One of the most interesting types of production that we came across in the past period is the processing of hexagonal and square holes, which has a more popular term – broaching.
At the first sight this type of processing may look complicated, but is quite simple actually. The tool’s integral parts are the carriers and cutting bit that can have different shapes, depending of the desired shape of the technical hole.
On the photo bellow you may see an example of the finished piece:
Photo 1. Threaded plug Hexagonal 10
For this piece we used a tool set from Garant Hoffmann Group.
Hexagonal, square, triangular, torx and so on are just a few most usable forms of this tool, as there are literally an infinite number of combinations.
Photo 2 shows a set of cutting bits for hexagonal processing, with sizes from 6 to 17 mm.
Cutting bit is assembled on the carrier which allows a free rotation of the axle and lathe processing. The tool is usually tilted for 1 degree which allows the cutting process.
Photo 2. Hexagonal cutting bits
The workpiece is prepared by pre-drilling a hole of the appropriate diameter (relative to the size of the hexagonal cutting bit), and then the edge is deburred in order to make more controllable cutting process.
The workpiece is tightening in the clamping head of the lathe and rotates as the tool approaches to it. At the moment of contact between the tool and the workpiece, they start rotating together and, due to the tilt mentioned above, cuts the tool’s profile.
It is interesting that in this type of processing, the chip has no way to get out of the technical hole, as the tool pushes it in front making chip remnant in case of the hole.
Photo 3. Cutting edge of the insert after about 600 pieces
For this reason, a deeper hole is drilled in order to ensure that the hexagonal shape is of adequate depth, and the finish ends with another pass of a drill with slightly smaller diameter, which cleans the previously deposited chip and produces a technically correct piece.
It is also worth noting that this method of making hexagonal holes is fast, economical and with satisfied precision.
Materials that can be processed in this manner should be softer.
It is desirable to cool the cutting zone with cutting oil, or concentrated emulsion.