Interpreting Tool/Feed Marks

Categories: MillMax Tips

If you milling at a stable speed and are getting vertical marks on the wall of the part that you wish to eliminate, follow the following procedure:

Measure the distance between the peaks of the lines.You can do this with a pocket comparator with the appropriate reticle. A digital caliper could also be used with the inside measurement jaws. If the part is inaccesible to measure you could create a facsimile by rubbing a pencil's lead on the marks and transferring it to a piece of paper.

If the distance equals the feed per revolution (found on the Dashboard in inch or metric), this is caused by runout. If you have increased the spindle speed significantly, the runout could be induced by imbalance of the tool assembly and the effect of centrifugal force from the increased speed.

If the distance is equal to the feed per tooth, then these are feed marks. 

You can minimize feed marks by selecting a speed with the lowest Cutter Dynamic Displacement (CDD). That is the gage in the lower right of the Dashboard and the CDD is measured low, from the bottom of the graph, to high. You may have to reduce the width and/or depth of cut to stabilize the low CDD speed.