In the world of metalworking, toolholders often provide the connection between the CNC and the cutting tool. Producing the necessary synergy for optimal clamping when machining materials. Here, we’ll talk about some types of CNC toolholders. And discuss the basics you should know before choosing the right toolholder for your operation.
Balance of Precision, Rigidity, and Versatility in CNC Toolholders
Because the toolholder holds the tool securely and transmits power from the CNC spindle to the tool, you always need to ensure that your tool is balanced. The balance of the toolholder ensures that everything remains in the correct position. Toolholders have their own level of balance, depending on the style of adapter.
Some toolholders are designed to be balanced, while others are not. The degree of balance is measured in grams. The better the toolholder is balanced, the more consistent the wear on the tool. This results in better surface finish and longer tool life.
To maintain balance, your toolholder should have:
- Precision: The tool should consistently produce workpieces with minimal deviation from the expected dimensions. Toolholders affect factors such as radial runout, concentricity and axial alignment.
- Rigidity: Rigid toolholders provide stability during cutting, preventing tool deflection and chatter, and preventing damage to the tool and workpiece. With high-quality toolholders, vibrations can be absorbed and heavy machining forces will not damage the tool.
- Versatility: Toolholders with the ability to quickly change a variety of cutting tools can increase productivity and reduce setup time. When adapters and chucks can be easily changed, they do not require custom tool setups during complex machining processes.
Toolholder Tips You Should Know
Torque: One of the main functions of a toolholder is to transmit torque from the CNC spindle to the tool. Optimizing torque transmission can minimize energy losses during machining and maximize machining power.
Radial runout: Also known as concentricity or total indicated runout (TIR), radial runout is critical to achieving precise machining results. Make sure your tools are aligned to minimize their deviation from the axis. Damping Toolholders with damping functions absorb and reduce vibrations during cutting, thereby reducing chatter and improving surface finish. Unpredictable vibrations can lead to poor surface finishes and damage your cutting tools.
High-speed capabilities: Specially designed toolholders can handle high speeds without compromising stability, allowing for faster cutting speeds without compromising accuracy. They ensure reliable performance at high speeds.
Types of CNC Tool Holders
Improving machining performance by increasing feeds and speeds can help increase productivity. But choosing the right toolholder is critical to your success. When choosing the right toolholder, consider factors such as machine spindle type, cutting application, horsepower, thrust, material, and required cutting parameters.
Some standard and advanced toolholders include:
Hydraulic toolholders: Hydraulic chucks are particularly effective in damping vibrations and absorbing cutting forces during machining by hydraulically clamping the tool securely. Hydraulic chucks are ideal for precision work and high-speed operations. They can handle roughing and finishing tasks with excellence. There are also many damped toolholders on the market, which provide the highest precision, clamping force, and provide excellent damping qualities. This technology minimizes runout, extends tool life and improves cutting performance. Shorter protrusion lengths and thicker front wall cross-sections enable high rigidity. They can also be used in long-reach applications and narrow operating conditions.
Shrink-fit toolholders: Shrink-fit toolholders offer high clamping force, low tool deflection and stability at longer tool lengths, providing good surface finish in high-feed milling applications. They are designed to clamp cutting tools through a process called thermal expansion. When the toolholder cools and shrinks after heating, it creates a strong clamping force on the tool.
ER chucks: ER chucks are widely used to clamp round shank cutting tools. Known for their good clamping force and flexibility, they are suitable for light to medium-duty drilling, milling and tapping. They are available in different sizes and can be identified by codes such as ER32 or ER40, which correspond to their system sizes.
Whether you choose a traditional toolholder or a shrink-fit toolholder, hydraulic toolholder, etc., if machining accuracy is required, it is recommended to invest in some good quality toolholders.
Need to Know About Machine Tool Spindle
The spindle is an essential component of any machining center. It holds the toolholder and rotates the cutting tool at high speeds. Compatibility with the machine spindle and specifications is critical when selecting a toolholder.
There are several types of spindle connections, the most common being:
Tapered connections (such as CAT and BT types) are common connection types that use flanges and retaining knobs for a secure connection. CAT (V-flange) is more popular in the United States, while BT (MAS) is widely used in Asia and Europe. These connections have high rigidity and are common in milling and machining centers.
Cone-to-taper connection types (such as CVKV) are similar to CAT and BT types, but are more rigid and run faster. They have a taper for better contact with the spindle surface to maintain accuracy.
HSK (Hollow Shaft Taper) offers an advanced spindle connection system designed for high-speed machining and complex milling operations. It features a hollow shaft and a set of clamping segments that provide excellent stability, balance, and concentricity.
CNC Toolholder Connections
Tool-end connections refer to the interface between the tool and the toolholder. The two most common types are:
Straight Toolholders: These are designed with a uniform diameter across their entire length and are typically used with a collet system. They are suitable for light to medium-duty applications and are often used with drill bits, reamers, and taps.
Weldon CNC Toolholders: These are designed with a flat surface on one side of the shank for better grip and enhanced torque transfer. They are widely used on milling cutters and other end mills to provide stability during heavy-duty cutting tasks.
