Why Shoulder Locating Pins Are Important
Shoulder Locating Pins are used to locate workpieces for machining, welding, inspection and assembly on jigs, fixtures and tooling plates. These pins have a stepped shoulder, a larger-diameter part that limits how far in they can be inserted and prevents them from bottoming out or going all the way through the plate rather than pressing all the way into a receiving bore.
The shoulder geometry solves the double placement concerns. First, it establishes a repeatable Z-axis datum: a workpiece sitting against the shoulder face is at the same height relative to the fixture body. Shouldered pins will take heavier workpieces and lateral pressures while clamping or cutting. The bigger bearing surface spreads side loads over a wider area than a shank.
The alleviated flats of the diamond pin allow float along one axis to prevent over-constraint and thermal-lock binding in traditional two-pin locating arrangements. A circular Shoulder Locating Pin constrains X and Y Axis. This coupler enables repeatable fixture design in production from CNC workholding to injection mould bases.
Press-Fit, Threaded, and Renewable Mounting Styles
Key-CNC offers three mounting options for shouldered positioning pins: Press-Fit, Threaded, and Renewable.
The mounting end is interference-fitted (m6 tolerance) and pushed into the fixture body. This design is the simplest and cheapest for short-to-medium manufacturing runs with periodic pin replacement.
The fixture plate's tapped hole accepts the mounting end's M3–M20 metric thread. Due to their detachability, modular tooling systems, prototype fixtures, and applications that need pin replacement or reconfiguration prefer threaded pins.
Renewable (lockscrew) type-A hardened liner bushing is pressed into the fixture body, and the pin glides in with a light clearance fit and side lockscrew. This method permits worn pins be swapped without re-machining the fixture mounting hole for long production runs and high-cycle wear.
CNC Manufacturing: Turning, Grinding, and Heat Treatment
Key-CNC is a precision CNC machining enterprise with a 16+ year history in Shenzhen. There are a few methods for creating each pin. The blank is manufactured from bar stock on CNC equipment to provide coaxial shank, shoulder and head geometry. Pin bodies with G6 or tighter tolerances can be used to obtain tight tolerance locating diameters. The surface roughness can be reduced down to Ra 0.4-0.8 μm by cylindrical grinding.
Heat treatment is required for pin positioning. Tempered to HRC 55-62 (alloy tool steel) or HRC 50-55 (stainless) for pin wear life of thousands of load/unload cycles without size distortion. The process used at KEY-CNC is ISO 9001:2015 certified including batch specific hardness verification, material certificates and comprehensive dimensional inspection reports.
Shoulder to shank concentricity is 0.01 mm so the locating and mounting datums have a common axis. Concentricity is the difference between a precise Shoulder Locating Pin and a poorly produced step pin, a fixture that gives you repeatability and a fixture that gives you inaccuracy.
Material and Surface Treatment Options
|
Parameter |
Specification |
|
Material |
Alloy Tool Steel (SKD11/D2, SKS3), Alloy Steel (SCM435), Stainless Steel (SUS304, SUS440C), Carbon Steel |
|
Hardness |
HRC 45–63 (material and heat treatment dependent) |
|
Pin Diameter |
Ø 2–30 mm (metric); 1/16″–1.25″ (inch) |
|
Tolerance |
g6 standard; ±0.01 mm on request |
|
Surface Roughness |
Ra 0.4–0.8 μm (ground); Ra 0.8–3.2 μm (turned) |
|
Tip Shape |
Round, Diamond, Conical, Bullet-nose, Flat |
|
Shoulder Style |
Single-shoulder, Double-shoulder, Flanged |
|
Mounting Type |
Press-fit (m6), Threaded (M3–M20), Renewable (liner + lockscrew) |
|
Surface Finish |
Black oxide, Hard chrome plating, Passivation, TiN coating, Precision ground |
|
Quality System |
ISO 9001:2015; RoHS compliant |
|
Lead Time |
Samples: 5–10 working days; Production: 10–15 working days |
Frequently Asked Questions
Q: What should be the tolerance on the locating pin and the mating hole?
A: For a close sliding fit use a g6 pin in a reamed H7 hole for the main locating pin. Clear one axis to secondary (diamond) pin, for example H7/g6, with 0.005–0.010 mm diamond flat relief. KEY-CNC determines tolerances according to drawings. KEY-CNC provides stack-up tolerance analysis.
Q: Shoulder Locating Pins, press-fit or threaded - how to choose?
A: The simplest and most economical way of permanently fitting medium run fixtures is press fitting. Threaded pins are well suited for modular tooling, prototype fixtures and pin replacement where wear is a factor. For heavy wear, long run applications use the renewable (liner + lockscrew) design to change pins without re-machining the fixture body.
Q: Are multi-step pins or non-standard shoulder diameters available at KEY-CNC?
A: Yes. We can manufacture Custom Shoulder Locating Pins to non-standard shoulder diameters, double shoulders, multi-step combinations, pull ring heads and anti-rotation flats to your print. Send a 2D sketch or STEP file for a quote in 24 hours.
Q: What is the best surface treatment for my application?
A: General machining fixtures benefit from the low cost and glare reduction of black oxide. 750 HV+ hard chrome plating enhances the durability of high-cycle pins. Cleanroom or food-grade stainless pins need passivation. Coupling wear and corrosion resistance of TiN coating for semiconductor tools
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