What’s a Jacobs cone?

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The Jacobs Taper is a type of machine taper used to secure tools in drill presses, lathes, and milling machines. It relies on friction and pressure for a secure grip and is an economical alternative to conventional chucks. Other members of the machine taper family include the Morse taper and Brown and Sharpe taper, with different sizes graded according to their taper profiles. The Jacobs Taper is commonly used in light load applications and is still popular even on modern CNC machines.

The term Jacobs Taper refers to one of a family of tapered machine tool shafts used to lock tools in place in drill presses, lathes, and milling machines. This group or family is collectively known as a machine taper and offers an economical and efficient alternative to conventional jaw chucks. The machine taper has been used since the first hand drills, milling machines and lathes and is still used as a reliable tool mounting system on modern numerically controlled (CNC) machines. Unlike conventional chucks which rely on the pressure exerted by three or more jaws to secure a bit or tool, the machine taper simply relies on friction across its surface and pressure against the work piece to hold it securely in place .

The different members of the machine taper family all work on the same basic principle. The tool shaft is tapered and is simply inserted into a similar profile socket in the machine head or spindle. The friction between the two mating surfaces and the pressure exerted by the workpiece hold the tool firmly in place. This simple system produces remarkable torque transmission and a very secure grip on the tool. These tool shafts and their corresponding mandrels typically have a slot running through them allowing for the use of a wedge to remove the tool when the job is complete.

Other variations in the machine taper family include the Morse taper and the Brown and Sharpe taper. These machine taper assemblies all have a number of different sizes graded according to their taper profiles defined by three basic dimensions. The first is the diameter of the cone at its wide end or major diameter, the second is the diameter at its narrow end or minor diameter, and the third is the axial length between the two. Jacobs Taper is generally represented by ten different sizes, all typically used in light load applications such as drill presses.

Jacobs Taper chucks are much cheaper to manufacture than conventional jaw types and tools can be changed much more quickly using this system. The Jacobs Taper and its family counterparts have been in use for many years and are still popular tool clamping options even on modern CNC machines. The Jacobs Taper tool chuck and shaft system is most commonly found on larger commercial drill presses, although smaller DIY (DIY and hob machines) are available with the locking system.




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