There is little doubt that cutting-tool innovation can yield significant gains in automotive applications such as automatic transmissions.

Here, the switching unit is the central component that controls the clutch and transmission brake in order to change gear, according to the engine load and vehicle speed.

In the machining of the switchgear housing, the valve bores are critical, which is why Rugby-based Mapal Ltd (www.mapal.com) has developed multi-bladed PCD tools with permanently brazed cutting edges to help improve the productivity and cost-effectiveness of this operation.

The housings are machined predominantly from die-cast aluminium alloy (AlSi9Cu3Mg), with the stepped valve bores typically requiring tolerances of <8μm cylindricity, <4μm roundness and <3μm surface finish (Rz). As a result, the machining process is divided into several sequences, with different tools used for piloting, semi-finishing and finishing.

Since not every valve bore requires maximum precision, alongside finely adjustable boring tools, Mapal now offers permanently brazed PCD fine-boring tools that allow manufacturers to achieve a reduction in process time, despite a tolerance range that is only minimally extended.

In addition, the fixed multiple-bladed tools eliminate the need for any fine adjustment of the cutting edges.

For intermediate machining, a four-edged PCD tool with brazed cutting edges has been developed, which can be used as an alternative to a twin-edged standard tool as long as the length/diameter ratio, as well as the stock situation, allows.

Regarding the high standards placed on finishing work, Mapal says that although these can be met using single-bladed, finely adjustable PCD boring tools, the company now offers (depending on the application) three- to six-edge fixed PCD fine-boring tools that can provide cycle time improvements with almost the same level of precision.