Next generation synchronised tap holder designed to turbocharge tapping performance.

Modern CNC machine tapping centers are designed to synchronise spindle rotation with the feed axis. In rigid tapping high axial forces have to be absorbed by the tap’s thread flanks. This increased abrasive flank wear reduces the tool life of the tap as well as the surface quality and accuracy to gauge of the thread resulting in a significant decrease of process reliability. This may result in breakage of the tap. SynchroFit Tap Holder with its new wear free radial cutting force compensation reduces the tap flank wear significantly.

Machining troubles associated with tap processing are far more frequent in comparison to other rotating tools, such as drills and end mills. Manufacturers often struggle with threading applications because there are few effective solutions. For example, what kind of measurements would you take to achieve the following: Prevent sudden breakage of taps; stabilise tap life; improve thread quality; stabilise short chamfer taps’ performance.

All of the above are difficult to achieve. When a tapping problem arises, most operators would troubleshoot by lowering the cutting speed, which would in turn reduce productivity.

To help manufacturers who use machining centers with synchronous spindles overcome these common tapping obstacles, OSG Corporation has recently introduced a new generation synchronised tap holder – the SynchroMaster – engineered to turbocharge performance by dampening excessive forces in rigid tapping environment.

Why tap processing is difficult
One of the causes is that the feed per revolution is fixed. The cutting of internal threads is performed by the chamfer section of a cut tap. In principle, the full thread portion of a cut tap does not perform any cutting, but merely follows the path cut by the chamfer. As the tap rotates, each cutting edge of the chamfer gradually increases the depth of cut along the lead, which forms the thread ridges to guide the position of the tap thereafter.

Rigid tapping, also known as synchronous feed tapping, is one of the most common tapping methods used on modern machining centers. If the machine’s spindle rotation and feed are synchronised to match a specific thread pitch as the tap is driven in and out of a hole, the shape of the pitch would be correctly formed. When there is a feeding error (leading or delaying), a size reduction (pitch dislocation or enlargement) would occur, which affects the precision of threads.

With the right combination of machining center and tap holder, feeding error can be prevented
Theoretically, a solid type tap holder without any tension-compression is appropriate for machining centers with synchronous spindles. However, there will always be small discrepancies between the synchronisation and the actual movement (feed) of the specific tap being used. As the machine ages, the discrepancy between the spindle speed and feed and the tap’s movement can become more significant. With a solid holder where no movable value is permitted, any deviation occurred would increase the thrust load on the tap, which would greatly reduce tool life and thread quality due to the extra axial forces being exacted.

Features and benefits of SynchroMaster
The SynchroMaster is a tap holder constructed to allow a slight amount of axial movement to compensate for axial deviations that are unavoidable in rigid tapping. Its micro tension-compression float eliminates the extra axial forces on the tap, leading to longer tool life, consistent tapping depth and improved thread quality.

Cutting data
OSG carried out a tool life test comparison of a short chamfer tap when used in combination with the SynchroMaster tap holder and a solid type holder. The cutting tool used for the test was a M4 x 0.7 1P short chamfer spiral tap. The shorter the chamfer, the cut made per cutting edge increases. For this reason, applications with short chamfer taps can easily become unstable. Tapping in S45C, the M4 x 0.7 1P short chamfer spiral tap with solid type holder averaged approximately 200 holes. When use in combination with the SynchroMaster tap holder, on the other hand, thrust load was significantly reduced and the short chamfer tap was able to achieve nearly five times the durability versus the solid type holder.

The SynchroMaster tap holder is effective not only for cut taps, but also for form taps. Since cutting does not take place with form taps and the internal thread is processed by using the plastic deformation of the material, the processing load for form taps is even higher than cut taps. The SynchroMaster tap holder is able to double the tool life versus solid type holder even for form taps.

For manufacturers who are especially struggling with unstable tool life, poor thread quality, low productivity and large variations in depth length on rigid tapped holes, look to the SynchroMaster tap holder to turbocharge your tapping performance.

For further details contact Somta Tools on TEL: 011 390 8700 or visit www.somta.co.za