# TOOL GEOMETRY. MACHINING WOOD A Stress Failure Process With Three Objectives. 1.Severing – To make two or more pieces from one 2.Shaping – To impart a.

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TOOL GEOMETRY

MACHINING WOOD A Stress Failure Process With Three Objectives. 1.Severing – To make two or more pieces from one 2.Shaping – To impart a shape or contour on a piece of wood 3.Surfacing – Sanding, jointing or planing an edge or surface

MACHINING WOOD The tools

MACHINING WOOD The tools

MACHINING WOOD

MACHINING WOOD IDEAL CUTTING ACTION

MACHINING WOOD HERE IS WHAT HAPPENS Wood fails when ultimate stress is reached. Stress is accompanied by strain. The work piece deforms ahead of the cut and both work piece and chip spring back.

TYPES OF CUTTING ACTION ORTHOGONAL CUTTING PERIPHERAL MILLING

TYPES OF CUTTING ACTION 1.ORTHOGONAL CUTTING The tool edge is more or less perpendicular to its direction of travel The cut is parallel to the edge or surface of the board Examples: Pushing a hand plane across the surface of a work piece Using a cabinet scraper

TYPES OF CUTTING ACTION 2.Peripheral Milling – A rotary cutter head with one or more cutting edges intermittently coming in contact with the work piece Jointer Router Planer

TYPES OF ORTHOGONAL CUTS 90° TO 0° - Planing along the grain 90° - Relationship of the cutting edge to grain 0° - Relationship of the direction of cut to the direction of grain

TYPES OF ORTHOGONAL CUTS 90° to 90° Cutting (Planing End Grain) Requirements for a good cut Low cutting angle Sharp edge High clearance angle

TYPES OF ORTHOGONAL CUTS A closer look at 90 to 90 cutting

TYPES OF ORTHOGONAL CUTS

The Effects of Skewing

TYPES OF ORTHOGONAL CUTS O° TO 90° CUTTING VENEER SLICING

TYPES OF ORTHOGONAL CUTS Type I Chip Large rake angle Small chip Grain failure occurs out in front of the knife Cutting angle ~ 45° sharpness  30° clearance  15°

TYPES OF ORTHOGONAL CUTS Type II Chip Smaller rake angle Compression rather than upward lifting Failure occurs right at the cutting edge

TYPES OF ORTHOGONAL CUTS Type III Chip 0° to small rake angle Uses compression to produce failure Snow plow effect Not an acceptable chip type

TYPES OF ORTHOGONAL CUTS CUTTING QUALITY

TYPES OF ORTHOGONAL CUTS When you can’t cut with the grain the chip breaker can help

TYPES OF ORTHOGONAL CUTS

PERIPHERAL CUTTING Revolving cutterhead operating along an edge or face of a board Creates knife marks which should number between 12 and 25 per inch

PERIPHERAL CUTTING

Jointer Planer Router Refer to pages 166, 167 & 168 for peripheral cutting problems.

MACHINING WOOD

The tools

MACHINING WOOD www.technologystudent.com/equip1/planes1.htm www.fine-tools.com/rauh.htm

MACHINING WOOD

Bench Chisels

MACHINING WOOD Paring Chisel

MACHINING WOOD Cranked Paring Chisels

MACHINING WOOD Mortising Chisel

MACHINING WOOD Mortising Chisels

MACHINING WOOD

Types of saw blades  Plywood or cross cut blade 60 to 80 teeth large top bevel small gullets  Rip blade 20 to 60 teeth no top bevel larger gullets

MACHINING WOOD  Combination blade 40 teeth Square tooth followed by beveled teeth Large gullets  Laminate blade or “triple chip” blade 80 teeth typical Small gullets