Fusion 360 Add-In
Fastener Suite
Every fastener operation in one panel.
Threads, heat-set inserts, nut traps, and tap drill sizing — four tools that belong together, finally together. Full timeline round-trip editing included.
What's inside
Four tools. One panel.
Fastener Suite lives under Solid → Create as a single docked 680×840 px panel. All four tabs are always one click away.
Threads++
Apply threaded features to cylindrical faces with 6 standards, 5 tolerance presets, optional countersink, and custom thread profiles.
Heat-Set Inserts
Resize holes to the correct press-fit diameter for brass heat-set inserts, with optional lead-in chamfer and multi-hole batch apply.
Nut Trap
Cut blind hex pockets or side-loading slots for captured nuts. Supports ISO 4032, ISO 4035, and DIN 934 standards M2–M12.
Tap Drill
Resize holes to tap drill or clearance drill diameter. Live diameter preview before applying. Metric and inch standards.
FDM / 3D Printing
Built for 3D Printing
Why FDM holes are always undersized
Fused deposition modelling introduces three compounding sources of dimensional error that all shrink hole diameters:
- Plastic shrinkage — molten plastic contracts as it cools, pulling the bore inward
- Layer line adhesion — adjacent perimeters bond slightly outward into the hole cross-section
- Elephant foot — first layers squish outward on the build plate, tightening holes at the base
The combined effect is typically 0.1 mm to 0.3 mm of under-size depending on material and printer calibration. Standard thread tolerances are designed for machined metal — they are too tight for printed parts straight off the bed.
How each tab addresses 3D printing
- Threads++ — use the Medium (+0.10 mm) or
Coarse (+0.20 mm) tolerance preset for FDM-printed holes.
The preset expands the minor diameter so taps or screws actually fit.
print_thread_data.jsonships with FDM-optimized minor diameters for M2–M12 ISO Coarse. - Heat-Set Inserts — the standard for structural FDM assemblies (used by Voron, Prusa, and every serious maker build). The Voron/Generic standard is the go-to for hobby 3D printing. Brass inserts give you full metal threads in plastic — far stronger than threading into plastic directly.
- Nut Trap — ubiquitous in FDM design. Drop M3 or M4 hex nuts into pockets during assembly. The 0.20 mm hex clearance default is tuned for FDM tolerance. Side-loading mode lets you add nuts to already-printed parts without pressing them in from above.
- Tap Drill — drill/tap is viable in PLA/PETG with slow feeds. Useful when wall thickness is too thin for a heat-set pocket. The 75% thread engagement setting (standard tap drill) is appropriate for plastics.
Practical tips for FDM
- Start with Medium tolerance for PETG/PLA; go Coarse for flexible filaments or large-diameter holes
- For structural M3 connections: heat-set brass insert is always stronger than threading directly into plastic
- Print tap drill holes 0.1–0.15 mm smaller than specified — FDM comes out undersized, so the tap will hit the right engagement
- Back-side nut traps should add 0.2–0.3 mm to hex clearance if your printer has notable dimensional drift
Tab 1
Threads++
Apply threaded features to cylindrical faces or edges. Internal vs. external threading is auto-detected from face normal direction. Select multiple faces in a single command.
Panel mockup — Threads++ tab active
- ①Face / Edge selectionClick a cylindrical face or circular edge. Internal vs. external thread direction is detected automatically from surface normal. Multi-select supported.
- ②Standard6 standards: ISO Metric Coarse, ISO Metric Fine, UNC, UNF, BSW (Whitworth), BSP Pipe.
- ③SizePopulated after Standard is chosen. Size list is filtered to only valid entries for that standard.
- ④ToleranceNominal = exact spec. Fine +0.05 / Medium +0.10 / Coarse +0.20 mm adds clearance on internal threads. For FDM-printed holes, use Medium or Coarse.
- ⑤CountersinkAdds a chamfered lead-in at the top of the thread. Depth and included angle (10–170°) are configurable. Supports both ends of a through-hole simultaneously.
- ⑥Modeled ThreadOn: generates actual helical geometry visible in section view. Off: schematic representation, lighter on large assemblies.
