Bit Setter failiing at exactly the same Z consistantly

I just started running into a problem when using the bit setter. My Pro 4 XXL has been working well over the last couple weeks, but this morning that all changed.

When I try to start a job, the first thing that happens is the bit is moved to the bit setter corner and starts to descend. At exactly Z=1.72 inches above the surface, it just stops and C/M report “Probing Cycle Failed” I have restarted both the computer and the CNC several times, cleaned the contacts on both ends of the USB cable, modified the beginning Z axis in case there is something about that casing an issue), and the results are exactly the same. I’ve looked for any obstruction and have found nothing.
Not sure what is magical about z=1.72" but that seems to be the consistent fail point. Any Ideas?

What tool is installed?

How low is your router installed?

Post a photo of your Z-axis setup?

The tool is a 6 deg tapered 1/32"
Router has not moved from where it’s always been. I found that if I disable the bit setter and use th paper trick it seems to work fine so I started a 6 you parrallel cut and will measure the position of the spindle when It’s done.

I am pretty convinced that bit setter is the problem. I wonder if taking it apart and cleaning might work or add to the problem.


If the Bitsetter is failing on a probe check your BitZero magnet. If the magnet is grounded you will get a probe failure. The BitSetter and BitZero are tied together and if the magnet is grounded it will stop the probe from working.


I believe you need to slilghtly lower the VFD spindle in the mount so as to ensure that the shorter tool can reach as low as is necessary.

The magnet for the BitZero is not in contact with anything so that doesn’t seem to be the issue.

The spindle has been in the same position since the machine was built and it’s been working flawlessly. The fact that it’s stopping at the same position every time seems to indicate something mechanical or electronic. I can lower the spindle such that it touches the spoil-board so there does not seem to be any obvious obstruction. Also where this occurs (1.72" off the) which is way above where it is cutting now after I started the job using the paper method.

If I am not following you correctly, please let me know.


I moved the spindle down about a half inch and it made no difference. It stops at 1.72" I have a few cuts using the paper method and they turned out fine. I still think the BitSetter is the issue. My next step would be to try and take it apart unless you have a better idea.

This may be coincidence, but on my 5 Pro, the height of the Bit Setter when depressed is about 1.72" from the wasteboard top. If I were to go under 1.72" I’d either have missed the bit setter completely or drilled through it. Wonder if you took an update and lost some config settings? It’s pretty simple to reconfigure as a new machine in the current CM.

That’s a good idea Kevin, Too late in the afternoon for me, but I will try that in the AM. Something must have changed because the bitSetter has been working flawlessly for quite a while now. The device seems to simple to go rouge on me.

I’d certainly do that before disassembling the Bit Setter. I don’t know about yours, but the one on the 5 Pro has a red/green LED that indicates switch contact. If that’s changing color on pushing the top down, the thing is very likely to be working OK. Software is more likely.
Last evening, a Windows update hit in the last pass of flattening the wasteboard here - and it needed a complete computer (Surface Pro) power off/on and controller power off/on to get them back in sync. Anything less didn’t do it.

Another thing to try is putting a fan blowing on the controller.

Let us know what you find out at

Another good Idea. I guess I need to leave the controller cover off for now

There’s not much inside the Bitsetter that can go wrong… Just a spring loaded plunger with a steal knob on the end & a hall effect sensor(same one as for the other axis limit sensors).

The only problem I’ve encountered mechanically with a Bitsetter is the bottom knob somehow unthreading from the plunger - from vibrations I assumed. This caused the Bitsetter to be constantly triggered - so not likely your problem here.

1 Like

I’ve had to back-burner this problem for a couple days. I am approaching a deadline on a project and need to focus on getting that out the door. For now, the paper is working (and makes me really miss the convenience of the BitSetter). Thanks to the input on this forum, I have several things to try when the clock stops ticking.

BTW, my reasoning on taking the BitSetter apart is that dust might have gotten inside. (really a shot in the dark)

1 Like