Internal broaching

This video shows two internal broaching processes with static and live toolholders. Making the keyways with broaching toolholders on a CNC lathe reduces time since the part is made in a single operation, compared to the usual process of outsourcing broaching. This translates into a significant reduction in cycle times.

It is quite common to find features like internal and external keyways in our drawings. Sometimes these are machined in a separate operation in a standalone broaching machine or they are simply subcontracted. Anyhow, in some cases, there is tooling that allows you to perform these operations in a CNC lathe.

Broaching operations can be performed in different ways depending on the type of tool and holder used:

HOW TO MAKE INTERNAL KEYWAYS WITH A FIXED TOOLHOLDER IN A CNC LATHE

The easiest way to broach on a lathe is to use a fixed toolholder as no live tooling or Y axis is required.

For this type of process, the broaching tool is mounted on a standard internal tool holder and a bushing. Several shallow passes have to be done until the required dimension is achieved.

Tips are included in the downloadable that we have prepared to ease the programming of internal figures with the special macro of CMZ M385.

For the part shown, the cutting conditions are as follows:

• Material: steel
• Width: 5 mm.
• Length: 45 mm.
• ap = 0.1 mm
• f = 5000 mm / min

HOW TO MAKE INTERNAL KEYWAYS WITH A LIVE TOOLHOLDER IN A CNC LATHE

An alternative to make internal keyways faster is the use of live slotting toolholders. The operation we show is an example of internal broaching programming with a live tool. It has been filmed directly by MT Marchetti, a leading European tool holder manufacturer, and owner of the TTL-52-52-T1Y-T2Y manufactured and delivered by CMZ in 2019. This multi-turret lathe is usually employed by MT Marchetti to test and demonstrate the quality of its products.

This type of toolholder converts the rotational movement of the live tool into one of translation. For this reason, it is only necessary to program the movement in the X axis. The downloadable includes a specific programming example for internal broaching with a live tool.

Do you need help to carry out internal broaching on your CNC lathe? Our applications department can analyse in detail the process offering you a part study helping you to significantly reduce cycle times.