Thread standards
| Standard | Size range | Common use |
|---|---|---|
| M Series ISO Metric Coarse | M2 – M24 | General-purpose metric fasteners |
| M Series ISO Metric Fine | M2–M6 (small fine), M8–M24 (fine) | Precision / vibration-resistant |
| UNC Unified Coarse | #4-40 – 1"-8 | Standard US fasteners |
| UNF Unified Fine | #4-48 – 3/4-16 | US precision / automotive |
| BSW British Standard Whitworth | 1/8" – 1" | Legacy British machinery |
| BSP G Parallel Pipe (ISO 228) | G1/8 – G2 | Fluid / pneumatic fittings |
Tolerance presets
- Nominal (0) — exact per standard
- Fine (+0.05 mm) — snug fit
- Medium (+0.10 mm) — typical print tolerance
- Coarse (+0.20 mm) — loose fit / thick coating
- Custom — arbitrary mm offset
Internal threads expand; external threads shrink.
Countersink options
- Optional chamfer at thread entry
- Configurable depth & included angle (10°–170°)
- Auto-detects topmost entry edge
- Supports multi-hole countersink in one operation
- Both ends of through-holes supported
- Deduplication prevents double-chamfering when edge and face of the same hole are both selected
Custom thread profiles
Define custom thread families — name, pitch, major/minor diameter, and angle.
Profiles are saved to FastenerSuiteLibrary.xml in Fusion's ThreadData
folder and persist across sessions. The Clear Thread Library button
removes the file when you want a clean slate.
Tab 2
Heat-Set Inserts
Resizes a cylindrical hole to the correct press-fit diameter for brass heat-set inserts. Pick a standard, pick a size, click OK — the geometry updates automatically.
Panel mockup — Heat-Set tab active
- ①Hole selectionSelect the cylindrical bore to resize. The bore is enlarged to the press-fit diameter for the chosen insert standard.
- ②StandardVoron/Generic vs McMaster/Shapelock — different press-fit ODs. Choose the brand matching your inserts. Voron/Generic is the most common in hobby 3D printing.
- ③SizeM2–M6. Match to the heat-set insert you're installing. M3 is the most common in FDM structural assemblies.
- ④Press-fit clearanceExtra material added to the bore beyond nominal (default 0.10 mm). Increase slightly for flexible filaments or large prints with dimensional drift.
- ⑤Lead-in chamfer0.5 mm equal-distance chamfer at the bore entry. Helps seat the insert perpendicular — critical for accurate assembly.
Supported standards
| Standard | Sizes | Notes |
|---|---|---|
| M-Series Voron / Generic | M2, M3, M4, M5, M6 | Voron project press-fit diameters |
| M-Series McMaster / Shapelock | M2, M3, M4, M5, M6 | McMaster-Carr catalog dimensions |
Voron M3 and McMaster M3 have different press-fit diameters. Verify the correct standard matches your actual insert supplier.
Key features
- Configurable press-fit clearance (default 0.10 mm)
- Optional 0.5 mm equal-distance lead-in chamfer
- Multi-hole apply in a single operation
- All chamfers batched into a single Fusion feature
- Timeline attributes store full parameters for round-trip edit
Tab 3
Nut Trap
Cuts a hex pocket for a captured nut in two modes, with configurable clearance and support for three international nut standards.
Panel mockup — Nut Trap tab active
- ①Face selectionThe face where the pocket is cut. For back-side mode, this is the face opposite from where the bolt enters.
- ②ModeBack Side: blind hex pocket. Side-Loading: pocket + slot so the nut slides in from the edge — useful when you can't press a nut in from above.
- ③StandardISO 4032 (full-height), ISO 4035 (thin), or DIN 934. For FDM builds, ISO 4032 is the standard choice.
- ④SizeM2–M12. M3 and M4 are the most common in FDM printed enclosures and structural parts.
- ⑤Hex clearanceExtra space beyond the nut hex across-flats (default 0.20 mm). FDM prints may need 0.25–0.30 mm on printers with larger dimensional tolerance.
- ⑥Slot direction (Side-Loading)Auto-detects nearest wall. Override by selecting a specific planar face, or use angle offset to rotate the exit slot.
