Tooling & Workholding


The Toolholder is the essential connection between the machining center and the cutting tool. The toolholder fits into and is secured by the machining center’s spindle, and in turn secures the cutting tool such as a drill or end mill by clamping onto its shank. The taper of the toolholder matches the toolholder interface of the particular spindle. Toolholder tapers are often conical, including CAT and BT taper specifications. A different kind of taper, HSK, is not tapered at all, but instead includes a variety of flanges for securely locking the toolholder in place. Toolholders use different mechanisms for clamping the tool. A set screw can clamp onto a corresponding flat in the tool’s shank. Or, a collet can be compressed around the tool by tightening a nut that also surrounds the tool. More unusual clamping mechanisms include hydraulic toolholders, which compress a bladder of hydraulic fluid, as well as shrink fit toolholders, which clamp and release the tool by heating and cooling the toolholder’s metal to take advantage of thermal expansion and contraction. Other toolholder types use still other methods of clamping. Various clamping mechanisms aim to provide not just secure holding of the tool, but also tool concentricity to the centerline of the spindle that is accurate to a level of runout error appropriate to the tool and the machining process.

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Gripper for machine tool

Video: Parts Gripper Allows Machine To Act As Its Own Robot

This footage shows a workpiece gripper that enables a machine to load and unload workpieces on its own.

toolholder balancing machine

Video: Balancing Tools And Toolholders

This video provides both the argument and methodology for performing offline balancing of tool/toolholder assemblies for high speed machining centers.

Tungaloy DoMiniTurn toolholder

Expanded Toolholders for Swiss-Type Lathes

By: Edited by Jedd Cole
Tungaloy has expanded its DoMiniTurn line of external toolholders for Swiss-type lathes.

Indexing Technologies Sauter tool turret

Bi-Directional Rotation Speeds Lathe Tool Changes

By: Edited by Jedd Cole
The Sauter disc-type tool turret from Indexing Technologies is said to promote optimum performance on lathes, with a rigid, precise design that provides rapid indexing times.

OTT-Jakob Drawbar Features Intensified Spring Force

By: Lori Beckman (editor)
Advanced Machine & Engineering’s improved OTT-Jakob power drawbar for toolholding holds the cutting tool securely in the spindle taper with gripper fingers.

R-Zero runout adjustment system

Toolholder Incorporates Runout Adjustment System

By: Edited by Jedd Cole
NT Tool now offers the R-Zero runout adjustment system in its CTZ toolholders for large cutting-tool diameters.

Big-Plus toolholder

Testing Measures Impact of Toolholder Interface Rigidity

By: Peter Zelinski
Though Big-Plus and HSK share superficial similarities, they differ fundamentally in how they clamp the holder--a difference with important implications.

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