Arc R Nylon Plastic Pulley Wheel 604ZZ Deep Groove Ball Bearing 4x16x6mm POM

The Arc R (round-bottom) groove is designed for round belts, O-rings, and round cord — typically 2–4 mm diameter. It is not intended for flat GT2/GT3 timing belts, which require a flat or tooth-profile groove. If you are running a toothed belt, please check our GT2 pulley listings instead.

The 604ZZ bearing has a 4 mm inner bore, so you need an M4 shoulder bolt, M4 screw, or a 4 mm smooth shaft as the axle. The shoulder or smooth section must be at least 6 mm long to span the full bearing width. Standard M4 × 10 mm or M4 × 12 mm shoulder bolts work well in most 3D printer and CNC frames.

POM has low moisture absorption (typically <0.2%) and good dimensional stability in humid conditions, making it more suitable for damp environments than nylon (PA6/PA66). However, prolonged UV exposure can cause surface degradation. For outdoor applications, consider adding UV protection or shielding the pulley from direct sunlight.

The 604ZZ bearing has a dynamic load rating of approximately 1.0–1.5 kN and a static load rating of approximately 0.5–0.7 kN (values vary by bearing grade). For typical 3D printer belt tension and light CNC tensioner duty, these wheels are well within their rated capacity. They are not intended for heavy industrial conveyor loads.

The 604ZZ bearing is double-shielded and pre-greased at the factory, so no additional lubrication is required before installation. If you are operating in a very dusty environment or after extended use, you can add a small amount of light machine oil or bearing grease through the shield gap to extend service life.

Choose the 1-piece pack if you need a single replacement for a worn idler. The 4-piece pack covers a full CoreXY or Cartesian printer rebuild (typically 2–4 idler positions). The 10-piece pack is ideal for workshop stock, group builds, or if you are building multiple machines and want spares on hand at a lower per-unit cost.

These 604ZZ-based pulley wheels are compatible with any printer frame that uses M4 axle bolts and a round-groove idler position. Many Voron, Ender 3 series, and custom CoreXY builds use this bearing size for non-toothed idler positions. Always verify your frame's BOM (bill of materials) to confirm the required bearing model and groove profile before ordering.