What the heck are Dowel Pins?

Dowel Pins

Welcome back to our “what the heck is that” series, where we discuss some of the unique fasteners and electronic hardware that manufacturers use in the design and assembly of their products. Today, we will introduce you to the Dowel Pin.

What is a Dowel Pin? 

If you have ever shopped at Ikea or assembled furniture on your own, then you are familiar with the peg shaped non-threaded wooden pins that are used to join parts together, aka as a Dowel Pin.

For the purposes of manufacturing, Dowel Pins are solid, headless cylindrical shaped straight metal pins with a centerless ground finish. Typically hardened and manufactured to precise fractional diameters and lengths, Dowel Pins come in a variety of sizes, styles, designs and materials that cause confusion among buyers, engineers and end-users alike! Today, we will try simplify this confusing category of fasteners.

Who uses Dowel Pins?

Dowel Pins are used as a hinge, shaft or pivot to locate or hold parts together within a precision assembly or a fixture.

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.

Dowel Pins are popular within assemblies since they can withstand frequent insertion and removal without distortion.  And production favors pins since they require no extra fastening hardware for insertion, no secondary operations and no mating parts.  All this adds up to speedier production, which makes everyone in the food chain happy!

What do I need to consider when selecting Dowel Pins?

Although Dowel Pins are offered in a multitude of materials and styles, when it comes to the main commercial and Mil-spec offerings, there are a few main issues to consider.

Standard, Oversized or Undersized?

Standard series Dowel Pins are used for initial applications.  They have a basic diameter 0.0002 inch over the nominal diameter. For example, a ¼ standard dowel will have a diameter between .2501-.2503.

Oversized series Dowel Pins are usually used to fit into worn holes and are generally used in the aftermarket for repairs.  They have a basic diameter 0.001 inch over the nominal diameter. For example, a ¼ oversized dowel will have a diameter between .2509-.2511.

Undersized series Dowel Pins are used for inconsistent holes.  They have a basic diameter -0.0002 inch under the nominal diameter.  For example, a ¼ undersized dowel will have a diameter between .2500-.2498. The Mil-P-21143/2- falls into the undersized category.

Chamfer or radius on the end?

In general, commercial pins are made to inch standard ANSI ASME B18.8.2.  Standard alloy pins will have a radius on one end and a chamfer on the other end.  However, stainless steel Dowel Pins are often manufactured with a chamfer on both ends.

Commercial or Military?

If you or your customer needs domestically made, DFARs pins to the most exacting standards, then military may be the right pin for you!

Alloy or stainless? And which stainless for that matter?

Alloy Steel is the strongest pin available and is hardened. It can be finished with Black Oxide to provide greater rust resistance than plain alloy.

Type 416 Stainless steel is the strongest standard stainless steel offering, and is the material used for MS16555 and MS16556 series.  Magnetic.

Type 18-8/303 Stainless Steel is the most commonly available stainless offered and is the standard material offered for Mil-P-21143 series.

Type 316 Stainless Steel is the most corrosion resistant stainless available and does not correlate to a Mil-spec part.

Are there other factors to consider?

Dowel Pins often show up under their Mil-spec numbers, which can be crossed to commercial equivalents. Some common Mil-spec series for Dowel Pins include Mil-P-21143 (303 Stainless), MS16555 (standard series offered in both alloy and 416 Stainless Steel) and MS16556 (oversized series offered in both alloy and 416 stainless steel).

If you are not ordering by an MS or NAS Mil-Spec part number, then inch Dowel Pins conform to ANSI/ASME B18.8.2.  For commercial pins, be mindful to specify the material and size tolerance that you need. Unless noted, Dowel Pins are precision ground, hardened and heat treated to meet the proper Rockwell hardness.

And remember, no hammers! When installing Dowel Pins, never drive the pin into the hole with force, always press it in for best results.

Dowel Pins at MF Supply

We offer:

The full range of commercial and mil-spec parts, including parts that are DFARS and ROHS compliant.

Brand names and generic equivalents.

Custom made parts per print in non-standard and exotic materials and finishes.

Inch and Metric sizes including DIN 7, DIN 6325, and ISO 2338 and 8734


For more detailed information on Dowel Pins, visit us at http://www.mfsupply.com/dowel_pins_s/1925.htm