Making Sure Toolholders Stack Up for Long-reach Applications

by | Mar 1, 2024

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Engineers continue to design increasingly, intricate and complex parts in an effort to combine multiple parts into one component, thus eliminating secondary assembly processes. In many cases, shops producing those parts are faced with long-reach machining applications to cut deep cavities and other difficult-to-reach part features.

While it is feasible to keep some dedicated long-reach holders on hand, it is virtually impossible to anticipate the needed lengths of every application and much too costly to carry a complete inventory of dedicated long-reach holders. A more practical alternative is stacking your existing standard toolholders with extensions.

Solid fixturing and tool rigidity are the keys to successful long-reach machining. REGO-FIX powRgrip (PG) toolholders, collets and clamping units allow you to stack toolholders and extensions for the precise reach required for almost any application without investing in a cabinet full of dedicated tool extensions.

However, what shops need to keep in mind is that extended-tool and long-reach machining requires the tool cutting edges to engage at a considerable length from the toolholder and machine spindle. As a result, it’s not uncommon to encounter unwanted vibration, tool deflection and runout during the machining process. In addition to decreased accuracy, excessive runout, deflection and chatter can cause unacceptable surface finishes, undue tool wear, scrapped parts and even damage to the machine.

With a total system indicated runout (TIR) of ⋜ 3μm at 3 X D, powRgrip holders provide tighter tool holding for finer finishes while providing easier setups even in difficult applications. The system uses press-fit technology to apply up to nine tons of clamping pressure for an industry-leading 1,100 Nm clamping torque rating in 10 seconds or less.

With powRgrip, stacking is a straightforward process. After a thorough cleaning of all components, stacking can begin. As an example, a PG 25 toolholder fitted with a 20mm PG collet can be paired with a PG 20mm, 120mm extension and stacked using the powRgrip clamping unit. When that unit is pressed in approximately seven to 10 seconds, the extension can be fitted with a PG 10 collet and cutting tool and then set with the clamping unit. Technical bench tests have shown that stacking PG holders and extensions produces excellent results in terms of TIR – as good or better than dedicated long-reach tooling extensions.

With proper cleaning and the requisite care in assembly, stacking toolholding extensions will provide excellent repeatable results for those times when long-reach machining is necessary. When not used for extension stackups, the standard toolholder is available for other standard reach applications.  

To find out more about stacking extensions and toolholders or to get advice on how to stack REGO-FIX extensions and toolholders for a particular application, reach out to the REGO-FIX Technical Team for assistance. You can also email them at