Video: Retention Knob Tightening And Toolholder Deflection
This footage illustrates how the toolholder taper is measured in a test designed to capture the retention knob’s effect on the shape of the toolholder taper.
In a tapered toolholder, tightening the retention knob can produce deformation of the toolholder that can prevent the holder from seating properly in the spindle. J&M Machine offers a “high-torque” retention knob design that attempts to address this problem. This knob has threads that grip deeper into the holder, where the holder has more mass to resist deformation. This video, which the company produced, shows the toolholder deformation being measured for the high-torque and standard knob designs. The article under “Editor Picks” at right provides more detail.
To make the transition to hard turning, you'll need to switch from carbide to CBN inserts, but that is easier (and more economical) than you might think. It's making the jump to much higher surface speeds that might scare you off. It needn't. Here's why.
With macros and canned cycles resident in the CNC on most contemporary turning centers, single point turning of OD threads can seem like almost a default process decision. However, for numerous applications, OD thread rolling has inherent advantages as an alternative to cutting threads.
Running rotary milling cutters at the proper speeds and feeds is critical to obtaining long tool life and superior results, and a good place to start is with the manufacturer's recommendations. These formulas and tips provide useful guidelines.