1. Grinding Lathe Cutting Tools
Unit 50

2. Objectives
Explain importance of various rakes and clearance cutting-tool angles
Grind general-purpose cutting tool from blank
Resharpen dull cutting tool

3. Grinding Lathe Cutting Tool
Wide variety of cutting tools for lathe
All have certain angles and clearances regardless of shape
Shape and Dimensions of General-purpose Lathe Toolbit
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4. To Grind a General-Purpose Toolbit
Dress face of grinding wheel
Grip toolbit firmly, supporting hands on grinder toolrest
Hold toolbit at proper angel to grind cutting edge angle
Tilt bottom of toolbit toward wheel and grind 10º side relief or clearance angle
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5. Cutting edge ~ ½ In long and extend over ¼ width of toolbit
10º side relief or clearance angle
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6. While grinding, move toolbit back and forth across face of wheel
Prevents grooving wheel
Toolbit must be cooled frequently during grinding
Never overheat toolbit!
Never quench stellite or cemented-carbide tools
Never grind carbides with aluminum oxide wheel

7. Grind end cutting edge so it forms angle of a little less than 90º with side cutting edge
Hold tool so that end cutting edge angle and end relief angle of 15º ground at same time
70º to 80º Point Angle
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8. Using toolbit grinding gage, check amount of end relief when toolbit is in toolholder
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9. Side rake ground the length of the cutting edge
Hold top of toolbit approximately 45º to axis of wheel and grind side rake to approximately 14º
Do not grind below top of toolbit
Creates a chip trap
Side rake ground the length of the cutting edge
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10. With oilstone, hone cutting edge of toolbit slightly
Grind slight radius on point of cutting tool, being sure to maintain same front and side clearance angle
With oilstone, hone cutting edge of toolbit slightly
Lengthen life of toolbit
Enable it to produce better surface finish on workpiece