The world of workholding offers nearly as many solutions as there are workpieces, and often, there is no straightforward answer to what the correct solution might be. If you’ve made it to this guide, congratulations on taking the crucial first step: deciding on the type of chuck you need.
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Now that you’ve chosen a collet chuck, we’re here to help you find the right one. Thankfully, selecting the correct collet chuck is a relatively straightforward process. A detailed review of all the Chucks and their technical data would make this blog post rival the University Physics with Modern Physics 14th Edition in length but we will link all Collet Chucks for you to easily take a closer look.
The first step in selecting a collet chuck is distinguishing between rotating and non-rotating (stationary) work.
For stationary work, such as milling or drilling, there are two primary options:
CB-NRB Chuck: This hydraulically actuated, self-contained pullback design is ideal for non-rotating applications. The collet is drawn into the tapered seat when actuated, with part stops mounted inside the chuck body.
CB-NRD Chuck: A hydraulically actuated dead length collet chuck for stationary use. The sleeve moves forward under hydraulic pressure to clamp the collet, keeping the part securely in place.
If your process requires rotating work, it gets a little trickier, but don`t worry we will go through the list together.
The next step is taking a closer look at the Workpiece Type. If what you do is Shaft work, we have 2 more options for you:
CB-AG Chuck: This pullback design features a floating collet seat for machining shafts between centers. The compact design offers greater rigidity, and the floating seat can be locked to clamp parts on-center.
WSF Chuck: Ideal for machining shafts between centers, this chuck allows for complete machining of the shaft’s OD while securely clamping the end.
For bar work, the choice of chuck depends on the bar feed type:
If it’s a Servo Bar Feeder what you need is a Pull to Close Collet Chuck, the CB-NDR is the right choice for you:
CB-NDR Chuck: Designed for use with servo bar feeders, this patented dead length design prevents the bar from being pushed off the servo stop.
On the other hand, if you work with a Hydrostatic Bar Feed Type and the Feed length is not critical the Collet Chuck you need is the
CB-NB Chuck: For hydrostatic bar feeds where feed length isn’t critical, this chuck efficiently translates draw tube force into maximum clamping force.
For situations where feed length is critical:
CB-ND Chuck: Suitable for collet sizes 120mm and larger, the collet remains fixed in the Z-axis, avoiding any pullback effect on the bar stock.
CB-NX Chuck: This low-profile, dead length design features a reduced diameter nose for maximum tool clearance, ensuring no pullback effect during clamping.
For chucking work, if your setup includes a sub-spindle and requires a dead length chuck, consider:
CB-ND Chuck: Suitable for collet sizes 120mm and larger, the collet remains fixed in the Z-axis, avoiding any pullback effect on the bar stock.
CB-NX Chuck: This low-profile, dead length design features a reduced diameter nose for maximum tool clearance, ensuring no pullback effect during clamping.
Both chucks maintain the collet fixed in the Z-axis, preventing any pullback effect on the workpiece.
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For main spindle applications, where dead length chucks are needed, the above chucks are also ideal.
However, if you require a pullback collet chuck, especially for vertical spindles, the CB-NK Chuck is your go-to. This flexible design allows easy conversion from bar to chucking applications with the capability to mount end stops inside the chuck body.
Chucks are used to hold round shank tools. There are many styles of chucks, and chuck selection varies depending on:
In the table below, you can see a comparison between different styles of chucks, which can help you to make the best chuck selection.
High-precision hydraulic chuckShrink fitPower chuckER collet chuckWeldon Pull-outThe cylindrical shank is clamped evenly and is used for the best run-out accuracy for milling, drilling and reaming. With no flat or locking, it has torque and axial force limits before the shank moves in the holder.
The hydraulic membrane provides high clamping force and run-out accuracy. It is very simple to handle, without the need for separate equipment. Collets can be used, which reduces the number of chucks needed and allows coolant to be delivered through the tool (drilling) or through the collets (milling).
The bore of the chuck is slightly smaller than the shank diameter; the chuck is heated up to expand when changing the tool. Due to thermal expansion between the holder and the tool shank, shrink fit chucks are mainly used for solid carbide round tools. Heating equipment is needed to change tools and each chuck is for one shank diameter and coolant delivery only. This makes shrink fit best suited for production with a tool-setting room for tool changing.
Shrink fit offers good accessibility and high run-out precision, with medium to high clamping force.
The run-out accuracy and clamping force are not as good as with hydraulic or shrink fit chucks. However, the very good flexibility with collets makes the ER collet chuck an economic all-round chuck for drilling and light milling applications. The tool change can be handled at the machine with a fixture. Use a torque wrench to ensure that the chuck is not overtightened, which reduces accuracy and damages the chuck.
A shank with a flat is used for higher torque applications where torque security is more critical than run-out accuracy.
The drill adapter is suited for medium to large drilling operations. The flat runs all along the shank, as the drill has only compressive axial forces (pull-out is not a risk), but has an axial face contact with the adapter for best stability. The drill adapter differs from the Weldon adapter, in that the face of the adapter is ground and the shank is longer for best stability.
The Weldon or “milling” adapter was the traditional chuck used for milling applications. The short flats provide torque resistance and pull-out security. However, the downside with Weldon is the run-out accuracy, which is an important factor for milling tool performance. More often, this type of chuck is replaced with shrink fit or hydraulic.
The modular screw coupling interface provides many benefits for milling and boring. For smaller machines, removing the need for a chuck allows for shorter gauge lengths, which dramatically reduces vibration. For long overhangs, the shank material and shape can be optimized more easily compared to solid tools.
For milling, longer solid carbide tools are costly; when only the end is used, tool costs can be significantly reduced.
Used mainly for small and medium machine spindles (HSK40/50/63 – steep taper #30, 40 – C3/C4/C5/C6). All other chucks build length into the assembly. Reduce the gauge length to below three times the flange contact to reduce vibration and increase productivity.
The shank length is selected that provides the best stick-out length from the chuck. Steel is used up to 3 x D and solid carbide up to 8 x D.
The conical shape has a big impact on stability. Conical should always be used where clearance allows and for 5-axis machining. Replacing conical solid carbide end mills has a big impact on tooling costs. Conical shanks exist in cylindrical shanks as well as Coromant Capto® for steel.
Over three times the shank diameter, vibration is always an issue. Optimizing the stick-out length to the absolute minimum required makes a difference. The G undersized shanks are 0.3 mm (0.012 inch) smaller than the cutting diameter and used in combination with dedicated collets for hydraulic chucks, the shank length can easily be modified. Their application area is from 3-6 times the shank diameter.
The tap adapters are designed for tapping operations in machines equipped with automatic tool change. A construction for pull and pressure compensates for differences between spindle feed and thread pitch. Even micro differences between calculated feed and actual pitch of the tap can lead to extremely high thrust forces on the tap flanges and an increase in cutting pressure. When threading with a tap with a cylindrical square shank, it is important to use a tap adapter of the same size as the shank/square.
Synchronized tapping chucks, such as CoroChuck® 970, are based on a micro compensator, which aligns radial and axial deviations. Thrust forces are reduced on the tap flanks, which results in better surface quality and longer tool life. Synchronized tapping chucks use ER collets with a square drive. It is not recommended to use a collet without the square drive, due to the high torque that will make the tap rotate in the collet if the square drive is not used.
For quick change tap adapters, it is also important to use the right-sized tap adapter; otherwise, the risk of tap breakage is high and tolerance on the finished thread is poor.
To get the best result from machines that are not equipped for synchronized tapping, the following recommendations should be observed:
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