Cross tapping with a thread milling cutter

Tip and Trick – 2011-09-05

TB-DECO

Production problems encountered by conventional tapping - such as the use of materials which are very difficult to machine, tapping blind holes with special machining requirements, i.e. flat-bottom holes, or untimely breakage - can now be easily overcome by the thread milling cutting method by interpolating axes Y2 and Z1.

Besides coping with the above, this method also results in a far longer tool life and, in spite of a succession of operations, production times are quicker than with conventional tapping.

The condition required for successful tapping is a lathe capable of interpolating axes X, Y and Z. The TB-DECO fitted to the DECO 2000 is able to interpolate all axes simultaneously and in a way which the user can parameterize fully. Consequently, an operation like the one described below, can be carried out with very simple programming!

Cross M3 tapping executed as follows:

In order to machine the above part, a thread milling cutter with a 2.1 mm diameter and pitch of 0.5 mm is used.

Description of the movement seen from above:

Milling takes place in 5 stages:

Figure 1:	STARTING POSITION OF THE MILLING CUTTER AT THE CENTRE OF THE HOLE
Figure 2:	APPROACH TO 3mm EXTERNAL THREADCUTTING DIA
Figure 3:	MILLING 1/2 CIRCUMFERENCE OF AXES Z1/Y2 AND MOVING X2 BY 1/2 THREAD
Figure 4:	MILLING 1/2 CIRCUMFERENCE OF AXES Z1/Y2 AND MOVING X2 BY 1/2 THREAD, RETURN TO POINT OF APPROACH
Figure 5:	REMOVAL OF MATERIAL FROM MILLING CUTTER, END OF MILLING

Technical data:

Milling speed: 3200 rpm
Machined material: 9SMnPb28 steel