This trial was performed on a CNC Vertical Machining Center with a CT40 taper. Identical tool paths, spindle speeds, feed rates, material conditions, holding devices, coolant delivery, end mills and chip loads were utilized to isolate the performance of these tool holding technologies. The test cuts were in 4140 Prehard (30-32 Rc) using 3 flute uncoated carbide center cutting end mills. The identical tool paths involved a variety of cutting directions.
Tool Life The most significant comparison between these tool holding technologies is in the area of tool life. The endmill in the ShrinkFIT toolholder showed dramatically less wear (photos) compared to the endmill used in the collet chuck (note the fractured surface). Our results back up other reports that ShrinkFIT allows 4 to 7 times the tool life of other tool holding technologies. In our tests there was significant fretting on the taper of the ER collet chuck while there was virtually no fretting on the ShrinkFIT holder (visible in photo above). This was attributed to the superior wear characteristics of H-13 tool steel ovER8620.
During our four machining test passes of .125” depth of cut, the shrink fit tool holder required less spindle load than the ER collet chuck tool holder. The increased rigidity of shrink-fit created a more balanced chip load during cutting. This was observed in a better machining sound.
While both technologies have their place, machining using ShrinkFIT is a significant improvement over ER collet chuck technology. ShrinkFIT has advantages in tool life, cutting ability, surface finish, and produces less wear-and tear on the toolholder taper and spindle bearings.