Shaft Collars

A shaft collar is a cylindrical clamp that fits around a shaft and holds an adjacent component in place. They locate bearings axially, act as positive stops for linear motion, space hubs on a shared shaft, and provide mounting points for sensors, levers and brackets. Compact and quick to install or remove, they do work that would otherwise need a machined shaft shoulder — with the advantage that a collar can be repositioned when the assembly changes.

Quick Reference — Collar Type by Application

Shaft Collar Types

Set-screw collars

Solid ring with one or two grub screws threaded radially through the wall. The set screw drives onto the shaft and grips by friction plus a small bite. Cheapest, smallest profile, installs in seconds. Suits soft or mild-steel shafts where a witness mark is fine. Cup-point gives the highest holding force; knurled cup-point bites harder again; flat-point is gentler but slips under shock.

One-piece clamp collars

Solid ring with a radial slit and a clamp bolt that draws the slit closed. The bore contracts uniformly around the shaft and holds by friction across the full bore. No witness mark, even clamping, higher holding torque than set-screw. The everyday choice for hardened or finished shafts, precision shafting and stepper-motor assemblies.

Two-piece clamp collars

Clamp collar split into two semi-circular halves joined by two bolts. The advantage is install access — wraps around the shaft from the side, no need to slide on from a shaft end. For retrofit where the shaft already carries bearings, pulleys and couplings, this is the only sensible answer. Costs more, routinely saves hours.

Heavy-duty clamp collars

Thicker wall, larger clamp bolts (typically higher-grade socket head cap screws), wider face. For heavy gearboxes, large sprockets under shock load, sliding doors and lift columns. Holding torque can be more than double a standard collar of the same bore.

Mountable and hub collars

Clamp collars with tapped holes or flats on the OD for attaching brackets, sensor mounts, lever arms or pointers. Common in conveyor, instrumentation, automation and bespoke machine builds.

Shaft locating collars

Precision-machined clamp collars with closer bore and face tolerances, used as a bearing seat reference or precision axial stop. Face squareness to the bore is the critical feature.

Set-Screw vs Clamp — Direct Comparison

Warning — set-screw collars on hardened shafts. If the shaft is case-hardened, induction-hardened or through-hardened above approximately 35 HRC, a set screw cannot bite and the collar will slip under load. Use a clamp collar. "Torquing it harder" snaps the set screw or strips the collar thread without improving grip.

Materials

• Mild steel zinc-plated or black-oxide — default workshop choice. Zinc for indoor use; black-oxide for non-reflective work.
• Stainless 304 and 316 — food, dairy, pharmaceutical, marine and washdown. 304 covers most corrosion; 316 adds chloride resistance for coastal work. Match clamp bolt material — a plated-steel bolt in a stainless collar will rust and gall the thread.
• Aluminium — lightweight, lower holding force. Instrumentation, light automation. Not for heavy loads.
• Specialty — brass for non-sparking; engineering plastic (acetal, nylon) for static-sensitive or non-conductive applications. Stocked to order.

Sizing — Bore, OD and Width

The critical dimension is the bore, which must match the shaft diameter. Clamp collars typically run a tight bore (H7 or ±0.05 mm) so the collar slides on freely but takes up cleanly when tightened. Set-screw collars run a looser bore (±0.10 mm or wider) because the set screw takes up the gap. Wider collar = higher holding force. Choose the smallest collar that meets the requirement and fits the envelope.

Metric collars (1 mm steps from 6 mm upward) are standard in Australia. Imperial (1/16" or 1/8" steps) is stocked for retrofit. Verify shaft size with vernier calipers — mixing metric and imperial is the most common ordering mistake on legacy gearboxes.

