Compression Limiters

Metal Compression Limiters provide and maintain joint integrity of a bolted plastic assembly. They are designed to protect the plastic components of an assembly from the compressive loads generated when a bolt is tightened to its recommended value, thereby ensuring that the joint remains intact throughout the life of the product. SPIROL’s Compression Limiters have been designed for easy installation, and provide excellent retention and anti-rotation.

SPIROL offers a comprehensive line of split seam, molded in, oval and solid wall designs to accommodate different compressive loads, positional tolerances and installation methods for bolts ranging in size from M4 to M10 and #8 to 3/8”.

split seam compression limiters
Split Seam Compression Limiters
Split Seam Compression Limiters are produced with flexible diameters to compensate for wide hole tolerances, yet the gap is designed to be less than the material thickness, therefore they will not interlock in the free state. The spring force generated during installation provides self-retention of all Split Seam Compression Limiters in the assembly. SPIROL offers several different Split Seam Limiters to accommodate varying application requirements.

Series CL200 Split Seam (Round): The Series CL200 Compression Limiter is produced from high carbon steel and intended for post-mold installation, and is rated for use up to ISO Class 8.8 / Grade 5 bolts. If the application requires it, the CL200 can be heat treated (made to order) for use up to ISO Class 12.9 / Grade 8 bolts. When applications can be designed around the Series CL200 standard range, this series offers the lowest total installed cost.

Series CL220 Split Seam (Round – Extra Clearance): Similar to the Series CL200 Compression Limiter, the CL220 has slightly different dimensions to provide additional 0.5mm clearance to the inner diameter and to accommodate ArmorGalv®, a zinc alloy thermal diffusion coating that provides up to 1000+ hours of salt spray protection for highly corrosive applications.

Series CL350 Split Seam (Heavy Wall): Similar to the Series CL200 Compression Limiter, the CL350 was designed with a thicker wall for increased bearing surface when clamped against soft mating materials. Generous bolt clearance also aids in positional alignment when multiple Compression Limiters are used in an assembly. The CL350 is rated for use up to ISO Class 10.9 bolts.

Series CL400 Oval Split Seam: Produced from high carbon steel, the oval Series CL400 accommodates 2.25mm extra clearance on one axis, providing additional flexibility over round Compression Limiters for centerline and stack-up tolerancing. Similar to the CL200 and CL350, this split-seam oval Limiter is formed, and it is spring tension that provides positive retention in the hole. The roll-forming manufacturing method yields substantial cost savings over machined products with similar features and characteristics. The CL400 is rated for use up to ISO Class 8.8 bolts.
molded-in compression limiters
Molded-In Compression Limiters (Butted-Seam)
SPIROL offers two different styles of roll formed Compression Limiters designed to be molded into the assembly. The roll forming process typically offers significant cost advantages over products that are produced by machining. Both the CL500 Round and CL460 Oval Molded-In Compression Limiter have a butted seam to prevent plastic from entering into the inner diameter during the molding process.

Series CL460 Oval Molded-In: The CL460 Series is similar to the Series CL400 Oval Split Seam, but produced with a butted-seam so as to prevent plastic from entering the inner diameter during the molding process. This series also accommodates 2.25mm extra clearance on one axis. The CL460 is rated for use up to ISO Class 8.8 bolts.

Series CL500 Molded-In (Round): The Series CL500 is produced from low carbon steel with a butted seam to prevent plastic from entering the inner diameter of the Compression Limiter during the molding process. This also provides an anti-rotation feature once in the assembly. The radial grooves provide axial retention. The CL500 is rated for use up to ISO Class 8.8 / Grade 5 bolts.
solid wall compression limiters
Solid Wall/Knurled Compression Limiters (Mold-In & Press-In)
SPIROL’s Solid Wall Compression Limiters can be either pressed in or molded into the assembly. SPIROL precision machines the Solid Wall Compression Limiters from aluminum and brass with knurls around the outer diameter for reliable retention within the plastic hole.

Series CL600 Aluminum: The Series CL600 is machined from 2024 aluminum as this grade provides the best combination of strength, corrosion resistance, machineability and cost. Additional advantages of aluminum are that it is lightweight (1/3 the weight of brass), it is 40% stronger than brass, and it is lead free. These Limiters can be molded in or pressed into the assembly. The precision machined ID tolerance allows proper seating on the core pin when molding into the assembly. When pressed into the assembly, they are designed with a pilot that allows the part to stand freely in the hole prior to completing the installation. Once installed, the knurl provides excellent retention within the hole. The CL600 is rated for use up to ISO Class 10.9 / Grade 8 bolts.

Series CL601 Headed Aluminum: The CL601 headed aluminum Compression Limiter is the same as the CL600, with the addition of a head. The head provides extra bearing surface on the mating component when a flanged bolt or a washer is not used.

Series CL800 Brass: The Series CL800 is machined from 360 brass. Similar to the CL600, the CL800 can be molded in or pressed into an assembly. The applications for SPIROL’s brass and aluminum Compression Limiters are very similar, however to accommodate the same class/grade bolt, the brass Limiters have a larger wall thickness due to the material’s lower yield strength. While this increases the size and weight of the Limiter as compared to the CL600, the thicker wall does provide more bearing surface for the mating component. The most common reason a designer may choose the CL800 is for those applications that require a shift away from aluminum on the galvanic series chart to make the Limiter more noble. The CL800 is rated for use up to ISO Class 10.9 / Grade 8 bolts.

Series CL801 Headed Brass: The CL801 headed brass Compression Limiters are the same as the CL800 with the addition of a head. Similar to the CL601, the head provides extra bearing surface on the mating component when a flanged bolt or a washer is not used.

Additional Information

Read How to Ensure Bolted Joint Integrity When Using a Compression Limiter in a Plastic Assembly and other White Papers on Compression Limiters.

Review our Application Stories for how SPIROL Engineers and Products have helped provide quality and cost saving solutions for fastening and joining problems.

SPIROL designs and builds Compression Limiter Installation Equipment to install Compression Limiters into your molded plastic assemblies.

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