Center the servo
Power the system and command the servo to the intended neutral position.
AI-Assisted Design · 3D Printing · RC
KISS 90° Servo Jig.
Keep It Simple, Stupid.
A simple 3D-printable jig for sanity-checking an RC servo horn at approximately 90 degrees to the servo case during setup.
One printed part
No assembly
No extra hardware
Quick visual reference
The 88.5° problem
Looks square.
Probably square.
Wait... is that actually square?
Servo-horn setup is one of those RC jobs that should take about thirty seconds. Center the servo, install the horn, move on. Except eyeballing 90° works right up until you stare at it long enough to start negotiating with yourself.
Because eyeballing 90° works right up until you spend the next twenty minutes wondering whether it is actually 88.5°. :-P
How it works
Center. Place. Align.
Check. Finish setup.
The jig is a visual reference, not a replacement for normal servo setup. Use it while the servo is at its intended neutral position, get the horn as close to 90° as the spline allows, then finish any required electronic or model-specific adjustment normally.
Place the jig
Seat the printed jig squarely on the servo case and reference surfaces.
Set the horn
Install or reposition the horn as close to 90° as spline indexing allows.
Check alignment
Use the jig's physical reference as a quick visual sanity check.
Finish normal setup
Apply required sub-trim and complete the model's normal linkage, travel and direction checks.
Keep it simple
One narrow problem.
One simple answer.
This project does not need pivots, detents, ball plungers, bearings, or seventeen revisions. It exists to make one small bench task less annoying and then get out of the way.
What it is
- A reusable physical 90° reference
- A quick RC build-bench sanity check
- A simple printable object with no assembly
- A convenient aid when a true 90° horn relationship is desired
What it is not
- A precision calibration instrument
- A guarantee of perfect servo geometry
- A replacement for servo centering or sub-trim
- A substitute for model-specific setup instructions or final control checks
Actual use
It makes more sense
when you see it.
The jig sits on the servo case and gives the horn a simple visual reference. That is the entire trick. The real printed tool explains itself faster than a paragraph of CAD terminology.
Close enough mechanically.
Finish it electronically.
Servo splines may not let the horn land at a mathematically perfect 90° position. Get the horn as close as the physical spline allows, use the jig to verify the relationship, then apply whatever electronic sub-trim or controller setup the model requires.
PLA? Generally fine for a normal shop/build-bench jig.
PETG? Also fine if that is what you prefer to print.
Bad fit? Do not force it onto the servo. Verify the print and the intended reference surfaces.
AI-assisted CAD
Not an AI case study.
Just a useful little tool.
AI helped translate the bench-tool idea and physical requirements into printable geometry, iterate the design, and organize the project documentation. Physical fit and usability still determined whether the printed part actually worked.
Build resources
Print it.
Check it. Move on.
The public GitHub repository is the authoritative source for the printable files, usage guidance, license, and disclaimer. The website explains the idea; GitHub has the files.
STLUniversal printable geometry for use with compatible slicers and printers.
Bambu Studio 3MFA prepared project for builders who want a convenient Bambu Studio starting point.
Reference photographyPrinted-jig and real-use images showing what the finished tool looks like and how it sits on a servo.
README, license & disclaimerDetailed use notes plus the project's personal/non-commercial license and fitment guidance.
Alignment aid, not calibration instrument. Verify that the servo is centered, confirm the jig fits and seats squarely, and follow the setup requirements for the specific model and electronics. Printed dimensions can vary with printer, material, slicer settings and calibration. Free for personal and non-commercial use under the project's repository license; see GitHub for the complete license and disclaimer.
#FPD
Function. Print. Destroy. Same acronym, different project. This one survived by refusing to become more complicated than the problem.
Keep It Simple, Stupid
Thirty-second problem.
Thirty-second tool.
Center the servo. Set the horn. Check 90°. Finish the normal setup and get back to building the model.