rates. On long-running jobs it is common to use a roughing tool on a different slide or turret station to remove the bulk of the material to reduce wear on the form tool. There are different types of form tools. Insert form tools are the most common for short- to medium-range jobs (50 to 20,000 pcs). Circular form tools are usually for longer jobs, since the tool wear can be ground off the tool tip many times as the tool is rotated in its holder. There is also a skiving tool that can be used for light finishing cuts. Form tools can be made of cobalt steel, carbide, or high-speed steel. Carbide requires additional care because it is very brittle and will chip if chatter occurs. A drawback when using form tools is that the feed into the work is usually slow, 0.0005" to 0.0012" per revolution depending on the width of the tool. Wide form tools create more heat and usually are problematic for chatter. Heat and chatter reduces tool life. Also, form tools wider than 2.5 times the smaller diameter of the part being turned have a greater risk of the part breaking off. When turning longer lengths, a support from the turret can be used to increase turning length from 2.5 times to 5 times the smallest diameter of the part being turned, and this also can help reduce chatter. Despite the drawbacks, the elimination of extra operations often makes using form tools the most efficient option. Toolholders By confining the expensive hard cutting tip to the part doing the actual cutting, the cost of tooling is reduced. The supporting tool holder can then be made from a tougher steel, which besides being cheaper is also usually better suited to the task, being less brittle than the cutting-edge materials. The tool holders may also be designed to introduce additional properties to the cutting action, such as: angular approach – direction of tool travel spring loading – deflection of the tool bit away from the material when excessive load is applied variable overhang – the tool bit may be extended or retracted as the job requires rigidity – the tool holder can be sized according to the work to be performed direct cutting fluid or coolant to the work area Note that since stiffness (rather than strength) is usually the design driver of a tool holder, the steel