Understanding Gasket Tolerances

Gaskets have tolerances on their key attributes. The tolerances are dictated by a combination of material characteristics and manufacturing processes. If you want your new gasket to seal properly, it's important to understand how these tolerances work and if they are within your parameters.

Key Gasket Attributes

Dimensions are often critical for sealing devices. However, unless a gasket goes in a channel, the outer dimensions aren’t usually critical to success. What does matter, though, are the bolt hole positions, bolt hole diameter, and the inner shape. The inner shape of the gasket should not impede or intrude into the flow.

Gasket Material Thickness

Tolerances are dependent on material type (PTFE, Silicone, Neoprene, EPDM, etc.) and industry standards for your specific application.

Manufacturing Process Tolerances

Gasket sheet material can be cut in many ways. Perhaps the four most popular methods are

Die cutting
Oscillating knife, also known as flash cutting
Water jet
By hand

The most repeatable, but least accurate, is die cutting. This is typically used for large quantities of gaskets. Both flash cutting and water jet cutting have high accuracy with regards to dimensional cutting; however, these methods are slower than die cutting, since only one gasket is cut at a time.

Tolerances explained

Die cutting. A laser-cut block can usually hold +/- 0.015” (+/-0.381mm) although this tolerance increases with tool sizes. The larger the tool, typically the less precise. Harder material may help with cut accuracy since softer, thicker material deforms more during cutting. Die-cut gaskets are very consistent, with the first piece identical to the last
Water jet. Accuracy is set by table motion and the precision of the gantry. In general, it is around +/-0.007”
Flash cutting/oscillating knife. Machine repeatability is claimed as 0.010mm but in practice +/-0.003” (+/-0.076mm) is more typical.

Gallagher Fluid Seals Flash Cutters

Flash cutting is dieless, automated process, utilizing a reciprocating knife cutting system guided by a CNC machine to create custom parts in a matter of minutes. Patterns can be uploaded directly from CAD programs to begin immediate production on your project.

With multiple flash cutters and flat bed die cutting, Gallagher Fluid Seals can help with all your gasketing needs.