Collet System Keeps Cool Under Pressure
Coolant-through tooling is becoming increasingly popular as manufacturers continue to search for new ways to maintain the tight tolerances, high accuracies and smooth surface finishes required for many of today’s jobs. While coolant-through spindles are now a standard feature on many new machines, the machines and tools themselves represent only part of the equation. The interface between the spindle and the tool—a properly sealed toolholder—is just as important.
Coolant-through tooling is becoming increasingly popular as manufacturers continue to search for new ways to maintain the tight tolerances, high accuracies and smooth surface finishes required for many of today’s jobs. While coolant-through spindles are now a standard feature on many new machines, the machines and tools themselves represent only part of the equation. The interface between the spindle and the tool—a properly sealed toolholder—is just as important. Users of collet systems in particular need a reliable method to keep coolant from spraying through gaps between the holder, collet and nut or through the slits in the collet itself.
To address this concern, toolholding system manufacturer Rego-Fix has developed a metallically sealed collet that keeps through-tool coolant on target and eliminates the need for accessories such as sealing disks and plugs. By providing a tight seal between the toolholder and the tool, the collet helps users ensure that coolant is applied directly to the cutting area to provide much-needed lubrication, chip evacuation and temperature control. These benefits are especially important in applications such as deep-hole drilling in which impacted chips can cause excessive tool wear and degrade hole quality.
Like most collet designs, the body is constructed with open slots that allow it to expand or contract to clamp a given range of tool diameters. Rather than running through the entire length of the body, however, slots in the metallic sealed collet extend only about half the distance to the clamped tool. Although this configuration limits clamping range, it also provides a barrier at the front of the collet so coolant can flow only where it is intended—through the tool itself.
One of the collet’s primary advantages over other sealing methods is that it is able to withstand the force of coolant exerted at pressures as high as 2,000 psi. This is important because coolant-through applications require high pressure to provide adequate chip removal at the tool point. In contrast, common sealing devices such as plugs constructed of rubber or silicon can be inconsistent in high-pressure applications because aggressive coolant flow can blow them out of collet slots.
An added benefit is that the collet is designed for universal use—that is, it is compatible with any standard or friction-bearing nut. Using a collet that is sealed by design can help shops keep inventory levels low because they have no need to purchase sealing disks, specific coolant nuts or other accessories. In addition, the metallic sealed collet is suited for applications that require high runout accuracy. Able to achieve 0.2-inch TIR, it is available in standard and metric sizes ranging from 0.125 inch to 0.75 inch and 3 mm to 20 mm.
A seemingly small amount of runout can still be too large for the tool. Reduce this runout, and tool life or productivity may dramatically increase.
Companies concerned about strict quality requirements regularly check toolholder tapers for wear or inaccuracy because these conditions can jeopardize the results of a critical operation. However, a shop can check tapers quickly and reliably with air gages. These devices can be used effectively without special operator training. For measuring taper in a production environment, few other methods can match the speed and performance of air, as multiple-circuit air jets can be placed in very small taper gages.
Hummingbird takes on machining work that is too small for most shops to handle. In fact, Hummingbird tries not to handle it either. To accurately machine the tiniest parts, this shop relies on processes that are as hands-off as possible.