Accurate Bed Level Aid

For those of you with access to a Touch tool (Height gauge) with an R8 (0.75") shaft and would like to level your taz 4 bed with precision (accurate to within .001") attached is my .STL file and images for a compression fit rail mount that will hold the device.

Note: your X Axis rails must be level for this to work properly.

For anybody looking to make their own:

The X Axis rails are 80mm apart from top to bottom (Center of each circle 70mm apart)
Each tube is 10mm thick

level device.stl (101 KB)
bl side.jpg
Bed Level.jpg

Looks interesting. What make / model # is the height gauge?

The dial says it is an H&Hip dial gauge. I purchased it along with my PCNC1100 from tormach. Link to the dial gauge is here:

I printed this one from Thingiverse and Used a meter from Harbor Freight

I used that one too, including buying the HFTools digital indicator.
After building the slot between the two tabs, where the dial indicator’s mounting tab goes, is 5mm, while at least here in Seattle, the HFTools part has a 1/4" thick mount tab. Luckily my CNC router can make a proper 1/4" slot, so after that I was set. Been using it to good measure and good results. While it might be nice to have 0.0005 inch accuracy, truth be told I noticed my bed has a bow in it…only about 0.03mm, but a dang bow anyway. So maybe that extra re$olution isn’t worth it in this application.



The bow you are seeing could be the weight of the extruder causing the x-axis rods to bend downward. Does it seem like the glass is bowed upward in the center of the bed?


see video I made:

Thanks for the vid. Do you know if your indicator gauge mount will work with this indicator:


What are the units on your gauge? Is that a 0.07 mm difference between the center and side of the glass?

Here’s the whole thread:

In inches the difference was 0.007 from edge to center. But that’s with the added weight of the gauge.

I’ve scrapped that mount in favor of a different style. There’s no way my mount will work with a different dial indicator.
I went with something more similar to this one:
I just retro-fitted that design to fit my gauge.

Yes, that’s exactly what I did too. The bowing is evident as a LOW spot (more space bed-to-nozzle) in the middle. If it was the rails, it would seem like less space (bed-to-extruder) would be in the middle if it was a rail bowing issue. Nope, it’s the bed.

Is it possible to topographically map the build surface with a probe utilizing Marlin?

Every bed is different and there are so many variables involved in getting that first layer down “good enough” that it would be immensely helpful to just map the surface and let the software iron out the imperfections.

Not entirely, but that’s sort of the idea behind the auto-bed-leveling features that employ the flip-down microswitch. I think they just use 4 or 5 points, not like every 2mm or anything :wink:

Just put together my first KITTAZ and I have a similar bow in the Y axis glass, only mine is larger: 0.03" 0.762 mm difference between the X travel edges and the center, measured at room temp. Its bowed high in the center and only along the X axis direction. I was thinking this is from sticking on the heater pad with adhesive. I did this on a soft surface. Laminates always bow.
I measured with a dial indicator stuck onto the extruder stepper case with double-sticky thin foam tape. Worked great. Very repeatable.

It likely is not bowed. The x rods actually flex with the weight of the extruder when it is in the center of the x axis. Mine lowers the extruder tip by about 0.01 inches.

Turn your glass bed 90 degrees and see if the measurements are pretty much unchanged. If the bed was bowed, the error would move to the Y axis when you rotate the bed.

gjamesnvda ,

The distance of my hot end to the center of glass is 0.15 mm shorter than the distance of my hot end to the 4 corners of the glass, but your measurement of 0.762 mm seems extraordinary. Please verify there was no compression in the foam tape during your measurements? Can you take a picture of your dial indicator setup?