Dial test indicator holder with micro adjust
Released 23.05.2026
Last Revision 23.05.2026
For the longest time I have used a half moon shaped indicator holder that I loosely copied off a commercial design - But it lacked two features that are important for my line of work: A fine adjust and a means of aligning the probe tip of the DTI with the centerline of rotation. The later feature is important when you use a DTI for edgefinding or to pick up very small features like bores or pins.
This design uses a commercial available fine adjust screw and nut from Thorlabs with a M4x0,25mm fine thread (See drawings for part numbers).
The screw pushes against a inset carbide piece in the holder, this prevents the screw from marring into the softer steel of the holder and in combination with the flexure joint creates a very smooth adjustment.
The DTI is clamped with a slit dovetail clamp, using a single M3 screw.
The large knurled section below the shank is meant to allow the holder to be spun by hand very easy, without having to touch the indicator or the arm, making it less likely to introduce an error that way.
Video
I created a two part video series building this tool:
Micro Adjust DTI holder - Part 1
Micro Adjust DTI holder - Part 2
Images
The DTI holder in the vertical spindle, used to center up on a PEEK workpiece held in a vise. In this orientation of the dial is very good, close to vertical, so no mirror is needed when sweeping around the part.
The DTI holder in use to center a pin sticking out the side of a workpiece held in the indexing head of my Deckel FP1 milling machine. You can see that the halfmoon is folded back to allow for clearance. This is a configuration that is often useful in a horizontal spindle in combination with limited access.
Drawing
dti_holder_micro_adjust.pdf - Annotaded drawing in PDF format.
dti_holder_micro_adjust.step - 3D Model in Step format - Use with care, some details are just placeholders in the model, like the dovetail for the DTI.
These drawings and the 3d model are released under Creative Commons CC BY-NC-SA 4.0, no guarantee for their completness nor correctness. If a obvious mistake occurs to you, feel free to mail me, I will upload a revised drawing.