Rx for MACHINING WOOD. Gene Wengert & Bobby Ammerman

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1 Rx for MACHINING WOOD Gene Wengert & Bobby Ammerman

2 PROGRAM TOPICS 1. The Wood Part of Machining 2. Knife geometry 3. Effects of Feed Rates 4. Planer Machine Design Features 5. Sawtooth Angles 6. Sanding and Sandpaper 7. Machining Defects 8. Special Concerns

3 THE WOOD PART OF MACHINING

4 Wood machining is actually breaking of the wood. So wood strength is a key.

5 ALL ABOUT WOOD SOFTWOODS

6 SOFTWOODS Earlywood Center of tree End grain Latewood Vertical in tree Radial or quartersawn face Flat or tangential grain Spruce

7 ANALOGY: a handful of miniature soda straws Consider this analogy for * moisture movementy * gluing *machining * finishing

8 CELLS Facts * Cells are very small- -1/8 long * The heavier the wood, the smaller the cell opening and thicker the wall.

9 SOFTWOODS Earlywood Center of tree End grain Latewood Vertical in tree Radial or quartersawn face Flat or tangential grain Spruce

10 Wood machining is actually breaking of the wood. So wood strength is a key.

11 Consider - - Depth of cut Feed speed Knife sharpness

12 SOFTWOODS Earlywood Center of tree End grain Latewood Vertical in tree Radial or quartersawn face Flat or tangential grain Spruce

13 SPECIAL WOOD Compression Wood Tension Wood Juvenile Wood

14 COMPRESSION WOOD

15 TENSION WOOD Tension wood is weak and shrinks lengthwise

17 TENSION WOOD Tension wood blotchy staining

18 SAP & HEART JUVENILE WOOD-- 15 rings about Sapwood is open. Heartwood (used to be sapwood) is often closed. Juvenile wood is weak, shrinks lengthwise

19 Mature wood Juvenile

20 STRESS

21 Growth Stress RESOURCE ISSUES

22 Drying Stress (also called casehardening) causes IMMEDIATE - - Cupping when machining - - Side-bend when ripping

23 BACTERIAL INFECTION

24 BACTERIAL INFECTION * In living tree, but does not kill the tree * Anaerobic (no air) * Enters through roots * Moves 1 to 1-1/2 per year * Wet soils; older trees; bottom of butt log

25 BACTERIAL INFECTION * Secrete enzyme that destroys and weakens wood (causes shake, surface checking, honeycomb) * Creates fatty acids that turn rancid

26 BACTERIAL INFECTION What this means is * Shake (or wind shake) * Smelly wood * Very high initial MCs; longer drying time * Wet pockets in dry wood; delayed shrinkage * Checks, honeycomb and splits much more likely when drying * Planer splitting

27 Bacteria

28 BRASH WOOD

29 BRASH WOOD Slow growth causes weak, brash wood

30 MOISTURE CONTENT Lower MC means stronger wood

31 If over-dried, the wood can become brittle. Avoid under 10% MC for softwoods. Avoid under 6% for hardwoods.

32 MOISTURE

33 Hotter drying temperatures (over 160 F) worsen machining quality.

35 ANGLES to eye CIRCULAR SAW

36 Poor Side Dressing MACHINING

37 MACHINING Saw Tooth Design Flat-Top Grind (FTG)--miniature chisels; ripping Alternate-Top Bevel (ATB)--ripping or crosscutting

38 MACHINING ATB & Raker (ATB & R)-- Triple-Chip (TC or TCG)--particleboard

39 MACHINING HOOK More hook means more aggressive; pulling into the wood - ripping: 15 to 20 degrees - crosscutting: degrees - radial arm: 0 to -5

40 MACHINING HOOK - crosscutting: degrees - ripping: 15 to 20 degrees

41 MACHINING HOOK - radial arm: 0 to -8 degrees - compound miter: 0 to -5 degrees

42 MACHINING HOOK - SkilSaw: +10 degrees

43 MACHINING BEST CIRCULAR SAW Crosscutting solid wood and cutting plywood 10 diameter ATB with 40 to 80 teeth 12 diameter ATB with 50 to 90 teeth Ripping solid wood 10 ATB with 40 teeth; 12 with 50 teeth 10 FTG with 20 to 30 teeth; 12 with 30 to 40 teeth Cutting Composite Materials 10 TC with 80 teeth 12 TC with 90 or more teeth You get what you pay for

44 MACHINING DEFINITIONS

45 MACHINING BAND SAWS * Blade width --narrow turns corners (3/4 can cut nine inch diameter and 3/16 can cut about a dime size) --narrow best for resawing (narrow blade moves backward and not sideways) * Blade thickness (gauge) --thicker means more tension and straighter cuts --thicker means larger band wheels; check saw mfr. specs. --thicker means more sawdust * Set * Cleaning

46 * Cleaning MACHINING BAND SAW FACTORS * Blade width * Blade thickness * Tooth design * TPI * Tooth shape and angles * Set

49 SPECIAL CONCERNS End grain Casehardening & Growth Stress Weakened Wood Delayed Warp Delayed Checking

50 QUESTIONS

Course Syllabus ARCHITECTURE 544 WOOD FRAMING. Organization. Evaluation. Text

Course Syllabus ARCHITECTURE 544 WOOD FRAMING. Organization. Evaluation. Text ARCHITECTURE 544 WOOD FRAMING Prof. Dr. Ing. Peter von Buelow pvbuelow@umich.edu 1205c Art & Architecture Bldg. Lecture Topics : Course Structure Codes NDS Approach Sawn Lumber Engineering Properties Engineered