Mirror Finish Dowel Pin with Ra 0.2 Polished Surface and Cylindricity 0.005mm for Precision CNC Turning Assemblies

A mirror pin that keeps its edge. Ra 0.2 achieved without rounding the chamfer you need.

• Surface roughness: Ra 0.2 µmMeasured along the axis, both directions.
• Cylindricity: 0.005 mmNot just diameter at three points.
• Order size: 1 piecePrototype in 3–7 working days.
• Quality & materialsISO 9001:2015 · SS304 / 316L / 420, hardened 440C · passivated after polishing · exporting since 2008.

A mirror pin looks like the simplest part in a catalogue and behaves like the most deceptive. The surface is easy to make shiny — a buffing wheel or a run of abrasive film will do it. What polishing also does is round the chamfer, soften the end face, and in the worst case barrel the diameter, so the pin that measures beautifully on a profile projector no longer seats in its hole the way it did when it was turned.

We get the finish from the cutting process first: a fine finishing pass with a sharp, small-nose insert at high surface speed and a light depth of cut, which produces Ra 0.4 directly off the tool. Where the drawing calls for better, the part goes to a controlled polish that protects the chamfer with a mask or a fixture, and the chamfer width and end-face flatness are re-measured afterwards, not assumed. Roughness is then checked along the axis and around the circumference, because a pin that is smooth one way and striped the other will wear its bore unevenly.

• Material: SS304, SS316L, SS420, SS440C (hardened), 17-4PH, brass C36000, aluminium 6061, PEEK and POM for non-marking pins.
• Forms: plain dowel pin, stepped pin, headed pin, grooved pin, taper pin, hollow pin, pin with cross hole, pin with thread at one end.
• Finish: as-turned Ra 0.4, polished Ra 0.2 or Ra 0.1, passivation, electropolish, hard chrome, DLC, PTFE coating.
• Tolerance class: g6, h6, h5, or a fit defined against your measured bore.
• Size: diameter 1 mm to 40 mm, length 3 mm to 300 mm.
• Input: STEP, IGES, DXF, PDF drawing, or a sample pin we measure and re-model.

A pin drawing is small but it carries a fit class, a hardness and often the bore it must match — enough to identify a mechanism. We sign a mutual NDA before any file is opened, in English or Chinese or on your own form, and return a countersigned copy before work starts. Access is limited to the project engineer, the lathe programmer and the cell supervisor, with the file in a restricted folder rather than the open shop network. The cell is camera free: no photographs for our catalogue or website, no customer part kept on display or reused as a sample, subcontracting only with your written approval, and at program close drawings and inspection data are deleted or returned with written confirmation.

Dongguan Changxinda Precision Technology Co., Ltd has machined custom metal parts since 2008: 15+ years, 90 to 100 staff, 50–60% of output exported to North America and Europe, 200+ customers served, turnover in the RMB 10–20 million band. The plant runs CNC lathes, turn-mill combined centres with live tooling and sub-spindle, and 4-axis / 5-axis machining centres under an ISO 9001:2015 quality system, serving medical, robotics, automotive, aerospace, automation, laser, LED, lithium battery and precision instrument programs. Turning, polishing, passivation coordination and roughness measurement are all in our own plant in Dongguan.

Turned pins and precision shafts from this plant ship into ten sectors. The list is what customers order, not a marketing wish-list.

All ten sectors run through the same plant and the same ISO 9001:2015 inspection discipline — only the material, finish and documentation package change.

• Prototype: 3–7 working days after drawing approval, including polishing and passivation.
• Small batch 100–1,000 pcs: 7–14 working days; polishing is the constraint, not turning.
• Repeat orders: released from archived program and polishing fixture — diameter and finish repeat to the same values.
• Capacity: 10,000 pieces per month across the plant.
• Visibility: a dated progress note with photos of your actual pins at turning, polishing and final measurement.
• Shipping: each pin in its own sleeve or bag, no pin-to-pin contact, foam-lined carton so a polished surface arrives as it left.
• Rush: weekly polishing and passivation slots held; tell us the deadline and we confirm before the order.