January 19, 2025
Pins are used in millions of consumer and industrial products. Pins are one type of precision fastener. They come in an unlimited variety of materials, shapes, and sizes and are commonly used to align and hold parts and assemblies together.
Precision pins are machined to hold two components together when a threaded screw or bolt shouldn’t or can’t be used. Most pins are semi-permanent, which means they can be removed and replaced fairly easily.
Pins are a simple part that’s usually cylindrical and without threading. Different types of pins are used in different capacities.
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Dowel Pins: Precision dowel pins are short cylinders that keep multiple components in proper alignment. Dowel pins are usually solid metal and can be machined using stainless steel, brass, carbon steel, and nearly every other metal. You’ll find dowel pins used in furniture assemblies, but wooden dowel pins usually aren’t as precise as metal pins. Dowel pins are available in high-precision tapered, slotted, spiraled, stepped, and grooved designs.
Spring Pins: A spring pin, or rolled pin, is a hollow or coiled cylinder of metal—usually rolled steel. Spring pins are slightly larger than the hole they’re used for to provide a snug fit, and a chamfered edge on one or both ends to help facilitate starting the pin into the hole.
Grooved Pins: Grooved pins are solid dowel pins that have grooves running down lengthwise. Grooved pins don’t have less material. Instead, the grooves are swaged, which displaces material and increases the diameter of the pin. The grooves close when the pin is forced into a hole, which gives grooved pins more elasticity than standard dowel pins. Similar to spring pins, there is a pilot or taper on the end to help get the pin started.
Locating Pins: Locating pins are precision-ground cylindrical components designed for precise part alignment and positioning. They typically feature a tight diameter tolerance and can include features like shoulder stops, threaded ends, or press-fit sections. Locating pins are commonly used in manufacturing fixtures, assembly jigs, and mold designs where repeatable positioning is critical.
Taper Pins: Taper pins are precision fasteners that feature a gradual slope from one end to the other, typically with a 1:50 ratio taper. This design allows for an extremely tight, self-locking fit when driven into reamed holes. Taper pins are widely used in machinery, tools, and precision equipment where vibration resistance and high load capacity are required.
You can find pins nearly everywhere. Since we’re focusing on pins with more precision dimensions, they’re most commonly used in the automotive, electronic, aerospace, and defense industries. When the right materials are used, precision pins provide a secure bond between two metal parts, and they can withstand a decent amount of pressure.
Precision pins need to be manufactured precisely and with care to fulfill their purposes.
These can be found in industries where high standards and tight tolerances are necessary. Precise machining is required for pins being used in the aerospace and automotive industries.
Other applications where you can find precision pins include electronics, mining tools, plumbing, and power distribution. The power distribution industries are some of the most common users of precision pins. This type of pin is used for shafts, male connector pins, mechanical applications, and more.
Because the pin is in constant contact with other metal parts, the material used for pins needs to be complementary to the surrounding materials. It's also essential to consider the environmental circumstances of the assembly– if there's going to be moisture or chemicals present, or constant temperature changes. Most pins are constructed with harder metals like steel, stainless steel, carbides, or superalloys like Monel or Hastelloy. Some applications may require softer materials. These materials are usually brass, aluminum, or mild steel.
In agricultural and heavy equipment applications, carbon and alloy steels with zinc or chrome plating are commonly used for their durability and resistance to outdoor conditions. These pins must withstand high mechanical loads, dirt, and varying weather conditions. Chemical processing equipment requires highly corrosion-resistant materials like Hastelloy C-276 or high-nickel alloys to handle aggressive chemicals and high temperatures.
Industrial pump and hydraulic systems often utilize 17-4 PH stainless steel or 400-series stainless steel pins due to their combination of strength and good corrosion resistance in fluid-handling applications. For measurement and instrumentation equipment, 300-series stainless steel and brass pins are preferred for their dimensional stability and resistance to oxidation, ensuring long-term accuracy of the instruments.
Secondary processes are also used to improve the durability of the pins. It's very common for pins to be galvanized, plated, heat treated, or anodized to increase the hardness and corrosion resistance of the metal.
There are many different ways to manufacture pins. Since most pins are ordered in large quantities, high volume machining methods like cold heading, spring pin machines, and Swiss screw machines are used.
The most common production process is called cold heading. Cold heading is the best way to manufacture high quantities of precision pins from a variety of metals.
The cold heading process starts with a long wire of metal, and then cuts the wire into smaller pieces called slugs. Then, the cold heading machine presses the slug into the desired shape. Depending on the specifications of the pin, there are one or multiple unique presses.
The cold heading machine uses a series of powerful hammer-like movements and dies to form the desired shape and dimensions. Since pins are a more simple shape than most parts, this process is more efficient than CNC machining. Cold heading allows rapid production of high quantities while maintaining tolerances within 50 microns (0.0002 inches).
For spring pins and rolled pins, a different type of machine is used. A spring pin machine takes a flat strip of metal and rolls the material into the desired pin shape, length, and thickness. This process is also ideal for high quantities and is relatively cheap compared to other machining processes.
Swiss screw machines are used to machine more complex precision pins. These machines specialize in making small, cylindrical shaped parts. The Swiss screw machine has exceptional precision, maintaining tolerances of ±0.005mm (0.0002in). This machining method is also efficient for high-volume orders because it can run automatically for hours without human involvement.
When selecting precision pins for an application, several key factors must be considered to ensure optimal performance and longevity.
Load requirements are particularly critical - engineers must account for both static and dynamic loads, shear strength requirements, and any cyclic stress the pin may encounter during operation. Installation and removal requirements also play a major role, as some applications need frequent maintenance access while others are meant for semi-permanent assembly.
Tolerance specifications are essential for precision pin applications and directly impact functionality. Critical diameter tolerances typically range from ±0.0002" to ±0.001" depending on the application. These tight tolerances ensure proper fit and prevent issues like excessive play or installation difficulties. The orientation of the pin and its mating holes must also be considered, as misalignment can lead to premature wear or failure.
Surface finish requirements vary based on the application but are crucial for proper pin function. A smoother surface finish generally provides better wear resistance and easier installation but comes at a higher manufacturing cost. Common surface finish specifications range from 16-63 microinches Ra, with more precise applications requiring finishes as smooth as 8 microinches Ra.
Cost considerations extend beyond just the initial pin price. While simpler pins like standard dowel pins are relatively economical, specialized designs such as grooved or floating pins command premium prices due to more complex manufacturing processes. Material selection significantly impacts cost - standard carbon steel pins are typically most economical, while specialized alloys or stainless steel versions can cost several times more. Production volume also affects pricing, with high-volume orders allowing for more efficient manufacturing methods.
Spex offers a large selection of custom precision pins and rollers for whatever your project needs. We are an ISO 9001:2015 certified machine shop, and our team specializes in precision machining and supply chain efficiency. Our machined components are available in an array of different materials and finishes and are manufactured to meet all the highest quantity needs.
Reach out to our team to get a quote for your next project.