Can Tap-Testing be used with resharpened endmills?
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Yes, tap-testing can dramatically improve an endmill resharpening/reconditioning program.
Typically, resharpened endmills are run at much slower speeds than new. When you tap-test you can find optimized and stable speeds that will work for new and resharpened endmills.
Here is a stability lobe diagram with five overlays. The new endmill is in red. Regrind #1 in light blue (0.005” removed from diameter and length), Regrind #2 in purple (0.010”), Regrind #3 in green (0.015”) and Regrind #4 in burgundy (0.020” removed). As you can see the lobes shift faster in RPM and slightly deeper in the axial depth of cut (because the tool is become shorter and stiffer with each regrind). The yellow area of the lobe is stable
Tap-test a new endmill in the toolholder in the spindle of the target machine. Generate the Dashboard.
Next, tap-test a resharpened endmill after its last possible regrind in the same holder and machine. Generate it's Dashboard.
Compare the two Dashboards and find a speed and depths of cut that are stable for both endmills. Use those parameters and now you can co-mingle new and reconditioned endmills, using them with no loss in performance, IF the following are maintained.
- Use the new and resharpened endmills with Dashboards in the same toolholder in the same machine.
- Control the endmill stick-out.
- Your machine should have tool probing so it can automatically compensate for the reground endmill's new dimensions.
- Your tools should be re-manufactured to the same geometry as new. Just grinding down the primaries until sharp changes the tool's rake angle and will impact performance.
