Smithy Midas 1220 XL - Manual (Page 95)

Tool Grinding
Sharpen cutting tools when they become dull, or extreme forces may build up at the
cutting edge of the teeth, causing chipping or fracture. Dull cutters are also inefficient,
and regrinding very dull cutters shortens their life considerably.
The form of the cutting edge and the clearance back of the cutting edge (land) affect
cutter operation significantly. The angle formed by the land and a line tangent to the
cutter at the tooth tip is the primary clearance. The angle between the back of the land
and the heel of the tooth is the secondary clearance. Check both clearances and the rake.
Some cutters are sharpened on the periphery by grinding the land at a suitable angle.
They include cutters with straight or spiral teeth, angular cutters, side milling cutters, face
mills, end mills, and reamers.
You sharpen others by grinding the front faces of their teeth. Formed or relieved cutters,
for example, have profiles that must be preserved. This category includes all sorts of
formed cutters as well as cutters used for milling various regular and irregular shapes.
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Milling Cutters