© 2008 Metal Arts Press Extracted from Machine Shop Essentials: Q & A

Lathe Tool Sharpening What are typical rake and clearance (relief) angles for HSS tool bits? See Figure A–1 and Table A–1.

Face

CuttingEdge

NoseNoseAngle

Side Cutting Edge Angle

Body

Front Cutting

Back Rake Angle

Side Rake

Side Clearance

Edge Angle

Angle

End Clearance AngleAngle

Figure A–1. Tool bit nomenclature.

Material Side Clearance

Front Clearance

Side Rake

Back Rake

Aluminum 12 8 16 35

Brass 10 8 5 to −4 0

Bronze 10 8 5 to −4 0

Cast Iron 10 8 12 5

Copper 12 10 20 16

Machine Steel 10–12 8 12–18 8–15

Tool Steel (unhardened) 10 8 12 8

Stainless Steel 10 8 15–20 8

Table A–1. Clearance and rake angles in degrees for common metals.

© 2008 Metal Arts Press Extracted from Machine Shop Essentials: Q & A

What is the procedure for sharpening HSS general-purpose lathe tools? Begin by dressing the grinding wheel. Next, look up the typical angles for the workpiece material, and then follow the steps in Figure A–2. Dip the tool in coolant frequently to keep it from overheating and annealing. Any discoloration on the bit indicates it may no longer be hardened. If this happens, consider starting over again from the beginning. Tool bit angles are not critical and most tools will cut material satisfactorily, just less effectively.

Top

Top

Top of Tool8°

Set Tool Rest Angle1 Move Tool Side to 2Side Across Wheel

Side Cutting3Edge Complete

Move Tool Side to 4Side Across Wheel

Front Cutting5

Break Point to61/64" Radius

Apply Back Rake7

Cutter Complete8

Do Not Remove This EdgeWhen Grinding Rake

on Grinding Wheel

Grinding Wheel Tool Rest

Edge Complete

Figure A–2. Steps for sharpening HSS tool bits