A Fix for Rigid Tapping Errors

Although it is a well-known fact that no one or nothing is perfect, there is comfort in knowing that there are ways to compensate for some imperfection, especially when dealing with machine tools.

Most CNC machine tools now offer rigid tapping capability as a standard feature. A rigid tapping cycle synchronizes the machine spindle rotation and feed to match a specific thread pitch as the tap is quickly driven in and out of a hole. Since the feed into the hole is synchronized, in theory, a solid holder without any tension-compression can be used.

Some amount of error must be expected, though, as the machine cannot exactly match the pitch of the specific tap being used. However, this is not such an issue in new machines, but as a machine gets older, the discrepancy between the tap’s pitch and the spindle peed and feed can become more pronounced. The resulting higher thrust loads on the tap greatly shorten its effective life.

Tapping holders that allow a slight amount of axial movement to compensate for synchronous errors are available. When used, tap life and thread quality can be dramatically improved. Big Kaiser’s Mega Synchro tapping holders are described in the article “Reducing Thrust Loads During Rigid Tapping.” Tapmatic’s SynchroFlex technology is described in “Rigid Tapping—Sometimes You Need a Little Float.”

Please e-mail me if you have any suggestions for what you would like to see me write about next month.