Selection Criteria

• Shaft diameter — measure with calipers; don't trust the drawing if the shaft has been ground or sleeved
• Shaft hardness — if hardened above ~35 HRC, clamp collar only
• Shaft surface finish — finished/precision shafts need a clamp collar to avoid marking
• Holding force / axial load — set-screw for light, clamp for medium-heavy, heavy-duty for shock and high-thrust
• Install access — two-piece clamp if you cannot slide a collar on from the shaft end
• Environment — stainless for corrosion; specialty for spark/static-sensitive
• Vibration — clamp preferred; if set-screw must be used, add thread-locker

Installation Best Practice

• Clean the shaft at the collar location — remove oil, grease, scale and burrs. Friction grip needs metal-to-metal contact.
• Set-screw collars — position, hold square, tighten the set screw to manufacturer torque. Alternate small increments on two-set-screw collars. Apply medium-strength thread-locker (Loctite 243 or equivalent) on vibrating shafts.
• Clamp collars — slide to position, square the face to the bearing or shoulder being located against, tighten the clamp bolt(s) to spec. Alternate small increments on two-bolt collars to draw the clamp evenly.
• Two-piece — fit the halves square to each other, tighten both bolts evenly to avoid cocking the clamp.
• Re-check after run-in — verify torque after the first hour. New collars sometimes seat slightly and lose pre-load.

Warning — do not over-torque clamp bolts. Going past the manufacturer's torque spec distorts the collar bore, reduces clamping uniformity, and can actually reduce holding force. If the collar slips at correct torque, the next size up or a heavy-duty version is the answer — not more torque.

Common Applications

• Bearing axial location — locking the inner ring against drift, replacing or supplementing a machined shoulder
• Motion stop / end-of-travel limit — physical stop for linear-bearing carriages, slides and shafted actuators
• Hub spacing — holding two sprockets, pulleys or gears at a fixed axial distance on a shared shaft
• Sensor and encoder mounting — mount point for proximity sensors, rotary encoders and pointers
• Conveyor and roller shafts — preventing rollers and tensioners drifting axially under load
• Retrofit axial location — adding a stop or spacer to an existing assembly without re-machining

Standards Reference

• DIN 705 — Adjusting rings (shaft collars), light series (Form A) and heavy series (Form B). Dimensions, tolerances and materials for set-screw style adjusting rings. [VERIFY:] current edition year.
• DIN 6315 — Set collars with cone-point set screw. Geometry of the set-screw style common in European-spec power transmission. [VERIFY:] current edition year.

Companion Components

• Couplings — shaft to shaft, where a collar often locates the coupling hub axially
• Taper-lock bushes — standard mount for sprockets, pulleys and timing pulleys
• Locking assemblies — keyless shaft-hub connections for higher torque than collar or taper-lock
• Key steel and key stocks — positive torque transfer where the collar handles axial location
• Sprockets, V-pulleys, timing pulleys — driven components a collar locates
• Bearings — bearings whose inner rings the collar holds against
• Grub screws — replacement set screws (cup-point preferred)
• Socket head cap screws — replacement clamp bolts

AIMS' Note on Shaft Collar Selection

If you are unsure which collar suits your application, four pieces of information let us recommend confidently:

1. Shaft diameter — measured, not assumed
2. Holding force — what the collar is restraining, steady or shock load
3. Install access — can a one-piece slide on from the shaft end, or is two-piece required
4. Environment — indoor dry, washdown, marine, food contact, hot

Send those details through to our team and we'll match the right collar from stock or source it for you.

Companion Resources

• Keyways, keys and key steel size charts — where the collar handles axial location and the key handles torque
• Taper-lock bush guide — for mounting pulleys and sprockets the collar then locates
• Shaft coupling guide — coupling types and hub axial location
• Flexible coupling guide — flexible types and shaft-end fitment

Locking Collars — Shaft Collar Synonym

Locking collars is an alternative trade name for clamp-style shaft collars — the one-piece or two-piece collars that lock onto a shaft by clamping action (rather than set-screw grip). The terms are used interchangeably across machinery datasheets, automation specifiers and conveyor OEMs. Where higher holding force, no shaft witness mark, or hardened-shaft compatibility is required, the locking (clamp) collar replaces the simpler set-screw collar — see the comparison table above for the trade-off. AIMS stocks locking collars in mild steel zinc-plated and 304/316 stainless across metric (6-100mm bore) and imperial sizes. For shaft-to-hub locking devices with higher torque transmission than a collar alone, see the related locking assemblies range — keyless shaft-hub connections used where slip-free torque transfer is the priority.