How to Select Plastic DowelsHow to Select Wooden DowelsHow to Select Metal Dowels

Images credits: Wilton Dowels; Dick Blick; Wikimedia

 

Dowel pins are industrial fasteners that are used to assemble two or more items together. They are short, cylindrical rods. The dowel pins can be tapered, slotted, grooved, or otherwise altered to change its mechanical properties. They are commonly available in imperial or metric units.

 

Dowel Pin Operation

Dowel pins do not possess moving or actuated components. Dowel pins' mechanical capabilities stem from their high coefficient of friction, and any adhesive that may be applied when they are inserted into press-fit predrilled holes. They must be rigid while in use so they are capable of keeping the assembled parts aligned without further hardware fastening. For a firm fit, the hole should be exactly the same size or slightly smaller than the dowel's diameter. Dowel pins typically have working loads identified, with a breaking strength measured as when a double shear occurs. 

 

Dowel pin operation application use

Image credit: Craftsman Space

 

For aesthetic applications where the hardware must be accessible or seen, a dowel pin can appear uniform to its assembly--a distinct advantage over other fasteners. For this reason, dowels are commonly used in furniture. They can also be applied as hinges and simple axles.

 

Dowel Production

Wooden dowel rods are produced on the same mill machinery that produces other finished cylindrical wood products, like fence poles and furniture pieces. Dowel pins are shortened lengths of full-sized dowels. These dowel pins are usually of hard wood, like birch or maple. Dowel pins may undergo a secondary operation, such as planing or grooving, if desired.

Video credit: Montana Hyrdaulics via Youtube

 

Metal dowel pins undergo a melt and cast process, as indicated by the infographic below:

Images credit: Timken Co.

 

Common metal materials for dowel pin manufacture include:

  • Aluminum, which is light, ductile, conductive, and very resistance to oxidation.
  • Brass is strong, ductile, conductive, corrosion resistant, and demonstrates low magnetic permeability.
  • Stainless steel has a high pressure rating, and is chemical and corrosion resistant.
  • Steel that is hardened and ground is compacted to produce a very hard, though brittle, metal. It has gone through a hardening process such as quenching or induction. Unhardened steel is more malleable, but is still suitable for many applications.
  • Titanium is strong, with good temperature and corrosion resistance. It is 44% lighter than steels.

Plastic dowels are formed via plastic injection molding.

Video credit: Society of Manufacturing Engineers via Youtube

 

Dowel Pin Sizing

After material, dowel pin sizing is the other major specification manufacturers need to consider.

How to Determine Dowel Size Dimension Geometry

 

  • Outer diameter is the measurement across the edges that form the dowel pin's width.
  • Length is the measurement of the dowel's longest cross section.

Most dowels produced are of the straight dowel variety. A dowel may have diameter tolerances of ± .010 inches compared to the dowel pin's nominal size. This tolerance ensures that the dowel mates in either a loose-fit or press-fit fashion with its corresponding hole. If the pin has two separate tolerances on each end, it is considered a 'parallel pin'.

 

Dowel Pin Configurations

There is a limited number of dowel pin types.  Locating pins, cotter pins, and spring pins have their own unique GlobalSpec selection guide and specification filter. A straight pin with metric or SAE threads is called a threaded rod.

  • Drive pins have an interference fit and must be hammered into a mating hole. They are common for rotary and moving applications.

How to Select Drive Pins

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  • Escutcheon pins are used for light duty applications. With a small head and tapered end, these pins are usually hammered into place.

How to Select Escutcheon Pins

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  • Groove pins are engraved with longitudinal grooves. These grooves are meant for adhesives to relieve hydraulic pressure and improve holding.

How to Select Groove Pins

Image credit: Nordex Inc.

  • Knurled pins have a knurled surface to enhance the dowel pin's grip. It is common for decoration and where parts are locked or keyed together in assemblies. Straight, helical, and diamond knurls are common.

How to Select Knurled Dowel Pins

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  • Pull dowel pins have a threaded hole at one end so a screw can be inserted to assist removing the pin from a blind hole.

How to Select Pull Dowel Pins

Image credit: ABC Fastener Group Inc.

  • Spiral-groove dowel pins have longitudinal, helical grooves. They provide additional friction, and expansion space for adhesive.

How to Select Spiral Groove Dowel Pins

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  • Stepped dowel pins have two or more different body diameters.

How to Select Stepped Dowel Pins

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  • Tapered pins have a taper rate of 1/4" per foot from the larger diameter to the smaller diameter. 

How to Select Tapered Dowel Pins

Image credit: Ravi Engineering Co.

  • Threaded taper pins are similar to a regular tapered pin, but with helical grooves along one of the diameters.

How to Select Threaded Taper Dowel Pins

Image credit: Senior Graphics Limited

Resources

 

ABC Article Directory - Technology - Dowel Pin Handbook

 

Wikipedia - Dowel

 

McMaster-Carr - Dowel Pins

 

E & T Fasteners - Molder Plastic Dowels

 

Tooling U - Overview of Non-Threaded Fasteners - Class Vocabulary

 

Fostermation

 

Groov-Pin Corp. - Groove Pins

 

Warwick Fasteners - Dowel Pins.pdf