TM — Trusted Machinery

Material selection has a direct impact on the accuracy, durability, weight, maintenance requirements, and overall cost of a jig or fixture.

In practice, a custom jig or fixture is rarely made from only one material. Different materials are often combined according to the function of each component. For example, mild steel may be used for the main structure, while hardened tool steel is used for locating pins and wear components. Engineering plastics may also be added to protect finished surfaces from scratches.

The most suitable material therefore depends not only on strength, but also on production volume, required accuracy, operating environment, workpiece material, and expected service life.

Common Materials Used for Jigs and Fixtures

1. Tool Steels

Tool steels are commonly used for components that require high hardness, dimensional accuracy, and wear resistance.

Typical materials include:

• O1 tool steel
• A2 tool steel
• D2 tool steel

Common applications include:

• Locating pins
• Drill bushings
• Wear plates
• Guide components
• Replaceable inserts
• High-wear contact surfaces

Tool steel components are often heat-treated and precision-ground after machining. The correct material and heat-treatment process should be selected according to the required hardness, impact load, dimensional tolerance, and risk of deformation.

2. Alloy Steels

Alloy steels such as 4140 and 4340 provide a good combination of strength, toughness, and fatigue resistance.

They are suitable for components such as:

• High-load clamping arms
• Shafts and pivots
• Locating components
• Heavy-duty support blocks
• Structural parts subject to repeated loading

Depending on the application, alloy steel components may be heat-treated, nitrided, ground, or surface-coated to improve their service life.

3. Mild and Carbon Steels

Mild steel is widely used for general fixture structures because it is economical, readily available, weldable, and relatively easy to manufacture.

Common options include:

• 1018 low-carbon steel
• A36 structural steel
• Other equivalent low-carbon steels

Typical applications include:

• Fixture baseplates
• Welded frames
• Support structures
• Riser blocks
• Mounting plates
• Non-wearing components

1018 steel is suitable for many machined components, while A36 is more commonly used for welded frames and larger structural sections. Welded structures may require stress relief and finish machining when dimensional accuracy is important.

4. Aluminum Alloys

Aluminum alloys are used when low weight, corrosion resistance, and shorter machining time are important.

6061-T6 Aluminum

6061-T6 offers a practical balance of strength, machinability, corrosion resistance, and cost.

Common applications include:

• Lightweight baseplates
• Modular fixture plates
• Inspection fixtures
• Assembly jigs
• CNC soft jaws
• Moving parts in automated equipment

7075-T6 Aluminum

7075-T6 provides higher strength than 6061-T6 and is suitable for lightweight components subject to greater mechanical loads.

However, it is generally more expensive, less corrosion-resistant, and less suitable for welding than 6061-T6. Its use should therefore be evaluated according to the actual loading and manufacturing requirements.

Hard anodizing may be applied to aluminum components when improved surface hardness and wear resistance are required.

5. Cast Iron

Gray cast iron and ductile iron offer high compressive strength, good dimensional stability, and effective vibration damping.

Common applications include:

• Heavy machining fixture bases
• Angle plates
• Tombstone fixtures
• Machine mounting structures
• Inspection bases requiring dimensional stability

Cast iron is particularly useful for machining applications where vibration control and structural stability are more important than low weight.

6. Engineering Plastics

Engineering plastics are often used where the fixture comes into direct contact with finished, coated, polished, or delicate components.

POM/Acetal

POM, also known as acetal, offers low friction, good machinability, and relatively high dimensional stability.

Typical applications include:

• Non-marring part nests
• Workpiece supports
• Guide blocks
• Sliding components
• Electronic assembly fixtures

Nylon and UHMW-PE

Nylon and UHMW-PE provide good impact and abrasion resistance.

They are commonly used for:

• Wear strips
• Guide rails
• Protective supports
• Conveyor components
• Non-scratching contact surfaces

The operating temperature, chemical exposure, moisture absorption, loading, and dimensional tolerance should be considered when selecting an engineering plastic.

7. Composite and 3D-Printed Materials

Composite materials and industrial 3D-printed polymers can be useful for lightweight tooling, rapid development, and low-volume applications.

