· DC collets have two opposing 30° angles that grip the tool shank. They are a very common and versatile collet type, known for good gripping force and high accuracy.

· Back Locking: This is the locking mechanism.

  · Instead of a nut on the front, this system is tightened from the back (the end that goes into the machine spindle).

  · A special wrench is inserted through the back of the chuck body to actuate an internal mechanism that squeezes the collet.

· Collet Chuck: This is the general category. It‘s a holder that uses a removable collet to clamp onto a cutting tool (like an end mill, drill, or reamer)

 

The "Back Locking" design is the key differentiator from common nut-style chucks like ER collet chucks.

1. Assembly: You insert the collet (e.g., a DC5 collet for a 5mm tool) and the cutting tool into the front of the chuck body.
2. Locking: A special L-shaped hex key is inserted into the back of the chuck. Turning this key engages an internal drawbar or mechanism.
3. Action: This internal mechanism pulls the collet back into a tapered seat inside the chuck, causing the collet to compress and grip the tool shank uniformly.
4. Unlocking: The same hex key is used in reverse to release the collet and tool.

 

The "Back Locking" design is the key differentiator from common nut-style chucks like ER collet chucks.

1. Assembly: You insert the collet (e.g., a DC5 collet for a 5mm tool) and the cutting tool into the front of the chuck body.
2. Locking: A special L-shaped hex key is inserted into the back of the chuck. Turning this key engages an internal drawbar or mechanism.
3. Action: This internal mechanism pulls the collet back into a tapered seat inside the chuck, causing the collet to compress and grip the tool shank uniformly.
4. Unlocking: The same hex key is used in reverse to release the collet and tool.

 

Feature BT40-DC Back Locking Chuck Common BT40-ER Collet Chuck
Locking Method From the back with a hex key. From the front with a nut and wrench.
Runout Accuracy Very High (often < 3µm) Good (typically 5-10µm for quality chucks)
Gripping Force Very High High
Ease of Use Slightly slower, requires special key. Very fast and simple.
Profile Slim, no front nut. Bulky due to the front nut.
Cost Generally more expensive. Generally more affordable.