Open-Ended Timing Belts

What an Open-Ended Belt Is

An open-ended timing belt is supplied as a continuous roll with teeth on the inside face, cut to whatever length the application needs. Unlike endless belts (molded loops), an open-ended belt is installed under tension and anchored at both ends — the classic arrangement for linear drives where the belt moves a carriage along a fixed axis.

Open-ended belts are the standard for:

• Linear actuators and positioning stages
• 3D printer X/Y axes
• CNC router and laser cutter gantries
• Belt-driven slides and pick-and-place arms
• Custom-length runs where no standard endless belt fits

How to Measure the Length You Need

For a linear drive with the belt anchored at both ends and wrapped around a pulley:

1. Measure the travel: the distance the carriage needs to move (stroke).
2. Add the pulley wrap: each pulley engages roughly half its circumference of belt (for a 20-tooth GT2 pulley, about 20 mm of wrap per pulley).
3. Add the anchor allowance: material clamped or welded at each end.
4. Add tensioner travel: the adjustment range you need for tensioning.

Order a little longer than your calculation — an open-ended belt can always be cut shorter, but it cannot be stretched.

Choosing the Width

Width carries the load. Light printer axes run 6 mm GT2; heavier gantries step up to 9-10 mm; industrial actuators run 15-25 mm HTD 5M. As a rule, double the width roughly doubles the load capacity. If the carriage mass is uncertain, size up — belt cost scales slowly with width, and an under-width belt stretches or skips.

Cutting and Finishing

• Cut square: a square end seats better in clamps and welds cleaner. Mark with a square and cut with a sharp blade or belt cutter.
• Seal the cut end: in high-flex or high-speed service, seal the cut edge (heat or adhesive) to prevent fraying and cord pull-out.
• Leave margin: never cut a belt to exactly zero clearance — you need room for the tensioner.

Joining Options

Clamps (Field-Friendly)

Clamps grip the belt mechanically and suit quick replacement and prototyping. They add a small lump to the belt, which matters at high speed or on small pulleys. Use two clamps per anchor point for a symmetric grip.

Welding (Stronger, Factory-Done)

Open-ended belts can be welded into endless loops. A welded joint is nearly as strong as the parent belt and runs smooth over pulleys. Welding is done at the factory — the belt material and tooth pitch must match the weld tooling.

Screw/Plate Anchors (Structural)

For fixed anchors at the carriage ends, a plate-and-screw anchor clamps the belt between two plates. This is the standard arrangement on CNC and printer axes.

Tensioning an Open-Ended Belt

Anchor one end, route the belt over the pulley(s), anchor the other end with the tensioner at its loosest, then take up tension until the belt deflects about 1-1.5% of the free span length at mid-span. Re-check after the first day of running — new belts seat and may need a small re-tension.

Too loose: the belt skips under load and the carriage loses position. Too tight: the bearings and motor shaft carry extra load, and the belt stretches permanently.

Common Pitfalls

• Wrong pitch: a GT2 pulley needs a 2 mm pitch belt — nothing else fits. Measure tooth pitch before ordering.
• Measuring between pulley centers instead of around the wrap: add the wrap and anchors, or the belt comes up short.
• Cutting to exact length with no tensioner range: you need adjustment room.
• Mixing widths: the belt must match the pulley face width and the carriage anchor width.
• Buying a roll that is too narrow for the load: stretch and skip follow quickly.

Sizes We Stock

Belt	Pitch	Common Widths	Typical Use
GT2 / 2GT	2 mm	6, 9, 10 mm	3D printers, light CNC
GT3	3 mm	6, 9, 10 mm	Heavier printer gantries
HTD 5M	5 mm	6, 9, 15, 20, 25, 30 mm	Actuators, light industrial
HTD 8M	8 mm	9, 15, 20, 30, 50 mm	General linear drives

Open-ended stock is sold per meter. Tell us the pitch, width, and length — or the application — and we will cut to your spec.

Related Guides

• HTD 5M Timing Belts
• GT2 Timing Belts
• Timing Belt Tension Guide [Browse GT2 Belts] [Browse HTD 5M Belts] [Timing Belt Tension Guide] [Request a Quote]