Clamping devices, lubrification and filtration for drills with internal cooling
General information
In the industry for metal work tools, shorter processing times are always in demand. At the same time, the requirements to the manufacturing precision and process reliability are growing. To fulfill these requirements, the "machine tool (all types of drilling machines) – spindle – tool – tool holder" system must be perfectly adjusted.
The following requirements have to be taken into account:
- For the machine tool: High level of stiffness, vibration isolation of the foundations, lightweight design of the moving parts, high concentricity accuracy of the spindle, pull-in forces of the machine spindle, intelligent and quick machine controls
- For the tool holder: High concentricity and balanced, friction-locked tightening of the tool
- For the tool: High concentricity, excellent balance quality (geometry and shank design), long tool life (tool material, geometry, coating)
Tool Holders
Hydraulic expansion tool holder
These ensure the high concentricity during drilling.
Characteristics:
- Concentricity: 0.003 mm (.00012”) (measuring point at 2.5 x D)
- Max. speed: 50'000 rpm / balance rate (G 2.5 / 25000 1/min)
- Precise concentric clamping
- High torque transmission
- Maintenance-free (closed system)
- No wear in the clamping diameter
- Longer (up to 4 times) tool life
- Adjustable clamping force
- Short tool change time (without additional devices such as, shrink fit device)
Application:
- High-precision clamping of tools with cylindrical shaft
- Universal tool holder for drilling and milling (roughing and finishing). Advantageous in the case of HSC processing (milling, for example on a small CNC milling machine) due to its shock-absorbing.
Shrink fit tool holder - shrink fit tool holder according to DIN 69871
These guarantee highest concentricity with secure friction-fit connection and form an optimal connection between the tool and the holder.
Characteristics:
- Concentricity: ≤ 0.003 mm (.00012”)
- Max. speed: 40'000 rpm
- Absolutely secure friction-fit force transmission
- Adequate for shaft diameter of 4 mm (.157”) (3 mm (.118”) are conditionally possible).
- Transmittable torque 2 to 4 times higher compared to the hydraulic-tool holder and the high precision collet tool holder.
- Average tool change time (shrink fit device is necessary)
- Suitable for machining in narrow spaces and interfacing edges due to the small overall construction size and longer versions
Application:
- Optimal for HSC machining, in particular also for smallest drill bits
- For milling and drilling tools with cylindrical shaft
Collet tool holder systems (ER collet chucks) according to DIN 6499-A / optimized precision collets
These guarantee highest concentricity.
Characteristics:
- Concentricity: 0.003 mm (.00012”) possible
- Max. speed: 40'000 rpm
- Average tool change time (a torque wrench is necessary)
Application:
- Clamping of tools with a cylindrical shaft in high precision collet according to DIN 6499
- Universal tool holder for milling (roughing and finishing) and drilling.
Balance quality
The balance quality of the collet tool holder is specially critical in high speed machining processes. The best possible balance quality guarantees not only reduced vibrations of the tool but increases tool life, improves surface quality and above all, protects the spindle bearings.
Types of drilling machines
CrazyDrill Cool is used on various types of drilling machines, on CNC machines, automatic lathes or transfer machines (for example rotary transfer machine).
- Minimum speed 8’000 rpm (drill size diameter 0.75 mm / .030”)
- Minimum concentricity of spindle 5 µm (.00019")
Coolant / Filter, coolant pressure and quantity
For best results, Mikron Tool recommends the use of cutting oil as coolant fluid. Alternatively, emulsion of 8% or more with EP-Additives (Extreme-Pressure-Additives) can be used with good results as well.
Filter: Good filter quality is generally very important in drilling tools with through-tool cooling so that no dirt particles or chips reach the tool through the coolant supply, thus jeopardizing flow through the cooling channels. The following filter qualities must be adhered to especially in small diameters:
Twist drill types with diameter < 2 mm (.079”) filter quality ≤ 0.010 mm (.0004”)
Twist drill types with diameter < 3 mm (.118”) filter quality ≤ 0.020 mm (.0008”)
Twist drill types with diameter < 6 mm (.236”) filter quality ≤ 0.050 mm (.0020”)
Coolant pressure: In the CrazyDrill Cool twist drill types (drill with through-tool cooling, channels up to the drill tip) at least 25 bar of coolant pressure are needed with a drill diameter of 4.0 – 6.0 mm (.157” - .236”) to ensure a reliable drilling process. Higher pressures (see table) are needed for smaller drill size diameters. High pressure is generally better for the cooling and flushing effect. The shaft-integrated power chamber also supports the coolant flow in drill diameters under 3 mm (.118”).
