Last revised: January 15, 2025

Dowel pins are industrial fasteners that are used to join two or more items together. They are short, cylindrical rods made of various materials including wood, metal and plastic. 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.

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 planning or grooving, if desired.

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

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.

Dowel Pin Sizing

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

• 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.'

Configurations

There is a limited number of dowel pin types. Locating pins, cotter pins, and spring pins have their own unique Engineering360 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.
Escutcheon pins are used for light duty applications. With a small head and tapered end, these pins are usually hammered into place.
Groove pins are engraved with longitudinal grooves. These grooves are meant for adhesives to relieve hydraulic pressure and improve holding.
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.
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.
Spiral-groove dowel pins have longitudinal, helical grooves. They provide additional friction, and expansion space for adhesive.
Stepped dowel pins have two or more different body diameters.
Tapered pins have a taper rate of 1/4" per foot from the larger diameter to the smaller diameter.
Threaded taper pins are similar to a regular tapered pin, but with helical grooves along one of the diameters.

Dowel Pins FAQs

What are the key factors to consider when selecting the right dowel pin for a specific application?

When selecting the right dowel pin for a specific application, several key factors should be considered to ensure optimal performance and compatibility. Here are the main considerations:

Function of the Pin: Determine the primary role of the dowel pin in the assembly. Is it for alignment, load-bearing, or as a hinge? This will influence the type and material of the pin you choose.

Strength Requirements: Assess the mechanical strength needed for the application. This includes understanding the forces the pin will be subjected to and selecting a material that can withstand these forces without failure 

Material of the Component: Consider the material of the components in which the dowel pin will be used. The compatibility between the pin material and the component material is crucial to prevent corrosion and ensure a secure fit.

Environmental Conditions: Evaluate the environment where the dowel pin will be used. Factors such as temperature, humidity, and exposure to chemicals can affect the choice of material and coating for the pin.

Product Lifetime and Cycles: Consider the expected lifetime of the product and the number of cycles the dowel pin will undergo. This will help in selecting a pin that can endure the required operational lifespan.

Installation Method: Determine how the dowel pin will be installed. Some pins require precise machining of holes and higher installation forces, which can impact manufacturing costs and time.

Volume of Production: Consider the expected production volume. High-volume applications might benefit from different pin types or materials to optimize cost and efficiency.

Aesthetic Considerations: For applications where the dowel pin is visible, such as in furniture, the appearance of the pin might be a factor. Uniformity with the assembly can be an advantage.

These factors will guide you in selecting the most suitable dowel pin for your specific application, ensuring both functionality and cost-effectiveness.

What is the installation process for dowel pins?

The installation process for dowel pins involves several important considerations to ensure a secure and precise fit. Here are the key steps and factors involved in the installation process.

Precision Machining of Holes

The holes where the dowel pins will be inserted must be precision machined. This is crucial for achieving the necessary press fit between the pin and the host components. The precision of the holes directly affects the alignment and stability of the assembly.

Material Displacement

Solid dowel pins rely on material displacement between the pin and the host components for the press fit. This means that the pin must be slightly larger than the hole to create a tight fit. This requires careful consideration of the tolerances involved.

Installation Force

Installing solid dowel pins requires a considerably higher installation force compared to other types of pins, such as spring pins. This is due to the need for material displacement to achieve the press fit. Proper tools and techniques must be used to apply the necessary force without damaging the components.

Consideration of Pin Type

The type of dowel pin used (e.g., solid ground dowel, coiled spring pin) can affect the installation process. Each type has different requirements for hole preparation and installation force, so it's important to choose the appropriate pin type based on the specific application needs.

What are the specific applications of aluminum in the aerospace industry?

Aluminum is extensively used in the aerospace industry due to its advantageous properties. Here are some specific applications and reasons why aluminum is preferred in this sector:

Structural Components

Aluminum alloys are predominantly used in the construction of aircraft fuselages, wings, and supporting structures. This is due to their high strength-to-weight ratio, which is crucial for maintaining structural integrity while minimizing weight.

Cryogenic Applications

Aluminum alloys are ideal for cryogenic fuel tanks in rockets and launch vehicles because they do not become brittle at low temperatures and actually gain strength as the temperature decreases.

Fabricability

Aluminum is one of the easiest metals to form and machine, which allows for cost-effective manufacturing of complex aerospace components. This includes parts like brackets, housings, and manifolds, which are often cast from aluminum alloys.

Corrosion Resistance

The natural corrosion resistance of aluminum makes it suitable for use in environments where exposure to moisture or chemicals is a concern, extending the lifespan of aerospace components.

Historical and Modern Usage

Historically, aluminum alloys like Duralumin have been used since the early 20th century for aircraft construction. Modern aircraft continue to use advanced aluminum alloys for various structural applications, including fuselage skins and wing components.

These properties and applications highlight why aluminum remains a critical material in the aerospace industry, balancing performance, cost, and manufacturability.

What are the challenges associated with using aluminum in engineering applications?

When using aluminum in engineering applications, several challenges can arise despite its many advantages. Here are some of the key challenges associated with aluminum:

Welding Difficulties

Aluminum can be challenging to weld compared to other metals like steel. Ensuring consistent quality in arc fusion welds can be difficult, which is why alternative methods like friction stir welding are often preferred for high-integrity applications.

Fatigue Resistance

While aluminum is lightweight and strong, its fatigue resistance can be lower than that of other metals. This can be a concern in applications where components are subjected to repeated stress cycles.

Thermal Expansion

Aluminum has a relatively high coefficient of thermal expansion, which can lead to issues with dimensional stability in applications where temperature fluctuations are significant. This can affect the fit and function of components in precision assemblies.

Corrosion in Certain Environments

Although aluminum is generally corrosion-resistant, it can still corrode in certain environments, particularly when exposed to saltwater or acidic conditions. Protective coatings or anodizing may be required to enhance its corrosion resistance in such environments.

Cost of Alloying and Processing

The cost of producing aluminum alloys and the processing required to achieve desired properties can be higher compared to some other materials. This includes costs associated with heat treatment and forming operations.

These challenges need to be carefully considered and managed when designing and manufacturing components using aluminum to ensure optimal performance and longevity.

What are the welding techniques used for aluminum?

When it comes to welding techniques for aluminum, there are several methods that are commonly used due to the unique properties of aluminum. Here are some key techniques:

Friction Stir Welding (FSW)

FSW is a solid-state joining process that is particularly effective for aluminum. It is often the first choice for high-integrity, low-cost welding in industries such as aerospace, shipbuilding, and automotive. This technique is preferred because it avoids the common issues associated with arc fusion welding of aluminum, such as inconsistent quality.

Arc Fusion Welding

While aluminum can be challenging to weld using traditional arc fusion methods due to issues like porosity and cracking, it is still used in some applications. However, achieving consistent quality can be difficult, which is why alternative methods like FSW are often preferred.

TIG (Tungsten Inert Gas) Welding

TIG welding is a common method for welding aluminum, especially for thinner materials. It provides a high-quality weld but requires skilled operators due to the need for precise control over the welding process.

MIG (Metal Inert Gas) Welding

MIG welding is another technique used for aluminum, particularly for thicker materials. It is faster than TIG welding and is often used in industrial applications.

These techniques are chosen based on the specific requirements of the application, such as the thickness of the material, the desired weld quality, and the production volume.

Dowel Pins Media Gallery

References

GlobalSpec—Friction stir welding of aluminum alloys – Part 1

GlobalSpec—Manufacturing Technology for Aerospace Structural Materials