U‑Groove Nylon Bearing Roller 5x21mm 8Pcs Low Noise Sliding Pulley for Door Window Furniture Automation Equipment

Product DescriptionPremium U-groove nylon bearing rollers, 5mm bore, 21mm outer diameter, 7mm groove width, 8 pieces per set. Made of high-strength nylon shell and stainless steel bearing, wear-resistant, quiet, smooth rotating, rust-proof and durable. Perfect replacement for sliding doors, windows, shower doors, furniture casters and industrial automation guide pulley systems. Easy to install with no extra tools needed, stable operation without jamming or abnormal noise for long-term daily and industrial use.二、Twist Drill Correct UsageSelect Matching Drill BitChoose a suitable twist drill according to material and hole size. Confirm the drill bit is sharp, no rust, crack or bending deformation.Fix Workpiece FirmlyClamp the workpiece tightly to prevent shaking or offset during drilling, which avoids hole deviation and bit breakage.Adjust Speed AppropriatelyLow speed for hard materials such as metal, iron and steel; medium-high speed for wood, plastic and aluminum alloy. Do not over-speed operation.Vertical DrillingKeep the drill vertical to the workpiece surface. Start drilling slowly with low pressure to prevent slipping and scratching.Control Drilling PressureApply uniform and gentle pressure. Do not force pressing, which will cause overheating, bit burning or broken drill.Heat Dissipation & LubricationUse cooling oil or cutting fluid when drilling metal to reduce high temperature, extend drill bit life and ensure smooth holes.Exit SlowlyReduce speed and pull out the drill bit slowly after drilling through the hole to avoid edge collapse and workpiece damage.Post-use MaintenanceClean chips and dust, wipe dry and store properly to keep the drill bit sharp for repeated use.