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Hartford Technologies Blog

7 Things to Know When Buying Precision Pins

Posted: Mar 30, 2022 11:46:56 AM

Precision pins used in manufacturing, whether soft or hardened, are made to withstand thousands of hours of use without failure. They are broadly used across various applications in many industries, including: aerospace, electrical motors, hydraulic equipment, instrumentation, tooling and fixtures, machinery, military and many more.

Hartford Technologies goal is to help simplify the buying process for the sometimes complex and confusing category of precision pins.

1. What is a precision pin? 

Precision pins are solid, headless, cylindrical shaped straight metal pins with a centerless ground finish. Manufactured to precise fractional diameters and lengths, dowel pins come in a variety of sizes, styles, designs and materials.  

The only exception is the knurled pin, which is not precision ground, but has a unique surface finish that comes in several different configurations such as diamond, straight, or helical. Tolerances on knurled pins are not as precise as ground pins.

2. What materials and platings are available?

Precision pins are available in many materials: high carbon steel, 52100, GCr15, all typically hardened to ~62HRC and stainless steel grades 18-8/303, 316 (soft) and 416 (typically hardened). Other exotic materials or special finishes are available for special order.

3. What sizes are available?

Hartford Technologies can manufacture inch sizes from 1/16″ to 1″ diameter, and metric from M1 to M20 diameter. Length options vary by diameter. Other diameters and special lengths are available for special order and usually involve an extended lead time.

4. When ordering, do I need to specify the pin tolerance or call out attributes such as standard, undersized or oversized fit?

Diameter and length tolerance are some of the most important facets of the precision pin and need to be specified when ordering. The most common standard inch or imperial-sized precision dowel pin is made to the ASME ANSI B18.8.2 spec, has a diameter tolerance of -0.00 / +0.0002 and length tolerance of +/-0.010. For example, a ¼” (0.25) diameter standard dowel pin will have a diameter between 0.2500–0.2502″.

The standard metric tolerance is related to the DIN. Both DIN 7 and DIN 6325 have a standard m6 diameter tolerance of +0.012mm / +0.004mm and a length tolerance related to the specific pin length.

Undersized series dowel pins are used for inconsistent holes. They have a basic diameter 0.0002″ under the nominal diameter. For example, a ¼” (0.25) diameter undersized dowel pin will have a diameter between 0.2500–0.2498″.  The Mil-P-21143/2- falls into the undersized category.

5. What information do I need for ordering?

The simplest way is to provide your blueprint to Hartford Technologies. However, if you only know size requirements,  we can create a blueprint for you and clearly identify end configuration, tolerances, and material type. To order by description, you will need the diameter, length and material, and if applicable, any special tolerance, plating or style requirements. 

6. What are the pin type/end configuration options?

The pin style will depend upon the specifications and the material. Precision pins may come with either a double chamfer or a radius on one end and a chamfer on the other end. Specific style requirements are available for special order and usually involve a longer lead time.

Straight End w/Chamfer

Straight End with radius (deburred)

Spherical End

Pointed Ends

Knurled Pin (Diamond pattern)

Rounded w/chamfer


7. What level of certification is required?

Generally, a Certificate of Conformance or a COC is sufficient. Full certification with material certs and measurement test reports are available upon request.

About Hartford Technologies 

Hartford is a leading manufacturer of the precision pins used in many different industry assemblies. Hartford custom manufactures precision shafts and pins to your specifications, with length and diameter tolerances depending upon the size and end configuration. To request a quote or learn more, contact Hartford today.