ShrinkFIT v.s. ER Collet Chucks

er collet chuck and shrink fit tool holder comparison

ER collet chuck and Shrink Fit tool holder.

Comparison of cutting tool life, cutting ability, and surface finish

Techniks performed internal tool trials to assure compliance with its standard for high quality tool holders and to create a benchmark of comparison between tool holding technolgies. These tests evaluated ER collet chuck versus shrink fit technology tool holders under "real world" conditions.

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.


Test Results: Cutting Tool Life

view of cutting tools used in case study
close up view of wear on cutting tool flute held in a collet chuck tool holder
close up view of wear on cutting tool flute held in a shrink fit tool holder

The most significant comparison between these tool holding technologies is in the area of tool life. The end mill in the shrink-fit toolholder showed dramatically less wear (photos) compared to the end mill used in the collet chuck (note the fractured surface).

Our results back up other reports that shrink-fit allows 4 to 7 times the tool life of other tool holding technologies. In our tests there was significant fretting on the flange of the ER collet chuck tool holder while there was virtually no fretting on the shrink-fit holder (visible in photo above). This was attributed to the superior wear characteristics of H-13 tool steel over 8620.

photo showing fretting on taper of ER collet chuck

Test Results: Cutting Ability & Surface Finish

Cutting Ability
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.

Surface Finish
The improved concentricity and increased rigidity of the shrink fit tool holder produced a moderate improvement in surface finish of the test piece compared to the test piece machined with the ER collet chuck.


While both technologies have their place, machining using shrink-fit is a significant improvement over ER collet chuck technology. Shrink-fit has advantages in tool life, cutting ability, surface finish, and produces less wear-and tear on the toolholder shank and spindle bearings. Concerns regarding shrink-fit tool changes have been resolved by the new generation of induction heat tool changers that provide extremely fast tool changes and are safe to operate.

photo illustrating the surface finish improvement shrink fit provides

The advantages to a production machining operation using shrink-fit are outlined below.

FASTER Spindle speeds and feeds are increased to reduce cycle times. Shorter cycle times result in increased manufacturing capacity improving your R.O.I.

BETTER Concentricity of .0002” permits better balanced chip loads so machining is more accurate. This improved part finish and quality increases customer satisfaction with your product.

CHEAPER Tool life is extended by as much as 700% dramatically impacting your tooling budget. Additionally, fewer tool changes results in labor savings and reduced machine down-time. The natural balance of the shrink fit tool holder and even chip loads decreases the wear and tear on spindle bearings. Longer spindle bearing
life reduces maintenance costs and keeps machines productive longer.