Electric vehicle drivetrains produce torque instantly and repeatably, which is good for performance and hard on the parts that transfer and manage motion. Friction shims – thin, precise parts that control clamping force, position, and wear between components – are among the parts getting more scrutiny as EV torque grows. This article looks at why electric powertrains lean on friction shims, what the parts actually have to do, and how they are manufactured to hold repeatable performance.
What Friction Shims Do
A shim is a thin part used to fill a gap, set a position, or manage load between components. A friction shim adds a controlled friction or wear behavior: it can maintain a preload, damp motion, transfer torque through a friction interface, or protect a mating surface. In drivetrains, shims set bearing preload, limit end play, and manage axial loads.
The requirement is usually a controlled thickness, hardness, surface finish, and material behavior, and those have to hold across large quantities.
Why EV Torque Changes the Demand
Electric motors deliver high torque from low speed and do it with rapid, repeated load changes. That profile stresses the joints and bearings where shims sit, and it makes the shim’s tolerance and finish matter more. The parts also operate in systems with less noise masking, so motion control and consistency become audible and measurable requirements.
The result is not necessarily a surge in shim volume per se in all cases; it is a shift toward more precisely specified, thinner, harder shims produced at scale with tight control.
Materials for Friction Shims
Shim materials balance strength, wear, friction behavior, and thickness control. Spring steel and hardened carbon steel provide stiffness and load capacity; stainless and specialty alloys add corrosion resistance; some designs use coated or laminated materials for friction tuning. The material choice follows the load, environment, and friction requirement – not a generic “steel” callout.
Machining Shims to Specification
Thin shims are demanding to machine. They need flatness, parallel faces, controlled thickness, clean edges, and burr-free surfaces. Lapping, grinding, and precision machining produce the flat, parallel, dimensionally stable shims these applications need, and secondary operations such as deburring, hardening, or coating follow. Thickness control measured at the micrometer and micrometre level is the core of the operation.
Quality and Documentation
Because shims control critical gaps and loads, material and dimension documentation matters. Confirm material grade, hardening and heat treatment, surface finish, thickness measurement method, and any lot traceability the application needs. The drawing should name which surfaces are functional and the inspection point.
Scaling to Volume
The volume question is where manufacturing road routes diverge. At prototype or low volume, precision machining gives control and flexibility. At high volume, processing should move toward an efficient route – often stamped or lapped and ground – but always with the same thickness, flatness, and surface control. Confirm the route against the part’s critical features before volume cancels the prototype’s discipline.
The Bottom Line
EV torque puts demanding requirements on the thin parts that manage load, and friction shims are a good example: controlled thickness, flatness, finish, and friction behavior, produced at scale. Whether they are machined, ground, or stamped, the part has to hold a specification, not just a drawing. If EV drivetrains keep raising torque and consistency demands, expect more precision, more documentation, and more capability on these small parts – and choose the manufacturing route that delivers the specification.
Note: shim designs, friction requirements, and manufacturing routes vary by application; confirm material, heat treatment, and measurement against the application and drawing.