did it before connecting the belts so I could see the bit in comparison to the bottom of the sled.

Post pictures!!! :heart_eyes:

Not sure :stuck_out_tongue:

How do you want it to work? We’ll make it work that way :grinning:

The way that I would do it right now is that I would make each tool a separate gcode file. After the first file finished I would raise the Z-axis all the way up, swap the bit, reset the zero height, lower it back down.

This is 100% doable.

I agree. It’s something that we need to work on making easier. I have some ideas. The easiest and probably best way to do it is to get touch plate support working so basically you could slip a piece of thin metal under the sled and it will detect when it touches to set the height.

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I 1000000% back this and would almost say it “should” be the very next thing implemented (the Original Malsow supported this, so I am sure it would be able to on the M4, just need to work it out in the FluidNC UI side.) This was very easy on the original as I had an 18-24" Metal ruler attached to the board with a metal clip on the other wire. The clip would attach to the bit, the ruler under the sled, and hit the Zero Z button (might have been Home Z), it would lower, make contact with the ruler (connecting the circuit), and set that point as “0” then raise up so the ruler and clip could be removed.

(Note: @bar, I am sure you already knew this, but was just wanting to post it as I know there are quite a few new comers to the group with the M4, so wanted to put it out there for them to understand. It took me a little bit to understand when I was looking to make that “upgrade” on the original design.)

I understand the theory and the how it works, I just don’t have a clue in the coding side to assist in any way!! Wish I could though!


given that the bit stickout is variable, that is the only way to be reliable.

I understand why you went with a very small opening in the sled, but if you had
a large enough opening, running the Z all the way down could give you access to
change the bit (like you do with a router table), especially with the kobalt
router. I may plan to carve away part of the sled to make that possible. If I do
I’ll send pictures.

David Lang

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a couple magnets on one of the support towers to hold the ruler would work well.

David Lang


That was plan A, but the big hole kept getting caught on things :confused:

And a couple more for the router wrench

why was that happening with the maslow 4 and not with the earlier versions?

David Lang

The way I zero out my M2 and plan on doing the same with the new machine is this. I have a piece of sheet metal that I place under the sled. Then I grab my multimeter and set it to continuity. Then I place one lead on the sheet metal and the other on the bit. I keep lowering it until I hear the beep. That gives me a perfect zeroing out everytime.


I kept having small parts that I cut go up into the hole and then not be able to get sucked into the dust collector so then they would fly around in there and hit the router bit.

YES I miss the Z touch from my Maslow. I see the FluidNC supports this, “we” just need to find a hardware port and code it.

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In the interim I just made this poor man’s z-probe out of a $5 continuity tester and a scrap of sheet metal. Just slide it under, attach the alligator clip to the bit, lower the bit until the light turns on and you are good to go.


Would it be useful to have buttons in the Maslow page’s “Z” dialog to save and return to “top”, “bottom” and “home” in addition to the current “up”, “down”, “define home”? I can take a whack at implementing that once I get my bearings better in the source code…

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I would love this so much. This has been on my ToDo list for weeks and weeks and never seems to make it to the top (pun intended).

I would also like to add a “Home Z” button which would run the z-axis all the way down and then reset the internal (mPOS not WCO) understanding of where the z-axis is. There currently is no way to do that and it’s a pretty big oversight.

I don’t think so. The problem is that you don’t insert the bit to the same depth
every time, and bits are different lengths, so there’s not a lot of value in
saving the numbers when you change anything (unless you start internally
tracking the difference between ‘min and max physical movement’ vs where zero is
currently defined)

David Lang


I noticed with my kreg router, if I tried to drive too low on the Z, the router
would slip in the clamps as well, yet another source of error.

David Lang

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Right, so a useful one to save would be “top” for changing bit, then maybe easier increments to get down quicker would be better. Something like 40mm, 20mm, 10mm, 1mm or whatever increments.

In any case, I’ll see if I can figure things out in terms of how to “Save” things from the ui (that is also something I need to learn to help with the calibration setup things too).

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ronlawrence3, On the left most tab of the interface there are Z steps like .1 1 10. Does that help any?


Yep, noticed those, and they work great. The UI I was talking about was the “z” on the maslow tab which is a little more clunky. I assume the idea on the maslow tab was to make it easier for phone/small format users to use, and not to replace the movement controls on tab 1.

I also see that you can set macros on the first tab which would also accomplish what I’m thinking with a little gcode (i.e. set z to whatever for bit change, then use the 10, 1 .1 to get back down to “home”).

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