Metal shoulder washer?
This precision shoulder bushing or cylindrical shoulder washer fits between a bolt or shaft and a mating surface. Its geometry includes a central hole and raised collar (the "shoulder") above the mounting surface. The collar lifts the bearing face to carry the strain, while the hole properly feeds the fastener or shaft through the assembly.
They use Metal Shoulder Washers when engineers design:
- Load distribution: The full-face shoulder spreads clamping force across a larger area than a flat washer, reducing surface stress on soft substrates.
- Robotic joints and precision actuator assemblies use pilot diameters to centre shafts, pins, or pivots.
- Electrical isolation: Aluminium or brass shoulder washers prevent galvanic corrosion in mixed-material joints by preventing dissimilar metals from conducting.
- Controlled spacing: Shank length replaces shims or poorly toleranced spacers to predict component gaps.
Metal Shoulder Washer Surface Finishes
Surface treatment extends shoulder washer life in demanding environments beyond the base material:
Aluminium washer anodising (Type II / Type III hardcoat): Clear, black, and bespoke colours. Surface hardness and wear resistance increase with hardcoat anodising.
Passivation: Standard for stainless steel-removes free iron and restores corrosion resistance following CNC machining. Steel washers used outdoors or in corrosive environments are protected by zinc or nickel plating.
Electroless nickel: Ideal for precision components requiring post-finish dimensional accuracy due to uniform coating thickness on complex geometries.
Plain / as-machined: Only dimensional precision is needed; customer handles surface treatment.
Engineers needed Metal Shoulder Washers
Every millimetre of clearance and gramme of contact surface matters in mechanical assemblies. Flat washers, sleeves, and shims cannot solve multiple technical concerns like the Metal Shoulder Washer.
1. Mating surfaces load evenly.
Compressive stress is concentrated beneath the bolt head or nut when a bolted joint clamps two surfaces. Normal flat washers' poorly controlled bearing surfaces convey this load. A consistent bearing circle is maintained by a metal shoulder washer with a shoulder diameter and face flatness of +/-0.01 mm. This avoids surface deformation, ensures clamp force consistency, and stiffens robotic arm joints, which reduce positional accuracy due to joint flex.
2. Clear Pilot and Alignment Directions
Inner bores of Metal Shoulder Washers are machined to precise tolerances (h6, H6, or custom fit). This collar precisely locates shafts, dowel pins, and shoulder bolts. Multi-axis assemblies like gimbals, camera rigs, CNC fixture plates, and medical device mechanisms benefit from self-centering because a few microns of misalignment reduce performance or premature wear.
3. Controlled stack spacing and height
Standard production shoulder washer shank lengths are +/-0.02 mm, precision grades tighter. Engineers place stacked assemblies correctly with this shank. Multiple flat washers can comply or rattle under vibration due to stacking faults, assembly flaws, and additional contact interfaces.
4. Electrically isolating mixed-material joints
In moisture or electrolyte, aluminium and steel fasteners galvanically corrode. An aluminium, brass, or dielectric-coated steel shoulder washer between incompatible metals prevents galvanic action. This is required for most marine electronics enclosures, battery management systems, and outside lights.
Standard Sizes and Tolerances
KEY-CNC machines Metal Shoulder Washers to your exact specifications. Below are common size ranges and achievable tolerances for reference. Custom sizes outside these ranges are available on request.
|
Parameter |
Standard Range |
Precision Grade |
|
Inner Bore (ID) |
3 mm - 50 mm |
+/-0.01 mm |
|
Outer Diameter (OD) |
6 mm - 80 mm |
+/-0.015 mm |
|
Shoulder Height |
2 mm - 25 mm |
+/-0.02 mm |
|
Total Length |
3 mm - 30 mm |
+/-0.02 mm |
|
Face Flatness |
<=0.02 mm |
<=0.005 mm |
|
1.6 - 3.2 um |
<=0.8 um |
FAQ
Q: What is the difference between flat washers and shoulder washers?
A: Load distribution on flat washer limited by hardness and thickness. The cylindrical "shoulder" collar of the metal shoulder washers establishes the bearing face and ensures proper pilot diameter for alignment. It can also be machined to closer tolerances on shank length and bore diameter. Shoulder washers are better than flat washers for precision assemblies.
Q: Will Key-CNC make custom bores or shoulders?
A: CNC machining can make Metal Shoulder Washers with non-standard inner bore, outer diameter and shoulder height ratios, oversized shoulders and stepped bores. Once we have your drawings or CAD model, our technical staff will confirm manufacturability and offer the most cost effective option.
Q: What is the minimum order for custom metal shoulder washers?
A: Order a prototype. Our manufacturers do custom work in high volume and low MOQ. Volume price available on orders of greater than 500 pieces if required by geometry. Dedicated tooling or jigging available.
Q: Top outdoor surface coatings?
A: Aluminium washers for outdoor and marine use are protected with hardcoat anodized (Type III) or passivated 316L stainless steel, 25-50 um alumina. They withstand UV, salt spray, and moisture. We can help with selection of area finish with our expertise.
Q: What file types do you accept for custom orders?
A: 3D Models: STEP, IGES, Parasolid 2D Drawings: PDF, DWG, DXF Catalogue items, drawings or part numbers for standard products. Ask for the design-friendly format.
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