Bosch: Clutch Types and Their Benefits
Bosch Automatic Shut-Off Clutch Features
Our shut-off clutch is designed to minimize user influence on the fastening process. Bosch shut-off clutches are among the worlds’ best in providing excellent repeatability & accuracy; they are ideal for fastening applications where torque accuracy is critical. Our repeatability rivals that of some DC-feedback tools costing thousands more than comparable Bosch air-driven tools.
A Proven Performer
The patented Bosch shut-off clutch has been used in hundreds of applications over the years and is a proven performer in many real-world production environments. Our patented ball & detent design is virtually wear-free; the clutch will last for millions of fastening cycles before it must be replaced. The tool runs until the shut-off clutch disables the air motor by closing the air inlet valve. The tool runs again when the operator releases the trigger or moves to the next fastener (some push start models do not require a trigger).
Precise, Accurate Shut-Off
Our Shut-off clutch ensures high torque repeatability and accuracy. Whether in a hard joint application of 30 degrees or a soft joint of 720 degrees, the clutch guarantees an extremely low mean value offset and consistent torque. Clutch quality conforms to ISO 5393 requirements.
Precise and Stable Under Load
Bosch quality testing for our shut-off clutch is extremely rigorous. Each version of air tool with a shutoff clutch must survive a one million (1,000,000) cycle test under load without failure or excessive adjustment during development. All ball & detent-type Bosch clutches (shut-off, cushion & S–plus) provide 15% greater torque in reverse for removing fasteners. Precise adjustment is done with a special wrench. Modular design means fewer parts can cover several ranges & types of clutch.
Ratcheting Cushion Clutch Features
The Bosch ratcheting cushion clutch shares many parts with the shut-off clutch; in principle, it works exactly the same as our shut-off clutch, but does not turn off the air motor of the tool when desired torque is reached. As a result, the tool ratchets on a cushion of clutch balls until the operator releases the trigger. It’s great for soft joints or prevailing torque fasteners such as wood, sheet metal and self-tapping screws and provides good torque accuracy. The user can have a slight influence on final torque by allowing the clutch to ratchet for a longer period of time.
S-Plus Combination Clutch Features
The Bosch S-Plus combo clutch is unique in the fastening industry. It is ideal for prevailing torque fasteners where start torque exceeds seat torque, such as a self-tapping screw. It combines the function of a shut-off and ratcheting cushion clutch into one clutch; this is done by installing a bypass valve on a standard shut-off clutch to allow the air motor to run when desired. An example would be a self-tapping screw in thick plastic: the initial torque needed to get the screw started is higher than desired final seat torque. The user can bypass the shut-off clutch and allow it to perform as a ratcheting cushion type until the threads are cut. Once the screw begins to spin freely, the bypass lever is released and the clutch becomes a shut-off type!
T-Grip Impulse Wrench (With Shut-Off Function) Features
Bosch T-Grip impulse wrenches offer excellent performance/weight ratios, low reaction speed and low noise. A Polyamide housing makes the tool strong and light. A centrifugal shut-off mechanism shuts off the tool when desired torque is reached. These tools provide a more accurate alternative to impact wrenches and a higher-rpm alternative to shut-off clutch tools.
Bosch impulse wrenches are especially compact thanks to a patented impulse method of piston compression in a bath of hydraulic oil. The impulse mechanism from Bosch has only three major moving parts which increase longevity and resist higher loads than sleeve valve or vane type impulse mechanisms. Bosch impulse wrenches require no special tools, vacuums or syringes for service, and a typical oil change can be done in less than 10 minutes!
Impact Wrenches
Bosch production impact wrenches are ideal for large fasteners with low torque accuracy and high rpm demands. They tighten the fastener using rotary impact pulses in a pin-type impact unit. High-alloy materials insure long life and minimal service demand.
Torque accuracy is dependent on finding the right driver for the desired fastener and type of joint (hard or soft).
The perfect torque for a fastener and joint is dependent on the type of application. Joints are referred to as “hard" or “soft”, depending on the material being secured. Hard joints are typically very repeatable; soft joints will produce a lower acceptable torque value for the same fastener since the joint crushes more as it is tightened. Torque deviation rises in soft joints. It’s impossible to account for all fastening scenarios in a catalog; there are too many possible variables in the fastening process. Always verify tool application to a joint with an actual test using torque measuring equipment and the actual joint. This chart gives an overview of the potential benefits & torque accuracy of each type of driver/clutch with various fastening applications.
Clutch Torque Accuracy/Repeatability