Knurling

Diamond patterns.
Grip surface.
Integrated with turning.

Knurling creates repeating surface patterns — typically diamond, straight, or helical — for grip, press-fit interference, or decorative effect. Applied during CNC turning operations. Fast, precise, and consistent across production quantities.

Knurling Quote CNC turning

Diamond / straight DIN 82 Press fit interference CNC integrated

01 · What it is

How Knurling works.

Knurling is a machining process that creates a textured pattern on cylindrical surfaces by pressing hardened knurl wheels into the workpiece. Two knurl wheels with reverse helical patterns produce a diamond pattern; a single straight-patterned wheel produces straight knurls; single helical wheels produce helical patterns. The pressure displaces material (cold working) rather than cutting — the raised pattern is formed by material flow, not removal.

Three primary functional purposes: grip (knurled tool handles, knobs, adjustment screws — provide finger grip), press-fit interference (knurled shafts provide bite when press-fit into smooth holes, creating a rotational lock), and decorative (visual pattern on cosmetic parts like knobs, levers, premium hardware).

DIN 82 specifies knurl pattern types and pitches: RAA (right-hand helical), RBL (left-hand helical), RGV (rectangular straight), and diamond variants. Common pitches 0.5–1.5 mm. CNC-integrated knurling means the pattern forms during lathe production without secondary operation — fast and cost-effective at volume.

02 · Specifications

Capability specs.

DIN 82

Standard

Standard specification for knurl patterns and pitches

0.5–1.5 mm

Pitch range

Standard knurl pitch range. Fine (0.5), medium (0.8), coarse (1.2–1.5)

Diamond / straight / helical

Pattern options

Three primary pattern families. Custom patterns via tool selection

CNC integrated

Process

Applied during CNC turning in production run — no secondary operation

Press fit

Interference use

Knurled shaft pressed into smooth hole creates rotational lock

Cold formed

Material effect

No material removal — surface displaced, slightly work-hardened

±0.1 mm

Pattern depth

Knurl depth tolerance — typical for production knurling

Any ductile metal

Compatibility

Steel, stainless, aluminum, brass, copper — ductile metals cold-form well

03 · Applications

Where Knurling excels.

Tool handles

Manual tools requiring grip — wrenches, screwdrivers, knobs

Adjustment knobs

Rotary adjustment controls — thumbscrews, fine adjusters, lab equipment

Press-fit shafts

Shafts knurled where press-fit into plastic or soft metal housings

Manual operating controls

Industrial machine controls requiring tactile grip

Valve handles

Precision valve handles where finger grip matters

Specialty fasteners

Knurled thumbscrews, captive panel fasteners, specialty hardware

Premium hardware

Cosmetic knurled hardware for high-end products

Instrument controls

Test equipment knobs, scientific instrument controls

Medical device controls

Medical device adjustment knobs requiring grip even with gloves

04 · When not to use it

Not suitable for:

Every process has its limits. Being honest about where Knurling isn\'t the right answer saves time and money.

Cosmetic surfaces requiring smooth appearance
Parts that will be plated with thin coating (knurls may show through)
Very small diameters (below 3 mm) — tooling limitations
Brittle materials that crack rather than deform plastically
Applications requiring consistent seal against O-rings (knurl disrupts seal)

FAQ

Knurling questions.

Diamond: most common, maximum grip in all directions. Use for hand-operated knobs, handles. Straight: axial grip, prevents rotation. Use for press-fit shafts into plastic housings. Helical: single-direction grip, used for specific rotational direction requirements. Rule of thumb: for grip, diamond. For interference, straight or diamond depending on load direction.

Knurled shaft OD is slightly larger than the mating hole ID. When pressed in, the peaks of the knurl pattern bite into the hole material, creating a rotational lock. Typical design: shaft knurled to OD 0.05–0.15 mm larger than hole ID. For soft housings (plastic, aluminum), smaller interference. For hard housings (steel), larger. Proven technique for attaching shafts to plastic gears and knobs.

Specify base shaft OD (before knurling), knurl pitch and pattern, and target post-knurl OD. Example: "Shaft Ø10.0, knurled RAA 0.8, final Ø10.15 +0.05/-0.00." Material is displaced upward during knurling, so final OD is larger than base OD. We calculate knurl depth to achieve target final OD based on material properties.

Knurling adds minimal cost when integrated with CNC turning production. Typical: $0.50–2 added per part at production volume. Knurl tooling is inexpensive ($50–200 per knurl wheel set), amortizes across many jobs. For low-volume parts (under 50 pieces), setup cost may add $30–100 total. For high-volume production, knurling is negligible cost.

Yes — knurled plastic parts common for knobs and handles. Process varies: molded-in knurl pattern during injection (most common for production), or machined knurl on turned plastic parts. Delrin and nylon knurl well on lathe. ABS and PC are more challenging — may require higher speeds or different tooling approach.

In-line (on lathe during turning): preferred — no extra setup, no handling between operations, consistent positioning. Standard for production. Secondary operation: only used for parts requiring knurl on features not accessible during primary turning. Rare — usually designed out of the process.