Walter AG has expanded its Tiger·tec Silver® range with three efficient, positive, steel cutting geometries – an often underestimated insert type, which shows its full potential with low cutting pressures and on small diameters.
The three new ISO P geometries with a positive basic shape are called FP4, MP4 and RP4. The indexable inserts for steel machining are available in the proven WPP10S, WPP20S and WPP30S Tiger·tec Silver® cutting grades.
FP4 (F = finishing) is optimised for finishing steel and achieves the best surface finish quality and chip control for exact precision machining. MP4 (M = medium) for mid-range steel machining is the universal design of the three new inserts and is particularly well suited to machining long-chipping materials, such as St37 structural steel or other low-carbon steels. The geometry is available with two clearance angles (7° and 11°), as well as in a precision-sintered and a precision-ground design. The clearance angle of 11° enables machining of smaller diameters. Precision grinding provides an indexing accuracy of +/- 25 micrometers, which is twice as accurate as sintering and ideal for precision finishing. RP4 (R = roughing) has a very stable cutting edge for roughing forged steel parts or casting skins. This insert is first choice for maximum machining volumes. The FP4 and MP4 geometries were optimised in particular for short chip breaking, which is very effective on long-chipping materials such as structural steels.
Problem-solving: With a positive insert, you have two to four cutting edges, a negative insert has double the number of cutting edges: therefore, your initial thought is that the positive insert is less economical. However, the positive basic shape offers a host of advantages: lower cutting pressures and a softer cutting action for machining smaller diameters or very long, unstable components. Where these attributes are needed, this positive insert makes economic sense. On multi-spindle machines, you can, for example, achieve higher feed rates thanks to the reduced cutting pressure and at the same time benefit from excellent chip control. Positive inserts are, in many cases, problem solvers; when working with very small internal diameters for example. They can be used from 8.5 mm in this respect.
Performance-enhancing: Tiger·tec Silver® in combination with the new geometries allows an increase in performance of up to 75 percent. During a field test of an MP4 insert made from WPP10S Tiger·tec Silver® at a customer in the US automotive industry, Walter AG was able to machine 60 components in comparison to the 35 achieved with a competing product. In addition, only one dimensional correction instead of the usual five was required for maintaining correct size.
Informative: Information which previously could only be found on the indexable insert packaging is now also lasered onto each individual insert – as is already the case for negative geometries. The cutting tool material, radius and geometry are lasered onto the side of each insert. This helps minimise the risk of machine operators mixing up the inserts and therefore reduces scrap components.
Sharp: Conventional aluminium oxide coating crystals are rough and easily tear out of the coated surface. In a Tiger·tec Silver® layer, the crystals are aligned, reducing tear out and as such, wear out more slowly. It is important to specifically influence crystal growth during the CVD coating process so that the coating grows parallel to the cutting surface. Finally, a mechanical post-treatment transforms the tensile stresses which result from cooling through various expansion coefficients into compressive stress. This enables the inserts to maintain their integrity for longer, especially when machining interrupted cuts.