Introducing Two Powerful Additions to Unilock’s Most Popular 138 Series Workholding Chuck

Hoffman Estates, IL – The mid-size diameter and adaptability to custom fixture designs make the Unilock 138 series BIG KAISER’s best-selling round chuck workholding solution. Now come two new additions to the 138 series that make it an even more powerful and versatile solution for demanding workholding scenarios—the ESM 138 Turbo and the ERGO 138.

These new versions share the same fundamental body dimensions—diameter, bolt hole pattern, open port orientation, knob type, etc.—making them direct swaps for the original ESM 138 that operators have come to rely on. The ESM 138 Turbo and ERGO 138 also boast all of Unilock’s core features—including quick and easy setup and loading, self-guided top-side mounting, and the strength and consistency of zero-point clamping.

What’s Special about the ESM 138 Turbo
This improved version of the ESM 138 chuck has a closed back. This gives the chuck turbo capability, which more than doubles the spring-only clamping force, up to roughly 3,520 lbs, by simply connecting an air source to either the 1/8G turbo port on the OD, or the underside o-ring port. The sealed back also protects the chuck’s piston from contaminants, reducing maintenance while improving consistency.

Another new design feature appearing in the ESM 138 Turbo is slotted pin actuation. The dual-angled slot allows for faster and stronger transfer of clamping force upon closing, as well as a quicker, even release of the knob.

What’s Special about the ERGO 138
The ERGO 138 also has a sealed back, protecting the internal mechanics from contamination and making it turbo-capable. In another effort to help maintain clean operations, the back cover has an air blast port which cleans the knob upon entry. By connecting an air source, operators can clean the chuck and knob before locking it, ensuring firm and consistent positioning during loading/unloading and preserving the equipment. It’s ideal for fine-particle materials like cast iron.  

The ERGO 138 is 11mm shorter than the standard ESM 138, featuring a new body height of 28mm, providing more workable area. Rectangular clamping pins are substituted for standard round pins and now lock the knob more securely with a knee-type lock—reducing the chance of slippage. The inner contact ring has been expanded to Ø80mm, offering a larger contact surface area than the ESM 138’s Ø60mm. These features add improved characteristics, but do not affect the ability to exchange with original ESM 138 chucks on a 1-for-1 basis.

BIG KAISER Precision Tooling Inc. is a leader in high precision tooling systems and solutions. With brands including BIG Daishowa, KAISER, Speroni, Unilock, Sphinx and more, BIG KAISER’s line is focused on extreme accuracy and repeatability. BIG KAISER’s mission is to support North American manufacturers with products that are designed and manufactured to a superior standard. Guaranteed.