Excellent surface finishes can be achieved with standard inserts in combination with one or more wiper inserts. Wiper inserts work most usefully at a high feed per revolution, fn, in larger diameter cutters with extra close pitch and setting facilities.
Feed per revolution can be increased approx. four times while still maintaining good surface quality. Wiper inserts can be used in milling in most materials to produce good surface textures – even under unfavorable conditions.
A wide range of wiper inserts is available for finishing of most materials. Larger diameter cutters with cassette design have facilities for axial setting.
A wiper insert is available that has two right-hand and two left-hand wiper edges.
Two wiper inserts are available
- One with two right and two left-hand edges
- One with an extra long wiper and with one right and one left-hand edge.
Larger diameter Cap cutter versions are axially adjustable by using shims.
A system for highly accurate setting allows the use of wipers in more than one insert seat in larger cutters, and in all insert seats in smaller cutters, which provides for extreme productivity while maintaining the high surface finish. The insert grades available cover wiper finishing of most materials.
All cutter sizes have adjustable cassettes with insert seats suitable for either L-type or F-type wipers, with a longer wiper edge. Larger diameter cutters are of Cap design.
Larger diameter cutters are of Cap design and axially adjustable by using shims. A wiper insert with four edges is available.
- When fn exceeds 80% of the length of the parallel land, bs, on standard inserts, a wiper edge will improve the surface.
- When feed per revolution, fn, increases in large cutter diameters with a higher number of inserts, the need for wiper inserts becomes essential for maintaining surface finishes.
- The cutter's axial run-out, which depends on spindle inclination, cutter size, mounting and the accuracy of its setting, influences the waviness of the machined surface. The crowned wiper land will compensate for this and produce a step-free surface. A feed per revolution limited to 60% of the wiper land will ensure this.
- A wiper land protrudes below the milling inserts by approximately .0020 inch (0.05 mm), when mounted in cutters with fixed insert seats. For CoroMill cutters of cassette design, the wiper edge can be adjusted to this position with great accuracy. The protrusion subjects wiper inserts to greater loads than conventional inserts, which can lead to vibration. Therefore, wipers should be used for light machining at moderate cutting depths and in limited numbers.
- Depth of cut should be light to limit the axial forces and to reduce the risk of vibration. In finishing, the recommended axial depth of cut is .031 – .039 inch (0.8 – 1.0 mm).
- Extra care is required when mounting a wiper insert to correctly position its long edge.
- The width of the parallel land, bs, on the insert is .059 inch (1.5 mm).
- There are 10 inserts in the cutter, and the feed per tooth, fz, is .012 inch (0.3 mm). Feed per revolution, fn, will be .118 inch (3 mm), i.e. twice the length of the parallel land.
- To ensure a good surface finish, feed per revolution should be a maximum of 80% of .059 inch (1.5 mm) = .047 inch (1.2 mm).
- A corresponding wiper insert will have a parallel land with a width of approx. .315 inch (8 mm).
- Result: Feed per revolution could be increased from .047 inch (1.2 mm) to 60% of .315 inch (8 mm) = .189 inch (4.8 mm).
Note: Other limitations, such as machine power, must be taken into consideration.
Additional hints to achieve a “mirror finish”
- Use high cutting speed and/or Cermet inserts to obtain a shiny surface.
- Use cutting fluid or oil mist for sticky ISO M and S materials.
- PVD-coated inserts with sharp edges and an ap of .020 – .031 inch (0.5 – 0.8 mm) produce the best surface finish.