20-Tooth GT2 Aluminum Idler Pulley - 5mm Bore Bearing for 6mm Belts

Specifications

• Tooth Profile: GT2 (Rounded)

• Tooth Count: 20 Teeth (20T)

• Type: Passive Idler (Free-spinning)

• Inner Bore Diameter (Bearing): 5mm

• Belt Width Compatibility: 6mm

• Material: Aluminum Alloy (Shell) / Steel (Bearing)

• Fixing Mechanism: None (Slides onto 5mm shaft/bolt)

Key Applications and Projects

• 3D Printer Belt Tensioners: Mounting this pulley onto a sliding 3D-printed bracket at the far end of the X or Y axis to pull the timing belt taut.

• CoreXY Gantry Routing: Serving as the crucial corner pivot points where the complex, crossed belt paths of a CoreXY machine must change direction smoothly.

• Automated Camera Sliders: Providing a low-friction return pulley at the far end of a meter-long aluminum extrusion slider track.

Unlock New Capabilities (Project Evolution)

• The Perfect CoreXY Upgrade: If you are building a custom CoreXY machine (like a Voron), utilizing smooth bearings where the belt teeth contact the pulley is a recipe for poor print quality. Evolve your build! By swapping out your smooth 625ZZ corner bearings for these 20T Toothed Idlers, your belt teeth will mesh perfectly through the corners. This immediately eliminates "chatter," vastly extends the lifespan of your belts, and results in flawlessly smooth exterior walls on your 3D prints!

Package Includes:

• 1 x 20-Tooth GT2 Aluminum Passive Idler Pulley (with 5mm Internal Bearing)

FREQUENTLY ASKED QUESTIONS (FAQ)

1. What does "GT2" mean? "GT2" stands for "Gates Tooth 2mm." It describes the rounded profile of the teeth and the exact 2mm distance (pitch) between the center of each tooth.

2. What is an "idler" pulley? An idler pulley does not drive the belt; it simply guides it, redirects it, or applies tension to it. It spins freely on a shaft rather than turning the shaft.

3. What is the difference between a drive pulley and an idler pulley? A drive pulley has a solid metal hub with set screws to lock onto a spinning motor shaft. An idler pulley has internal ball bearings so it can spin freely on a static bolt.

4. Why use a toothed idler instead of a smooth one? If the flat back of your belt touches the pulley, use a smooth idler. If the toothed side of your belt touches the pulley, use a toothed idler. This prevents the rubber teeth from being crushed and causing vibration.

5. What size bolt does this fit? The internal bearing has a 5mm bore. It perfectly fits a standard M5 metric machine screw or a 5mm smooth steel rod.

6. How many teeth does this pulley have? It has exactly 20 teeth.

7. What width of timing belt should I use? The toothed area is specifically designed to accommodate standard 6mm wide GT2 timing belts.

8. Does it come with set screws? No. Because it is a free-spinning idler with a bearing, it does not use or need set screws.

9. What does the word "Perlin" mean in the title? This is a common translation artifact from overseas manufacturing. In this context, it simply means "Bearing" (referring to the internal ball bearing).

10. Can I mount this directly to my stepper motor? No. Stepper motors spin and require a drive pulley to transmit that power. If you put this on a motor, the motor shaft will just spin inside the bearing, and the belt won't move.

11. How do I tension a belt with this? You mount the M5 bolt holding this pulley onto a slotted bracket. You pull the bracket away from the motor to tighten the belt, and then tighten the bracket down to the machine frame.

12. Are the internal bearings pre-lubricated? Yes, the small internal bearings are packed with grease at the factory and do not require maintenance.

13. Can the bearing be replaced if it goes bad? While technically possible to press the tiny bearing out of the aluminum shell, it is almost always cheaper and easier to just buy a new idler pulley.

14. Will the belt slide off the top or bottom? No, the pulley features two flared outer flanges specifically designed to keep the 6mm belt tracked perfectly in the center.

15. Can I use this with a T2.5 belt? No. T2.5 belts have a square tooth profile and a 2.5mm pitch. They will not mesh smoothly with this GT2 pulley.

16. Does using a 20T idler instead of a 16T idler change my machine's gear ratio? No. Because an idler does not drive the belt, its size has absolutely zero effect on the "steps per mm" or travel speed of your machine.

17. What material is this made of? The outer toothed shell and flanges are machined from aluminum alloy, while the central bearing is made of steel.

18. Why does my belt make a clicking sound when passing over this pulley? Clicking usually means the belt is far too tight, the pulley is mounted crooked (causing the belt to rub hard against the flanges), or you are using a mismatched belt pitch (like T2.5).

19. Can I use this on the Z-axis of my printer? While you can, Z-axis synchronization belts usually form a closed loop around the top of the machine where only the smooth back of the belt touches the tensioner. In that case, a smooth idler is actually better.

20. Does it matter which way it faces when I install it? No, the pulley is completely symmetrical top-to-bottom. You can install it in either orientation.