Shaft Collar Types

Legacy context

This site is an independent educational reference on motion-linkage components, focusing on universal joints and shaft collars. The material presented here is drawn from preserved historical engineering literature and is offered for study and general understanding.

Key point 1

Readers will find an overview of shaft collar types, including set-screw, clamp, and threaded designs, along with their typical applications. The archived excerpts also describe a split-block universal joint design, notable for its heat-treated wear parts, replaceable bushings, and positive lubrication reservoir. These details are presented as historical examples of engineering practice, not as current product offerings.

Key point 2

No company affiliation, certification, or commercial endorsement is implied. The content is intended solely to illustrate mechanical principles and design variations found in earlier industrial catalogs. For current specifications or purchasing guidance, consult a qualified engineer or modern supplier.

Shaft Collar Types: A Calculation Walkthrough for B2B Sourcing and Design

Shaft collars are deceptively simple components. In a home workshop or light B2B production environment, they serve as locating devices, thrust surfaces, or simple stops. However, selecting the wrong type or size leads to shaft scoring, axial slippage, or outright failure under load. This guide walks through the engineering calculations behind the three main collar types—set screw, clamp, and threaded—so you can specify with confidence.

1. The Core Decision: Set Screw vs. Clamp vs. Threaded

Before any math, understand the mechanical difference. A set screw collar transmits axial force through point contact between the screw tip and the shaft. A clamp collar uses a circumferential bolt to close a split gap, creating uniform radial friction. A threaded collar engages with a mating thread on the shaft, converting rotation into axial motion.

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For B2B home DIY applications (e.g., jigs, light conveyor rollers, or adjustable stops), the decision tree is simple:

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• Set screw: Use when axial load is low (< 100 N), shaft hardness is below 40 HRC, and you need quick repositioning.
• Clamp: Use when you need high holding torque, cannot mar the shaft, or will reverse axial load direction.
• Threaded: Use only when the shaft is already threaded or you need precise micrometer-level adjustment.

2. Calculation Walkthrough: Set Screw Holding Force

The holding force of a set screw collar is limited by the screw’s indentation into the shaft. The formula for axial holding force (F_axial) is:

F_axial = (T_screw × μ) / (r_screw × tan(α + φ))

Where:

• T_screw = tightening torque on the set screw (N·m)
• μ = coefficient of friction between screw tip and shaft (typically 0.15–0.25 for steel on steel)
• r_screw = effective radius of the screw tip contact (m)
• α = lead angle of the screw thread (degrees)
• φ = friction angle, arctan(μ)

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Worked example: A 10 mm shaft with an M6 set screw. You tighten to 5 N·m. Assume μ = 0.2, r_screw = 0.0015 m (1.5 mm tip radius), α = 3.5 degrees, φ = arctan(0.2) = 11.3 degrees.

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First, convert angles to radians for calculation: α = 0.0611 rad, φ = 0.197 rad. tan(α + φ) = tan(0.258) = 0.263.

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F_axial = (5 × 0.2) / (0.0015 × 0.263) = 1.0 / 0.0003945 = 2535 N.

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That is the theoretical static holding force. However, real-world derating is essential. Vibration, thermal cycling, and shaft surface finish reduce this by 50–70%. So your safe working load is roughly 750–1250 N. If your application exceeds that, switch to a clamp collar.

3. Calculation Walkthrough: Clamp Collar Friction Torque

A clamp collar’s holding capacity depends on the radial force generated by the clamping bolt. The axial force (F_axial) is:

F_axial = (2 × F_bolt × μ) / (1 + (D_shaft / D_collar)²)

Where:

• F_bolt = preload from the clamping bolt (N)
• μ = friction coefficient between collar bore and shaft (0.12–0.18 for dry steel)
• D_shaft = shaft diameter (m)
• D_collar = outer diameter of the collar at the bolt centerline (m)

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Worked example: A 20 mm shaft, collar outer diameter 40 mm. You use an M8 bolt torqued to 20 N·m. For an M8 bolt, preload F_bolt ≈ 0.7 × yield strength × tensile stress area. For a grade 8.8 bolt, yield ≈ 660 MPa, stress area ≈ 36.6 mm². F_bolt = 0.7 × 660 × 36.6 = 16,900 N.

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Assume μ = 0.15. D_shaft = 0.020 m, D_collar = 0.040 m. Ratio squared = (0.020/0.040)² = 0.25.

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F_axial = (2 × 16,900 × 0.15) / (1 + 0.25) = 5070 / 1.25 = 4056 N.