External turning

External turning operations machines the outer diameter of the workpiece. Since external turning is one of the most well-known and commonly used process, demands on chip control, process security and component quality are high. The basic application areas for external turning are longitudinal turning (1), profile turning (2), and face turning (3).

With PrimeTurning™ you can do turning in all directions, with faster metal removal rates and the highest productivity.

Longitudinal turning

For longitudinal turning, the feed movement of the tool is along the axis of the workpiece, which means the diameter of the part will be turned down to a smaller size. This is the most common turning operation.

When choosing a tool for longitudinal turning it is recommended to choose the clamping system of the insert in the tool holder first. What to choose is determined by the type of operation and, to some extent, the size of the workpiece. Roughing operations on large workpieces has considerably different demands than finishing operations on small components.

Insert shape

The largest suitable insert nose angle should be selected for strength and cost efficiency.

Entering angle

The entering angle of the tool affects the chip formation. At an entering angle of 90° (lead angle of 0°), the chip thickness is the same as the feed, f_n. A smaller angle, 75–45° (15–45° lead angle), will reduce chip thickness and enable an increase in feed.

Tool holder

If there is a shoulder to machine in the component, use a tool with 91–95° entering angle (-1 to -5° lead angle). Use a C-style (80°) insert as first choice.

A D-style (55°) insert will allow profiling or undercuts.

If there is no shoulder to be machined, productivity can be increased by selecting a square insert and a 75° entering angle (15° lead angle).

Turning tools for longitudinal turning

Profile turning

In profile turning, the cut can vary with regard to cutting depth, feed and speed. Tools used for profile turning are subjected to large variations in stress and depth of cut due to the varying machining directions and diameter changes. One of the most important properties of a profiling tool is accessibility.

Insert shape

The largest suitable nose angle on the insert should be selected for strength and cost efficiency, but the insert nose angle has to be considered in relation to accessibility. The most frequently used nose angles are 35° and 55°.

Entering angle

Analyze the workpiece profile in order to select the most suitable entering angle. A free cutting angle of at least 2° between the workpiece and the insert has to be maintained. However, for reasons relating to surface finish and tool life, at least 7° entering angle (83° lead angle) is recommended.

Tool holder

First choice is a tool with 93° entering angle (-3° lead angle) and a D-style (55°) insert. If a larger ramping angle is needed, use a V-style (35°) insert.

For the possibility to profile in another direction or to make a corner relief, choose a holder with a 107–117° entering angle (-17 to -27° lead angle).Turning tools for profile turning

Face turning

In face turning, the tool is fed radially towards the centre, at the end of the workpiece. The radial cutting forces are high, which may generate deflection on the component and may sometimes also cause vibration.

Insert shape

The insert shape should be selected according to the required entering angle and in relation to the accessibility or versatility required for the workpiece. The largest suitable nose angle on the insert should be selected for strength and cost efficiency.

Entering angle

75° entering angle (15° lead angle)

A reduction of the entering angle, (increasing of the lead angle) can redirect some of the radial forces axially toward the chuck for better stability and reducing vibration tendency.

Tool holder

For optimization, choose a holder with a square insert and a 75° entering angle (15° lead angle).

For versatility, choose a holder with a rhombic 80° or trigon insert and a 95° entering angle (-5° lead angle).Turning tools for face turning

PrimeTurning™

PrimeTurning™ is a strategy where you enter the component at the chuck and remove material in the direction towards the end of the component, instead of the conventional way from end to chuck. This way of turning is much more efficient and productive compared to conventional turning.

This strategy offers the flexibility to do turning in all directions, which means longitudinal, facing and profiling operations with a single tool. Furthermore, conventional turning can be performed with the same tool – but then with conventional productivity results.

Small entering angle

PrimeTurning™ provides perfect reach at the shoulder and allows for entering angles of 25–30° (65–60° lead angle). The small entering angle will create a thin and wide chip which spreads the load and heat away from the nose radius. This results in increased tool life or allows for increased cutting data which provides considerable productivity gains.

Conventional turning vs. PrimeTurning™

Excellent chip evacuation

Chip jamming can be a common problem when using conventional longitudinal turning. With PrimeTurning™, the cutting is performed in the direction moving away from the shoulder, which means there is no risk of chip jamming.

When to use PrimeTurning™

Due to increased radial forces, this method requires stable components and a stable set-up. It is best suited for short and compact components and the slender ones using tail stock. PrimeTurning ™ is a very good choice for mass production or components needing frequent set-ups and tool changes.Read more about our CoroTurn® Prime tools

Heavy turning

A typical heavy turning application is turning of large components with uneven surfaces in combination with very large and varying cutting depth.

The time in cut is normally very long which leads to high temperatures. The cutting speed and number of revolutions is often limited to the size and clamping of the component. Machining is often performed in dry conditions as the machines are open and not suited to wet machining.

Examples of components are big shafts for Power energy, propeller shafts and shields for nuclear and big containers.

Bar peeling

Bar peeling is a method that is used to remove oxide scale, mill scale, surface cracks, etc. from hot-rolled and forged blanks. Bar peeling is also applied to thick walled tubes.

The most common materials that are peeled are carbon steel, spring steel and stainless steels.

Application areas vary, but bar-peeled blanks are often used as an intermediate stage in the production of products that are to be processed further. Examples of these are extrusion blanks for tube manufacturing and axle components for the automobile industry.

Compared with conventional turning, bar peeling is a method of machining that provides high productivity and low production costs due to the shorter throughput times. The surface quality and dimensional tolerances are also high, which in turn leads to less machining at subsequent stages.Turning tools for heavy turning

Want to know more about re-turning and new wheel turning? Read our Railway turning application guide.