This is a new model based on limitations of the model below. The large indicator has a large offset from the nozzle location so it cannot reach the entire printable area. Most notable, it cannot reach the rear tramming screw.
This should fit any standard dovetail test indicator. It is flexible enough to snap the dovetail in place from the front as opposed to sliding in from the top or the bottom which I found difficult because I chose to reference the main body as opposed to the top of the dovetail. You can wait and mount the indicator after the holder in installed in the machine. If you mount the indicator first, make sure you clear the mounting screws.
As you can see from the photos, the standard-length probe is very nearly aligned to the hotend tip location so you can measure the entire printable area. As well as position it the tip directly over the tramming screws. This will allow most people to do a far more accurate job than simply trying to just touch the hotend as provided by BL.
I cannot say it will work for everyone, but the bed sensors appear to be sensitive enough to zero at the upper limit of the indicator travel which makes it really easy to home the machine and move all the axis to take your measurements.
It is easy to record a grid by using the front panel controls if you are attempting to shim a warped bed. My suggestion is to do 10 or 20mm steps and video record the dial at each location, then transcribe later.
I am printing it in the use orientation. This gives good layer orientation for the critical dovetail and mounting surfaces. It may cause some problems with the mounting holes, but they are easy to clean out with a 1/8inch drill bit.
It requires a test indicator. They are very easy to find by searching Amazon with the name ‘test indicator’. There are a tremendous variety of resolutions and cost. You probably want a 0.0005" or 10um resolution, with the standard short probe tip.
You will need a M3x16L screw and nut to clamp the indicator.
The author remixed this model.