Modular Tooling is Key to Turning Productivity

Turning machines went through a momentous change during the 1960s, when tool engineers started experimenting with holding the cutting tool mechanically, rather than brazing it into the toolholder. That seemingly simple change had a far-reaching impact on the machine shop. In fact, it had major implications for the metal cutting industry as a whole.

Brazing had presented some problems. For one thing, it created limitations on the cemented carbide and geometry. For another, a regrinding facility was needed for the continued use of the toolholder once the edge was worn out.

Mechanical clamping of the tip led to improvements not only in the tool material, but also to the design and manufacture of the indexable insert.

When indexable inserts were first introduced, people were quick to recognize the importance of being able to make quick tool changes just by undoing a clamp or screw. How ever, as NC machines became more common, problems arose with inaccuracies in locating the insert in the holder. Measuring cuts were usually necessary. Adjustments to multispindle automatics and programming offsets into the NC units took time, even though the change to a new cutting edge was fast. So, some way had to be found to reduce machine downtime.

The first couplings were developed during the late 1970’s. The block Tooling System for turning was introduced by Sandvik in the 1980s. The concept of coupling a cutting unit to the toolholder was soon recognized as a simple way to achieve higher efficiency.

Sandvik’s invention had to answer a number of criteria before modular tooling could be accepted:

1) higher accuracy of coupling;

2) stability comparable to solid tools;

3) weight and length about a third that of a conventional tool;

4) suitability for mechanical handling;

5) capability to accommodate all tools used on a lathe;

6) capability for internal coolant supply;

7) fail-safe toolholder with coupling accommodated within lathe parameters;

8) suitability for manual operation of the coupling mechanism.

Keeping these requirements in mind, some forty different prototypes were tried before the square shank BTS coupling was established. A square shank meant that the drawbar for force could be applied fully at the top of the shank to resist tangential bending forces from the cutting operation.

Numerically Controlled Chucking Lathe

A special numerically controlled chucking lathe, model MK 6713, is designed for producing rings, discs and flanges up to 1000 mm in diameter, and also for tapping holes for screw fasteners. The machine is used in the bearing industry to turn large diameter rings with complex-profile roller raceways, in the aircraft industry, and in the industry producing fitting for gas and oil-pipelines and atomic power stations.

The whole machining process except part loading and unloading is automated. The spindle is driven from a nine-speed thyristor-controlled d.c. motor mounted in the headstock. By changing over gear wheels the range of spindle speeds can be additionally extended from 2.5 to 520 rev/min.

The tools are held in an automatic six-position turret. Its cross travel is square with the spindle axis to within 12 m over a distance of 300 mm. The spindle unit is mounted in precision double-row antifriction bearings that ensure accurate rotation.