Why Choose Micro Pins?
Micro pins are used in precision and small-scale assemblies where standard pin sizes are too large for the application. Dowel pins provide accurate, repeatable alignment between mating components. Cotter pins provide positive retention to prevent axles, clevis pins, and other fasteners from backing out or sliding free under load or vibration. Both types are essential hardware for small mechanical assemblies where standard pins would not fit the bore, hole, or clevis diameter.
This category includes micro dowel pins and micro cotter pins in diameters from 1/32" through 1/8", available in 18-8 stainless steel, 316 stainless steel, brass, and zinc plated steel depending on pin type.
Micro Dowel Pins
Micro dowel pins are solid, precision-ground cylindrical pins used to accurately align two mating components during assembly and to maintain that alignment under load. They are installed into closely toleranced holes in both mating parts and held in place by the interference fit between the pin and the hole.
Micro dowel pins on this page are available in 18-8 stainless steel and 316 stainless steel in diameters from 1/32" through 1/8". Each pin is ground to a close diameter tolerance, with a maximum and minimum diameter specified for each size. The tight tolerance ensures the pin fills the hole precisely with the correct amount of interference or transition fit to hold position without play.
Micro Dowel Pin Sizes and Tolerances
Micro dowel pins on this page are available in the following diameters with ground tolerances:
- 1/32" diameter
- 1/16" diameter (max .0628" / min .0626")
- 3/32" diameter (max .0941" / min .0939")
- 1/8" diameter (max .1253" / min .1251")
The tolerance range for each size is very tight, typically within .0002". The mating hole must be drilled and reamed to a matching tolerance to achieve the correct fit. Use a reamer rather than a drill alone when precision dowel pin fit is required, as drilled holes are rarely accurate enough to achieve a proper dowel fit without reaming.
Micro Cotter Pins
Micro cotter pins are small two-legged wire pins that pass through a transverse hole in a shaft, clevis pin, axle, or bolt and are then bent open to lock the assembly in place. They are a simple, low-cost retention device that prevents axial movement of the component they secure. Once bent, a cotter pin must be straightened to remove, making it a single-use fastener in most applications.
Micro cotter pins on this page are available in 18-8 stainless steel, 316 stainless steel, brass, and zinc plated steel in diameters from 1/16" through 1/8". Choose the cotter pin diameter based on the hole size in the shaft or pin being secured.
Micro Cotter Pin Sizes and Materials
Micro cotter pins on this page are available in the following diameters:
- 1/16" diameter
- 3/32" diameter
- 1/8" diameter
Available materials for micro cotter pins:
- 18-8 Stainless Steel (good corrosion resistance for most general applications)
- 316 Stainless Steel (better chloride and saltwater resistance for marine and coastal applications)
- Brass (non-magnetic, conductive, corrosion resistant)
- Zinc Plated Steel (economical general purpose option for dry indoor environments)
How to Select the Right Cotter Pin Size
The cotter pin diameter should match the hole drilled through the shaft or clevis pin it will secure. The hole diameter is typically slightly larger than the cotter pin wire diameter to allow the pin to pass through easily. As a general rule, the cotter pin diameter should be approximately 1/16" to 3/32" smaller than the shaft diameter it secures. Refer to the equipment specifications or the existing hole size when selecting a replacement cotter pin.
Cotter pin length should be selected so that enough leg length extends beyond the hole to be bent securely against the shaft or clevis. A pin that is too short may not bend sufficiently to retain the assembly under vibration.
Micro Dowel Pins vs Cotter Pins
Micro dowel pins and micro cotter pins serve different functions and are not interchangeable. Dowel pins are alignment and positioning components pressed or driven into precisely toleranced holes in mating parts. They locate and lock components in a fixed spatial relationship and are removed by pressing or driving them out of the hole. Cotter pins are retention components that pass through a loose clearance hole in a shaft or pin and are bent to prevent axial removal. They do not provide alignment and are not press-fit.
Use micro dowel pins when two mating components need to be aligned precisely and repeatedly in the same position. Use micro cotter pins when a shaft, axle, or pin needs to be retained in place and prevented from sliding out of its bore or clevis.
Micro Dowel Pin Materials
Micro dowel pins on this page are available in 18-8 stainless steel and 316 stainless steel. 18-8 stainless provides good corrosion resistance and is suitable for most precision assembly applications. 316 stainless provides better resistance to chlorides and saltwater and is preferred for marine, medical, and coastal applications where higher corrosion resistance is needed.
Stainless steel dowel pins are well suited to applications where the pin will be installed and removed periodically, as stainless is harder and more wear resistant than brass or zinc plated steel at small diameters.
Installing and Removing Micro Dowel Pins
Micro dowel pins are installed by pressing or lightly tapping them into the reamed hole in the mating component. At very small diameters such as 1/32" and 1/16", use care during installation to avoid bending the pin. A proper fit should require light to moderate force to install. If a pin goes in too easily, the hole may be oversize and a larger pin or different tolerance may be needed.
To remove a micro dowel pin, press it out from the opposite end using a punch or drift sized just smaller than the pin diameter. Do not pry or lever micro dowel pins at small diameters, as the pin can bend and become difficult to remove or may damage the hole.
Related Categories
Micro Pins FAQs
What is the difference between a dowel pin and a cotter pin?
A dowel pin is a solid precision-ground cylinder pressed into closely toleranced holes in mating components to align and locate them accurately. A cotter pin is a two-legged wire pin that passes through a loose hole in a shaft or clevis pin and is bent open to prevent the assembly from sliding apart. Dowel pins provide alignment. Cotter pins provide retention.
What diameter micro dowel pins do you carry?
Micro dowel pins are available in 1/32", 1/16", 3/32", and 1/8" diameters in 18-8 and 316 stainless steel. Each size is ground to a tight diameter tolerance to ensure a precise fit in the mating hole.
What diameter micro cotter pins do you carry?
Micro cotter pins are available in 1/16", 3/32", and 1/8" diameters in 18-8 stainless steel, 316 stainless steel, brass, and zinc plated steel.
Are cotter pins reusable?
Cotter pins are generally considered single-use fasteners. Once bent open during installation, straightening and rebending the pin weakens the wire and increases the risk of breakage. In most applications, replace the cotter pin with a new one any time the assembly is disassembled.
What hole size do I need for a micro dowel pin?
The mating hole for a dowel pin should be reamed to match the pin diameter tolerance. The hole should be drilled undersize and then reamed to the final diameter. The resulting fit should be an interference or light press fit, requiring light to moderate force to install the pin. Drilled holes alone are typically not accurate enough for a proper dowel fit without reaming.
Do you sell micro pins in bulk?
Yes. Micro dowel pins and cotter pins are available in bulk quantities. Contact us for pricing on large or recurring orders.