This is a little trick I picked up a few years ago. I dont know of anyone who has written down a procedure for dialing milling tools. I have seen many methods of obtaining low runout on tooling held by collets. From randomly changing holders, collets, collet nuts and tools to tapping tool shanks with hammers! This by far is the best and most accurate method and if you always follow the same logical order, it can be done very quickly.

Enjoy,Machining Nerd

DIALING A COLLET STYLE TOOL HOLDER.

1. Both your spindle and tool holder taper should be cleaned with alcohol and a lint free cloth then oiled with a light hydraulic oil. When using HSK or other dual contact tools also clean the flange on the holder.

2. Usually on holders with any amount of extension there is a ground section on the outside of the holder. Using a .0001 resolution or finer indicator dial this section.

Unless you are using hsk tooling, you can then turn the tool holder 180 degrees in the spindle and dial again. Sometimes this 180 degree change can make a difference in the run-out of the holder.

Another reliable way to test the holder is to dial the actual surface the collet seats against. This can be done using a dial test indicator. Always ensure your test indicator is set at the manufacturer recommended angle in relation to the surface you are gauging.

Once you have checked the tool holder you can determine if the quality of the holder is acceptable for your task.

3. Use a quality collet. Many manufacturers recommend not mixing different brands of holders and collets. Inspect a collett for damage on its tapers and central bore. Clean any chips or grime with alcohol and a small brush and dry with compressed air or lint free rag.

4. Complete the tool assembly by ensuring all of the components are clean and free of contaminates. Lightly oil or molybdenum grease the collet seat and wipe away again. This leaves a thin lubricating layer to aid disasembly. Also lubricate the threads of the holder where the collet nut goes. You should then snap the collet into a clean nut and screw onto the holder.

To aid the dailing procedure align the splits in the collet with the drive dogs or other referance on the holder. Place the tool in the collet at the desired extension and align the flutes of the tool with the same referance as the collet.

5. Place the holder in the machine. If the tool shank is accesable dail the shank of the tool just outside the collet.  Note the runout. You can then dail the flutes of the tool, again close to the end of the flutes. Any deviation between these two runout values could indicate that the flutes ate not ground concentric to the shank of the tool.

To correct runout the goal is to arrange coaxality errors in the assembly to achieve minimum or acceptable levels of runout. The furthest diameter of the tool from the nose of the toolholder is where error will be most apparent.

After noting the runout of the tool. Remove the tool from the machine. After each of the following steps re-tighten the assembly and test the runout.

A. Turn the collet 90 degrees.

If runout is reduced: turn collet in 45° increments in same direction as first turn. Keep track of your collet position between each dailing and find the zone that gives the best result.

If runout increases: Turn the collet in the opposite direction 180 degrees and check again, then again zone in on the collet position that gives you the lowest runout value.

B. Turn the tool. Note the position of the tool. Since you have already found the “sweetspot” of the collet try not to disrupt it’s alignment in the nut and holder. Turn. The tool first 90 degrees and then smaller increments until you find its lowest runout.

Repeat until acceptable runout is obtained.