CNC Turned and Milled Aluminum Timing Belt Pulley
6061-T6 aluminium timing belt pulleys turned and hobbed with HTD 3M, 5M and 8M profiles, bores held to H7 with runout under 0.02 mm, integral or pressed flanges and lightening holes balanced around the hub. Tooth count, pitch and flange style are built to the belt the pulley has to drive.
- Tooth Profile Cut In
- Bore and Keyway to H7
- Radial Runout 0.02 mm
- Balanced Lightening Holes
*Send the belt part number and the shaft fit, not just a pulley diameter. Pitch diameter, tooth depth and flange clearance all come from the belt, and a pulley that is 0.1 mm off pitch will climb the belt under load.
Timing Belt Pulley Overview
A pulley is a gear with a belt instead of a mate. Its pitch diameter sets the ratio, its tooth profile decides how evenly the load is shared, and its runout decides whether the belt tracks or walks off the flange.
The body is turned first, the bore is finished and the pulley is mounted on a mandrel between centres, and only then are the teeth hobbed. Cutting teeth before the bore is finished is the usual reason a pulley runs out and eats one edge of the belt.
6061-T6 Aluminium Bar
6061-T6 is light, machines cleanly and anodizes thin enough that the tooth profile stays inside tolerance. It is the default for pulleys up to about 200 mm where the drive is not overloaded.
7075-T6 or Steel for High Torque
7075-T6 is used when the pulley is small and the torque is high, since the teeth resist shearing. Steel is specified for drives above roughly 30 Nm where an aluminium tooth would wear into a hook shape.
Torque and duty cycle decide the material; belt speed decides the balance class. A light pulley that is out of balance is worse than a heavy one that is true.
Timing Belt Pulley Specifications
Turning and hobbing data for aluminium pulleys, with the tooth, bore and runout values that decide whether the belt runs true.
| Specification | Machining Data | Specification | Machining Data |
|---|---|---|---|
| Product | Timing Belt Pulley / HTD Pulley | Machining Process | CNC Turning, Gear Hobbing, Milling |
| Material | 6061-T6 Aluminium Bar | Tooth Profile | HTD 3M / 5M / 8M, GT2, T2.5 – T10 |
| Outside Diameter | 15 – 220 mm | Tooth Count | 12 – 120 Teeth |
| Bore Diameter | 5 – 45 mm, H7 | Bore Runout | 0.02 mm |
| Pitch Tolerance | ±0.02 mm on Pitch Diameter | Face Runout | 0.02 mm |
| Flange Thickness | 2 – 4 mm, Pressed or Integral | Surface Finish | Ra 1.6 µm Flanks, Ra 3.2 µm Body |
| Customization | Keyway, Set Screws, Lightening Holes, Taper Lock Bore | Lead Time | 4 – 6 Days Sample, 10 – 14 Days Batch |
| Inspection | Tooth Profile Projector, Bore Plug Gauge, Runout on Centres | Packing | Foam Dividers, Individually Bagged, Carton |
Key Features of Our Timing Pulleys
Teeth cut on the finished bore, flanges that clear the belt.
Teeth Cut After Boring
The pulley is hobbed on a mandrel that is dialled to the finished bore, so the tooth circle is concentric to the shaft and the belt does not walk to one flange.
Tooth Profile Checked on a Projector
A sample from each run is checked against the belt profile on an optical projector, which catches a worn hob before a whole batch is cut off pitch.
Flanges Squared to the Teeth
Pressed flanges are checked for squareness and integral flanges are turned with the tooth blank, so the belt sits against a true face rather than a burr.
Lightening Holes Balanced
Holes are placed symmetrically and the pulley is checked for static balance above 3,000 rpm, which removes the vibration that shows up as belt flutter.
Pulley that has to hold pitch under load?
Surface Finishes for Timing Pulleys
Coating thickness on a tooth flank changes the pitch line, so the finish is chosen before the tooth is cut.
| Finish | Main Purpose | Finish | Main Purpose |
|---|---|---|---|
| Clear Anodizing | Corrosion protection that keeps the tooth profile in tolerance | Hard Anodizing | Wear resistance on high-cycle drives |
| Masked Bore | Keeps the shaft fit at H7 | Bead Blasting | Matte body before dye |
| Black Dye | Common machine-tool colour coding | Laser Marking | Tooth count and bore size on the hub face |
*Hard anodizing adds 25 to 50 µm, which is more than the tooth tolerance on a 3M profile. Hard anodized pulleys are cut with a corrected hob and the profile is re-checked after coating.
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Turning and Hobbing Process
Teeth are cut after the bore is finished, so the profile runs on the shaft axis instead of on the bar axis it happened to be turned from.
01. Belt and Shaft Review
Check the belt profile, pitch and width against the drawing, confirm the shaft fit and decide whether the flange is integral or pressed before the blank is cut.
02. Turn the Blank
Turn the outside diameter, both faces and the bore in one set-up, leaving stock on the tooth diameter and finishing the bore to H7 so it can be used as the hobbing datum.
03. Hob the Teeth
Mount the blank on a mandrel dialled to the bore, hob the tooth profile to the correct depth and check the first part on the projector before running the batch.
04. Mill Keyway and Holes
Cut the keyway, set screw flats and lightening holes with the pulley still on the mandrel, so every feature is referenced to the same axis as the teeth.
05. Anodize, Balance and Pack
Mask the bore, anodize, check runout and static balance, then bag each pulley with foam dividers so the teeth do not knock in transit.
Send the belt part number with the shaft fit, and we will quote the pulley with the tooth profile matched to the belt you actually run.
Timing Belt Pulley FAQs
Yes, if you send the belt part number. HTD, GT and T profiles differ in tooth depth and root radius, and a pulley cut to the wrong one will wear the belt within a few hundred hours.
0.02 mm radial and 0.02 mm face on a pulley up to 150 mm, measured on centres. Above that the blank is heavier and 0.03 mm is realistic.
Both. Integral flanges are turned with the blank and are stronger; pressed flanges are thinner and cheaper but must be checked for squareness before the pulley is balanced.
It is cut after hobbing with the pulley still on the hobbing mandrel, so the keyway is referenced to the tooth circle rather than to a marked line on the hub.
Yes, but the tooth is cut with a corrected hob and re-checked after coating, because 25 to 50 µm on a flank changes the pitch line on a small profile.
Four to six days for a sample including a new hob if the profile is standard, and ten to fourteen days for a batch. A custom profile needs a hob made first, which adds about two weeks.
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