Spindle

The boring machine is the umbrella term for a whole range of tools with which existing bores or holes can be enlarged, i.e. drilled open . Existing bores can also be brought to a specific final dimension with a very high degree of precision, e.g. B. for the production of fits in which the use of reamers is not worthwhile due to the size of the fit or the quantity of workpiece to be produced.

A distinction is made between fine boring heads, double-edged boring machines for roughing and finishing, bridge tools and modular systems with up to three cutting edges.

The main advantage of these tools is that the tool does not follow the existing hole, but with the machine axis to be fed (usually the Z axis on CNC machines). In the case of cast parts , it is thus possible to move bores that are not always 100% in their position due to the casting process or to move slightly inclined bores back to their predetermined position due to casting distortion if there is enough material on the raw part side. Another advantage is that with a relatively small selection of tools, a very large spectrum can be covered in which holes and fits can be manufactured. Due to the modular structure, holes and fits in the area up to a length of 10xD can be easily produced. The use of standard indexable inserts also provides a high degree of flexibility with regard to influencing factors such as cutting edge radius and cutting edge geometry .

Fine boring head

Fine boring heads are compact tools that are mostly equipped with indexable inserts or hard metal form turning tools and have a relatively small adjustment range of a few millimeters. These tools are designed for diameters up to approx. 40 mm and are offered in overlapping increments. Their area of application ranges from about 3 mm to about 40 mm. Using a clamp and a fine- thread spindle with scale, these tools can be set very precisely to the final bore diameter to be produced in the scale ranges of 1/10 mm, 1/100 mm or even 5/1000 mm. The most modern systems already have a digital display on the tool.

various fine boring heads

Double-edged spindles

This group of spindlers is characterized by the fact that they can be adapted to their purpose. In addition to the larger adjustment range of up to approx. 100 mm, these can be used for both finishing and roughing through deliberate modifications to the individual cutter carriers. Both cutting edges can be individually adjusted to the required diameter, and in some cases even adjusted together.

For roughing operations with a large allowance, one cutting edge is set higher and to a smaller diameter, while the second cutting edge, which is lower, is set to the final diameter of the hole. This means that the chips are split. At the same time, it is possible to use indexable inserts with different cutting edge geometries. This is done when machining cast parts that were manufactured using sand mold casting. For this purpose, an indexable insert with the largest possible cutting edge radius (for greater cutting edge stability) and an extremely tough u. Impact-resistant cutting material selected. This ensures that the inner cutting edge can remove the cast crust and thus also possible molding sand inclusions with relatively little wear, and thus creates optimal cutting conditions for the outer, dimensioned cutting edge. In roughing operation with a small allowance, both cutting edges are set the same. It is thus possible to work with double the work feedrate. The bore allowance should not be more than 1/3 of the length of the cutting edge provided by the indexable insert.

For use as a finishing tool, both cutting edges are set in the same way, however, due to the demands on the surface, indexable inserts with a smaller cutting edge radius are used.

2 cutting edge spindles of different sizes and designs

Bridge tools

This form is designed for the production of bores over 100 mm. With these tools, a bridge is attached to the tool shank, onto which the cutter holders are then screwed. These cutter holders are usually screwed onto the bridge via a locking toothing and roughly preset (usually in the 5 mm range). The fine adjustment is then carried out in the same way as the fine boring heads.

These bridge tools can be used with two cutter carrier units, as well as the double-edged boring machine for roughing or finishing, and can also be used with just one cutter carrier unit for precision drilling or fitting production. To do this, however, it is necessary to attach an appropriate counterweight on the side without the cutting edge.