Toolholding can have a significant influence on cutting quality, tool life and the overall performance of a CNC router.
When problems such as poor edge finish, excessive noise, vibration or premature cutter wear occur, attention naturally turns to the cutting tool. However, the condition and accuracy of the tool holder can also play an important part.
For high-speed CNC routing applications, shrink fit tool holders provide a precise and rigid alternative to conventional collet systems.
What Is a Shrink Fit Tool Holder?
A shrink fit holder uses controlled heating to expand the bore of the tool holder. The cutting tool is inserted while the holder is expanded and, as it cools, the holder contracts firmly around the tool shank.
This creates a strong, uniform connection between the tool and holder without the collet, nut and other moving components found in a conventional collet chuck.
The result is a compact toolholding system with high clamping force and very good concentricity.
Improved Concentricity and Run-Out
One of the main advantages of shrink fit tooling is accurate concentricity.
The closer the cutting tool runs to the true centreline of the spindle, the more evenly the cutting edges share the workload. Excessive run-out can result in one cutting edge doing considerably more work than the others, contributing to uneven wear, poorer surface finish and reduced tool life.
Modern high-quality shrink fit holders can achieve run-out figures around 0.003 mm, depending on the holder and application.
For PCD and solid carbide router cutters operating at high spindle speeds, maintaining accurate concentricity can therefore be particularly important.
Rigidity and Clamping Force
Shrink fit holders grip the cutter shank around its circumference, producing high clamping force without the mechanical components of a conventional collet system.
This provides a rigid connection between the cutter and holder and helps resist unwanted movement during machining.
For CNC routing applications involving profiling, grooving, trimming and production machining, good toolholding rigidity can contribute to consistent cutting performance and improved component finish.
Balance at High Spindle Speeds
CNC router cutters frequently operate at high rotational speeds.
Because shrink fit holders have relatively few components and are rotationally symmetrical, they can provide excellent balance and repeatability. HAIMER, for example, specifies high balance accuracy and repeatability as one of the principal advantages of its shrink fit systems.
Good balance can help reduce vibration transmitted through the cutting tool and spindle, particularly during prolonged production machining.
Can Shrink Fit Tooling Improve Tool Life?
Accurate toolholding cannot compensate for the wrong cutter geometry, unsuitable cutting material or incorrect machining parameters.
However, reducing run-out, vibration and uneven cutting loads can help a cutter operate closer to its intended conditions.
This can contribute to more even cutting-edge wear and may extend the useful service life of PCD, TCT and solid carbide tooling.
For this reason, when investigating unexpectedly short cutter life, the condition of the tool holder and spindle should be considered alongside the cutter itself.
Shrink Fit Tooling and Cutter Servicing
Prima Tooling can supply and service CNC router tooling used with shrink fit holders.
Where appropriate, cutters can be removed from the holder for inspection and servicing before being refitted, allowing the cutting tool and toolholding arrangement to be considered together.
This can be particularly useful with PCD router cutters, where accurate positioning and concentricity are important after sharpening or erosion.
Is Shrink Fit Right for Every Application?
Not necessarily.
Conventional precision collets remain suitable for many CNC routing applications and provide greater flexibility where different shank diameters are regularly used with the same holder.
Shrink fit systems are particularly attractive where priorities include:
- high spindle speeds;
- accurate concentricity;
- high rigidity;
- repeatable cutter positioning;
- reduced toolholder components; and
- consistent production machining.
The best toolholding method depends on the machine, cutter, material and production requirements.
Need Advice on CNC Router Tooling?
Prima Tooling manufactures and services PCD, TCT and solid carbide CNC router cutters for woodworking, panel processing, plastics, composites and production machining.
If you are experiencing poor cutter life, vibration, inconsistent finish or other tooling problems, we can look at the cutter design and application together with the toolholding arrangement.
Contact Prima Tooling to discuss your CNC router tooling application.