Possible materials include:

• Carbon-fiber-reinforced nylon
• Glass-fiber-reinforced polymers
• ABS
• PLA
• Other engineering-grade printing materials

Typical applications include:

• Prototype jigs
• Assembly alignment tools
• Custom soft jaws
• Conformal part nests
• End-of-arm tooling
• Low-load inspection fixtures

Their suitability depends on the required load, temperature, dimensional accuracy, chemical resistance, production volume, and expected service life. PLA and ABS are generally more suitable for design validation and light-duty applications than for high-load production fixtures.

Material Selection Guide

Material	Main Characteristics	Typical Applications	Relative Cost
Tool steel	High hardness, wear-resistant, heat-treatable	Locating pins, bushings, wear plates and inserts	High
Alloy steel	High strength, toughness and fatigue resistance	Clamping arms, shafts and high-load components	Moderate to high
Mild steel	Economical, weldable and widely available	Baseplates, frames and support structures	Low
6061-T6 aluminum	Lightweight, corrosion-resistant and easy to machine	Assembly jigs, inspection fixtures and soft jaws	Moderate
7075-T6 aluminum	Lightweight with higher mechanical strength	High-load lightweight components	High
Gray cast iron	Dimensionally stable with good vibration damping	Heavy machining bases and tombstone fixtures	Moderate to high
POM/acetal	Low friction, machinable and non-marring	Part nests, guides and delicate-part supports	Moderate
Nylon/UHMW-PE	Impact- and abrasion-resistant	Wear strips, guides and protective supports	Moderate
3D-printed polymers	Fast customization and design flexibility	Prototypes and light-duty, low-volume jigs	Low to moderate

Why One Fixture May Require Multiple Materials

A well-designed fixture often combines several materials rather than relying on a single material throughout the entire structure.

For example:

• Mild steel may be used for the base and welded frame.
• Hardened tool steel may be used for locating pins and wear surfaces.
• Aluminum may be selected for movable sections that require lower weight.
• POM or UHMW-PE may be used at contact points to prevent scratches.
• Replaceable hardened inserts may be installed in areas subject to repeated wear.

This approach helps balance accuracy, durability, weight, manufacturing time, maintenance, and cost.

Heat Treatment and Surface Finishing

Material selection alone does not determine fixture performance. Heat treatment and surface finishing can also affect wear resistance, corrosion resistance, dimensional stability, and service life.

Depending on the application, possible processes include:

• Through hardening
• Case hardening
• Nitriding
• Precision grinding after heat treatment
• Black oxide coating
• Electroless nickel plating
• Hard anodizing
• Stress relieving for welded structures

These processes should be specified according to the fixture’s operating conditions rather than applied as a standard requirement to every component.

How to Select the Right Material

Before selecting materials for a custom jig or fixture, the following factors should be evaluated:

• Workpiece material, hardness, and surface condition
• Required positioning and repeatability accuracy
• Expected production volume and service life
• Static, dynamic, and impact loads
• Frequency of loading and unloading
• Wear at locating, guiding, and clamping points
• Fixture weight and changeover requirements
• Exposure to cutting fluids, chemicals, heat, or moisture
• Maintenance and replacement of wear components
• Manufacturing budget and delivery schedule

A fixture designed for prototype production may require a very different material strategy from one intended for continuous mass production.

Custom Jig and Fixture Solutions from TM International

TM International provides custom jig and fixture solutions based on customers’ workpieces, manufacturing processes, production volumes, and accuracy requirements.

Our solutions may include:

• Assembly jigs and fixtures
• Machining and workholding fixtures
• Inspection and checking fixtures
• Welding fixtures
• Positioning and clamping mechanisms
• Custom nests and soft jaws
• Fixtures integrated with automated equipment
• Replaceable wear parts and locating components

We evaluate the complete application instead of selecting materials based on strength alone. By combining suitable structural materials, wear-resistant components, protective contact surfaces, heat treatments, and surface finishes, we help customers achieve a practical balance between precision, durability, maintainability, and cost.

To evaluate a custom jig or fixture project, customers may provide product drawings, 3D CAD files, physical samples, production requirements, and information about the intended manufacturing process.