One article to understand the types and applications of CNC toolholders

As an important “bridge” connecting machine tools and cutting tools, the tool holder is related to the quality of processing accuracy, tool life, processing efficiency, etc., and ultimately affects the processing quality and processing cost.

Therefore, it is very important to correctly choose a suitable tool holder.

Since the requirements of various processing are different, tool holders with different clamping methods correspond to them. Here, the general characteristics of various tool holders are briefly introduced.

1. Spring tool holder

Working principle: The tapered spring collet is gradually contracted during the axial movement (locking) to clamp the cutting tool.

Scope of application: drill bits, reamers, finishing end mills, etc.

Features: large clamping range; good versatility; high precision (only for some manufacturers).

Key points: Whether the spring collet can shrink perfectly and evenly is one of the key factors determining the runout accuracy; the bearing nut can greatly reduce the torque on the collet during locking.

The runout accuracy level of the spring collet at 4D represents within 20μm. Ordinary ER collet within 10μm. Precision ER collet within 5μm. Ultra-precision collet of a few manufacturers within 3μm. Top-level high-precision NBC collet

2. Hydraulic toolholder

Working principle: Use hydraulic pressure to shrink the inner diameter of the toolholder to clamp the cutting tool.

Scope of application: High-precision processing of end mills, carbide drills, diamond reamers, etc.

Features: Easy to operate, only one T-type wrench is needed to tighten, which is the simplest clamping method among all toolholders; stable accuracy, the tightening force does not directly act on the clamping part, even new operators can clamp stably; completely waterproof and dustproof; good anti-interference performance, some slender hydraulic toolholders on the market are comparable to the anti-interference performance of heat shrink toolholders.

3. Heat shrink toolholder

Working principle: Use the difference in thermal expansion coefficient between the toolholder and the cutting tool to clamp the cutting tool.

Scope of application: Processing occasions with high interference conditions.

Features: Good anti-interference performance; small clamping range, can only clamp cutting tools of one size; good initial runout accuracy (decreases rapidly with the increase in heating times); requires special heating and cooling devices, poor safety, and high requirements for operators.

Fourth, strong milling cutter handle

Working principle: The handle body is compressed by the nut to clamp the cutting tool.

Scope of application: Heavy cutting of end mills.

Features: High rigidity; Strong clamping force, the largest clamping force among all clamping handles; Poor anti-interference performance; (Recently, some manufacturers have launched strong milling cutter handles with a nut outer diameter of only 32mm) The runout accuracy is average, generally below 0.02mm, but some manufacturers have achieved 5~10μm.

Key points: Whether the elastic deformation is uniform and whether the shrinkage is sufficient. (The thickened chuck design can increase rigidity and withstand heavy cutting of end mills.)

Typical case: The strong milling cutter handle made by Daishowa Co., Ltd. in Japan adopts a very unique slit structure, which can make the chuck deform evenly, with strong clamping force and stable runout accuracy.

Five, side-fixed chuck

Working principle: As the name suggests, the cutting tool is locked by the side fixing screw.

Scope of application: used for rough processing of drills and milling cutters with flattened shanks.

Features: simple structure, strong clamping force; but poor accuracy and versatility.