V-groove pulley, customizable: any diameter, belt and shaft

A pulley for round belts, such as polyurethane or O-ring style belts, with a hub and an M3 set screw to hold it on the shaft. At the defaults it is 40 mm across and 22 mm tall: a 12 mm wide grooved wheel for a 4 mm belt and an 18 mm hub on a 5 mm shaft. Set the outer diameter (30 to 100 mm), the belt (2 to 6 mm), the shaft (3 to 8 mm), the bore clearance and the V angle (60 to 100 degrees).

Customize Change it with AIFree STL, 3MF and STEP, no accountMeasured on the model

Parameters

Outer diametermm

Round belt diametermm

Shaft diametermm

Bore clearancemm

Pulley width (groove part)mm

V angle (90 prints without support)deg

Hub diametermm

Hub length above pulleymm

M3 nut slot for set screw (off = tapped pilot)

Sliders and downloads are free. Changes by the AI designer use credits like any design; new accounts start with free ones.

It prints flat with the wheel on the bed and the hub up, with no supports at the default 90 degree V; below about 80 degrees the upper flank may need support. The groove is a plain V, and the belt rests on both flanks a little over 1 mm below the rim. Measure your belt and shaft before printing, and print one to check the 0.15 mm bore clearance and the nut slot.

Parameters

Every slider in the viewer above, with the range the model accepts. The model rebuilds valid at both ends of each range.

Parameter	Range	Default	What it changes
Outer diameter	30 to 100 mm	40 mm	Outside diameter of the wheel at the rim.
Round belt diameter	2 to 6 mm	4 mm	Diameter of your round belt. The groove is sized so the belt rests on both flanks a little below the rim.
Shaft diameter	3 to 8 mm	5 mm	Diameter of the shaft the pulley mounts on.
Bore clearance	0 to 0.4 mm	0.15 mm	Clearance added to the bore. Raise it if the pulley will not slide onto the shaft, lower it if it wobbles.
Pulley width (groove part)	8 to 25 mm	12 mm	Width of the grooved wheel. It grows automatically if the groove would leave rims under 1.5 mm thick.
V angle (90 prints without support)	60 to 100 deg	90 deg	Included angle of the V. 90 degrees prints without support; below about 80 degrees the upper flank may need support.
Hub diameter	16 to 30 mm	18 mm	Outside diameter of the hub that carries the set screw. With the nut slot on, it grows when needed to keep 1.6 mm of wall outside the nut.
Hub length above pulley	9 to 25 mm	10 mm	How far the hub stands above the wheel. The set screw sits halfway up it.
M3 nut slot for set screw (off = tapped pilot)	On or off	On	On: a 3.4 mm hole and a slot from the top of the hub for an M3 nut. Off: a 2.6 mm pilot hole for a self-tapping M3 screw instead.

Proof: measured on the model

What the design must satisfy and what our CAD engine measured on the model at the default values. Only measured values are shown here; nothing on this page has been printed by us yet.

Requirement	Wanted	Measured
Outer diameter at the rim	40 mm (the slider)	40 mm
Shaft bore	5.15 mm (5 mm shaft + 0.15 mm clearance)	5.15 mm
Diameter at the bottom of the V	31.7 mm (groove 4.2 mm deep)	31.66 mm
M3 set screw hole through the hub wall	3.4 mm, with an M3 nut slot	3.4 mm
Nut slot thickness, along the screw	2.8 mm (2.4 mm M3 nut + 0.4 mm play)	2.8 mm
Hub wall outside the nut, which the screw pulls the nut against	2 mm (at least 1.6 mm)	2.025 mm

valid solid, one body, 40 x 40 x 22 mm, fits a 256 x 256 x 256 mm printer; overhangs: 4.4% of surface would need support.

Print notes

Orientation: Flat, as modelled: the grooved wheel on the bed and the hub pointing up.
Supports: None at the default 90 degree V
Material: PLA or PETG
Layer height: 0.2 mm
Hardware: 1 x M3 set screw (grub screw); 1 x M3 nut (with the nut slot on)
Time and filament: About 25 min and 8 g at the default size: a rough estimate from the model's volume and surface (PLA, 15% infill, about 1 mm of walls, 0.2 mm layers), not a slicer.

Measure your belt and shaft with calipers before printing, then print one pulley to check the bore and the nut slot.
Drop the M3 nut into its slot from the top of the hub, flat side down, then thread the set screw in from the outside, through the nut, until it presses on the shaft.
Tightening the screw pulls the nut against the hub wall outside it. If you would rather not use a nut, switch the slot off and use a self-tapping M3 screw in the 2.6 mm pilot hole.
Below a V angle of about 80 degrees, check the preview for overhangs and turn on supports if needed.

How it was designed

Designed with buildcad's AI agent, checked by the buildcad team. This is the request it started from and an edited account of what it did (more on how text to CAD works).

The request
A V-groove pulley for a 4 mm round belt, 40 mm diameter, on a 5 mm shaft with an M3 set screw.

1
It sized the groove from the belt
The agent put the belt's centre 1.2 mm (0.3 x the belt) below the 40 mm rim and made the groove flanks touch a 4.2 mm circle, the belt plus 0.1 mm of play all round. It added an 18 mm hub with an M3 set screw and nut slot, and wrote checks for the 40 mm diameter, one 5.15 mm bore (5 mm plus 0.15 mm clearance) and one 3.4 mm set screw hole.
2
First build: a 40 degree V needed support
Its first groove was a 40 degree V. The model built, every check passed and the sweep rebuilt all 16 slider extremes, but the overhang check failed: 14.2% of the surface (836 mm2) would need support, because a narrow V leaves its upper flank nearly flat.
3
It opened the V to 90 degrees
With a 90 degree V, the area flagged for support dropped to 4.9% of the surface (258 mm2) and the overhang check passed. All 4 checks and all 16 slider extremes passed again.
4
What it left to the maker
Its reply asks you to measure the real belt and shaft, raise the bore clearance if the shaft is tight, and test-print the nut slot.
5
Our change
The run's nut slot opened to the outside of the hub, in line with the set screw, so tightening the screw would pull the nut out. We made the slot drop in from the top of the hub, 2.8 mm thick (a 2.4 mm M3 nut plus 0.4 mm play) with hub wall on both sides of the nut, and made the hub grow when needed to keep 1.6 mm of wall outside the nut. Nothing changes at the defaults except the slot.

One run of the agent: 1 min 21 s, about $0.17 of model time at list price (claude-sonnet-5-5). We changed the code afterwards, as described in the last step.

Change it with AI

Set the sliders, then press Change it with AI: a copy goes to your designs at those sizes and the designer opens with a suggested change you can edit. Its changes use credits like any design; new accounts start with free ones.

Change it with AI Describe your own part Use it from your own AI (MCP)