Maintaining T-12 Dimension
On Blades Used In Rake Angle Tools

The full efficiency of Genesee Adjustable Hollow Mills with 12 degree rake angle depends upon the shear action of the blades. The throat length of the blades must be ground so that when the mill is adjusted to the finish diameter the blades are the correct distance ahead of center. The smoothness of the finish depends upon the efficiency of this shearing action. The blade grinding instructions contained in our catalog and our T-12 formula are designed to show correct angles and throat lengths for ordinary work.

Maintaining the proper T-12 dimension on rake angle blades requires that adjustment of the Hollow Mill to size occur through the maintenance of the T-12 dimension, NOT through adjustment of the blades with the ring. Adjustment with the ring should only be necessary to make the small adjustments necessary to set the Hollow Mill to size after regrinding.

If the T-12 dimension is too short, the blades will be too far behind centerline at the cutting diameter, thereby producing chatter and/or rough finish.

If the T-12 dimension is ground too long, then the blades will be too far ahead of centerline at the cutting diameter and produce a tapered part larger at the end of the cut and/or poor finish.

WHEN ORDERING Rake Angle Hollow Mill blades please be sure to tell us what diameter you will be hollow milling and we will insure that your blades arrive with the proper T-12 length ground for your job.