Pocket modes
Back Side
Blind pocket cut into the back face of the part. Clean, no exit slot.
Side-Loading
Pocket plus an exit slot so the nut slides in from the edge. Slot direction is auto-detected toward the nearest wall, or select a planar face explicitly. Use the slot angle offset (degrees) to rotate the exit direction.
Nut standards
| Standard | Sizes | Type |
|---|---|---|
| ISO 4032 | M2 – M12 | Standard hex nut |
| ISO 4035 | M2 – M12 | Thin hex nut |
| DIN 934 | M2 – M12 | Standard hex nut (DIN) |
Configuration
- Hex clearance: default 0.20 mm (configurable)
- Extra depth configurable beyond nut height
- Slot angle offset rotates exit direction in degrees
- Manual slot direction face selection overrides auto-detect
- Custom nut sizes available via the Settings tab
Tab 4
Tap Drill
Resize a hole to the correct diameter — either a tap drill for 75% thread engagement, or a clearance drill for bolt pass-through. Displays the target diameter in preview before applying changes to the geometry.
Panel mockup — Tap Drill tab active
- ①Bore selectionSelect the cylindrical hole to resize. The bore diameter is changed to match the calculated tap or clearance drill diameter.
- ②ModeTap Drill: size for 75% thread engagement (standard for most tapping). Clearance Drill: oversize for bolt-through fit.
- ③StandardISO Metric Coarse/Fine, UNC, UNF.
- ④SizeThread size. The calculated diameter is shown in the preview before you click OK.
- ⑤Fit (Clearance mode)Close / Normal / Free per ISO 273 / ASME B18.2.8. Normal is standard; Free gives more assembly clearance. Greyed out in Tap Drill mode.
- ⑥Target diameter previewDisplays the calculated diameter before applying. Verify this matches your drill stock before committing.
Sub-modes
Tap Drill
Resize hole to tap drill diameter for 75% thread engagement. Correct for hand tapping or thread-forming.
Clearance Drill
Resize hole to bolt clearance per ISO 273 / ASME B18.2.8. Three fit classes: Close, Normal, and Free.
Supported standards
- ISO Metric Coarse: M2 – M24
- ISO Metric Fine: M2 – M24
- UNC Unified Coarse: #4-40 – 1"-8
- UNF Unified Fine: #4-48 – 3/4-16
Target diameter shown in the panel before you click OK. Applies the resize directly to the hole geometry on confirm.
Technically notable
Timeline round-trip editing
Every feature created by Fastener Suite stores its full parameters as Fusion
attributes (group: FastenerSuite). Double-click any Fastener Suite
feature in the timeline and the panel reopens pre-filled with the original settings
— change what you need and click OK.
- Intercepts
FusionDcThreadEditCommandandFusionDcExtrudeEditCommand - Related features grouped in named TimelineGroups (e.g., thread + countersink, heat-set + chamfer)
- During edit: original thread suppressed; deleted on OK, unsuppressed on Cancel
- Works for all four tabs — threads, heat-set, nut traps, and tap drill
Getting started
Installation
Fastener Suite requires Fusion 360 (Windows or macOS). Python 3.x is bundled with Fusion — no separate install needed.
- 1
Open Scripts and Add-Ins
In Fusion 360, navigate to Tools → Add-Ins → Scripts and Add-Ins.
- 2
Add the folder
Click + in the Add-Ins tab and select the
Fusion360-threading-suitefolder. - 3
Run the add-in
Select FastenerSuite from the list and click Run.
- 4
Access the panel
The Fastener Suite button appears under Solid → Create. Click it to open the docked panel.
- 5
Runs on startup (automatic)
The manifest sets
runOnStartup: true— Fastener Suite loads automatically every time Fusion opens.
Advanced
For power users
Fastener Suite is data-file driven. Every lookup table is plain JSON — open it in any editor, change values, save, and the change takes effect on next use.
Data files
FastenerSuiteLibrary.xml— custom thread profiles (ThreadData folder)FastenerSuiteTemp.xml— session-only threads (deleted after first use)custom_profiles.json— user-defined thread familiesheat_set_data.json— press-fit diameter tablesnut_data.json— hex nut dimensions by standardtap_drill_data.json— tap and clearance drill tables
Each tab has a Config file button at the bottom that opens the relevant JSON in your OS default editor.
LOG_COMMANDS flag
Set LOG_COMMANDS = True in the entry point
(Fusion360-threading-suite.py) to log every intercepted command ID
to fastener_suite_cmdlog.txt.
This is useful after a Fusion 360 update — Autodesk occasionally renames internal command IDs. Trigger a thread edit with the flag enabled, inspect the log, then update the intercept list with the new IDs.
3D-print thread params
print_thread_data.json contains FDM-optimized thread parameters for
M2–M12 ISO Coarse with print-tolerance adjustments. The file is loaded by the
add-in but not yet exposed as a UI tab — power users can reference the JSON
directly and apply values manually.
Thread library fallback
Fastener Suite writes FastenerSuiteLibrary.xml to Fusion's standard
ThreadData folder. If that folder cannot be found (unusual install path),
the add-in falls back to the closest-matching built-in standard thread.
The thread still applies — but custom tolerance designations won't persist
to Fusion's thread database until the ThreadData path is resolved.
Timeline internals
- Attributes stored under group
FastenerSuiteon the feature body - All parameters serialized to JSON strings in the attribute value
- TimelineGroup names follow pattern: FastenerSuite_Threads_<timestamp>
- Edit path: intercept → suppress original → rebuild → delete on OK / unsuppress on Cancel
Support
Troubleshooting
"ThreadData folder not found" error
This appears when Fusion 360 was installed to a non-standard path. The thread feature still applies, but the custom tolerance designation won't persist to Fusion's thread database.
Fix: Verify Fusion is installed in the standard location for your
OS. On Windows this is typically %localappdata%\Autodesk\webdeploy.
Once ThreadData is accessible, custom profiles save normally.
Timeline editing stops working after a Fusion 360 update
Autodesk occasionally renames internal command IDs between releases. When this happens, the timeline intercept no longer matches and double-click editing breaks.
Fix: Set LOG_COMMANDS = True in
Fusion360-threading-suite.py, trigger a thread edit manually, then
open fastener_suite_cmdlog.txt to find the new command IDs. Update
the intercept list in the add-in source with the new values.
Countersink fails on non-standard bore topology
The countersink operation requires a distinct planar entry face at the bore opening. Some imported or complex geometry doesn't have a clean planar face at the hole entry.
Workaround: Apply the thread first without countersink enabled, then add the chamfer manually using Fusion's built-in Chamfer tool on the entry edge.
Side-loading nut trap slot direction is wrong or ambiguous
Auto-detect picks the nearest wall as the slot exit direction, which may not be what you want on parts with complex geometry or when the nut needs to load from a specific direction.
Fix: Select a planar face explicitly via the
sel_slot_face input to override auto-detect, or use the
Slot angle offset field to rotate the exit direction by a
precise number of degrees.
Custom tolerance raises a ValueError
Extreme tolerance values can push the minor diameter to 0 or below, or push it above the major diameter — both are geometrically invalid.
Fix: Use a smaller tolerance value. For reference, typical useful range is roughly ±0.5 mm for most thread sizes. If you need a very large clearance, consider using the Tap Drill tab's Clearance Drill mode instead.
Multi-face thread apply with countersink double-chamfers some holes
When selecting faces for multi-thread apply, it's possible to accidentally select both the cylindrical face and the entry edge of the same hole.
Fix: This shouldn't happen — Fastener Suite deduplicates by face token before applying countersinks. If you're seeing it, ensure you're running v1.0.0 or later. If the issue persists, report it with the face selection details.
Heat-set standards show the same values for Voron and McMaster
The two standards do use different press-fit diameters for some sizes (notably M3). If both appear identical in the panel, the wrong standard may be selected in the dropdown — check the active selection.
Also check: Open heat_set_data.json (via the Config
file button) and verify the Voron and McMaster rows for your size have distinct
values. The Voron M3 press-fit diameter differs from the McMaster M3 value.
Ready to streamline your fastener workflow?
Free and open source. Works on Windows and macOS. Full timeline editing. No subscription required.