1. Let’s Design a Box John Cobb www.treenshop.com www.treenshop.com/downloads/ john@treenshop.com 466-3973

2. 2 ‘Design’ Meaning In this context Design means determining all of the box’s measurements One can then make a dimensioned block diagram

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4. 4 Grain Orientation Boxes can be either End grain Side or face grain This discussion assumes end-grain or spindle grain

5. 5 Suppose we have a very large blank –10 inches square –36 inches long –A chunk of burl, for example That is, plenty large enough to make a box any reasonable size. How do we proceed?

6. 6 Select a Lid Type Over-fitting –Spigot is on the body –Easier to turn and get right In-fitting –Spigot is on the lid Let’s agree on a box with an over-fitting lid

7. 7 Box With Over-Fitting Lid

8. 8 Box With In-Fitting Lids

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10. 10 Face-Grain Box

11. 11 Diameter or Length? We can specify either (or both) Let’s specify diameter first.

12. 12 Select the Diameter Boxes with a diameter over 4 inches Uneasy to hold Difficult to take the lid off if there is a friction fit. BUT Boxes smaller than 2 inches diameter Have small tolerances Fitting the lid is error-prone

13. Let’s agree on about 3 inches in diameter or 75 millimeters

14. A TIP I always design using metric measurements as they are MUCH easier to work with. i.e. rounding to the nearest millimeter is easier than rounding to the nearest 64 th or 32 nd of an inch.

15. 15 So, Cut a Square 3 ¼ inches square and 36 inches long from our large block We now need to find the blank length.

16. 16 How Long Must the Blank Be? Decide on the relationship –Diameter to height

17. 17 Diameter vs Height There are many options –Diameter = height (square box) –Diameter = body height –Body Height 2/3 The Diameter –Body Height 3/4 The Diameter –Body Height 0.618 The Diameter –And many more …

18. 18 Select an option Let’s agree on body height = diameter This will be a tall box So body height = 75mm.

19. 19 Select a Proportioning Scheme There are many options: Golden mean or 0.618 the height Lid 1/3 and body 2/3 the height Lid 4/9 and body 5/9 the height Lid 3/7 and body 4/7 the height Something else entirely Avoid body and lid both ½ the height

20. 20 Select an option Let’s agree on using the golden mean –Body height = 0.618 the total height So, total height = 1.618 the body height Note that

21. 21 Some More Selections Specify the chucking waste at each end Specify the waste for the parting cut Specify the length of the spigot

22. 22 Our Specifications Let’s agree on the following –Waste at each end is 3mm (1/8) –Waste at parting cut is 4mm –Spigot length is 10 mm (3/8)

23. 23 Now Calculate! Body height is 0.618 total height –Total height = body height / 0.618 Body height is 75mm –Total height = 75/0.618 = 121.36 mm –Round Total height to 121mm

24. 24 What We Know So Far Diameter = 75mm Body height = 75mm Total height = 121mm

25. 25 Find the Lid Height Lid height = total height – body height –Lid height = 121 – 75 = 46mm

26. 26 Find the Blank Length Blank length is the sum of: –Total height –Total waste –Spigot length Note that the total waste is: –waste at each end + parting waste 3 + 3 + 4 = 10mm

27. 27 Find the Blank Length The blank length is: 121 + 10 + 10 = 141mm

28. 28 Check the findings Body height goal = 0.618 total height Body height ratio actual 75/121 = 0.62 waste at body end= 3 + body height = 75 + spigot length= 10 + parting waste= 4 + lid height= 46 + waste at lid end= 3 Total blank length = 141 3 + 75 + 10 + 4 + 46 +3 = 141

29. 29 The Remaining Dimensions Spigot inside and outside diameters Body inside diameter Body depth Lid inside diameter Lid depth

30. 30 Wall Thicknesses 1 ½ to 2mm are the minimums 2mm is about right for a spigot wall 2mm is a bit less than 3/32 inch Body and lid wall thickness must accommodate any decorations such as beads

31. 31 Select Wall Thicknesses Let’s agree on the following: –Spigot wall thickness = 2mm –Body and lid wall thicknesses – 4mm Allowing for a bead at the join

32. 32 Calculate Again! Body inside diameter = –Body outside diameter – 2 x (2mm + 4mm) = 75 – 12 = 63mm Spigot outside diameter = –Body inside diameter + 2 x 2mm = 63mm + 4 = 67mm Lid inside diameter = spigot diameter 67mm

33. 33 Specify End Thicknesses Let the body bottom thickness be 5mm Let the lid top thickness be 8mm –Allow for some decoration

34. More Calculation The depth of the body cavity is: body height + spigot length – end thickness 75 + 10 – 5 = 80mm The depth of the lid cavity is: Lid height - end thickness 46 – 8 = 38mm

35. 35 Mark for Parting From body chucking spigot: Body height + spigot length + + half parting waste 75 + 10 + 2 = 87mm From lid chucking spigot: Lid height + half parting waste 46 + 2 = 48mm These marks should coincide!

36. 36 We’re Done There is now available all information to make a dimensioned drawing

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38. 38 BREAK 10 MINUTE BREAK

39. 39 Variations Here are some variations on the straight box. Notice how close the dimensions in all of them are. They show several ways to get to the same result. The 'Straight Box With Body Height 3/4 The Diameter' is the only one that is noticeably different.

40. 40 ‘Square’ Straight Box Here is a design for a 48mm square box The height is equal to the diameter. It is proportioned using the golden mean i.e. about 2 to 5 lid height to total height.

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42. 42 Straight Box With Body Height 2/3 The Diameter This box is proportioned using the golden mean i.e. about 2 to 5 lid height to total height. Notice how close the dimensions are to the 'square' box seen previously.

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44. 44 Straight Box With Body Height 3/4 The Diameter This box is proportioned using the golden mean i.e. about 2 to 5 lid height to total height. Notice how close the dimensions are to the '2/3' box above. Also note the differences.

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46. 46 Straight Box With Body Height 0.618 The Diameter This box uses the golden mean throughout for proportioning. Notice how close the dimensions are to the 'square' box seen previously.

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48. 48 Observations The square box and the 2/3 box are nearly the same The square box and the 0.618 box are almost identical. The ¾ box is the only one that is significantly different.

49. 49 Another Design Method Specify the total height Specify the diameter Specify a proportion scheme ( Ex: We have a 2” square 24” long.)

50. 50 Example 1 Let’s agree on the following: The diameter shall be 48 mm The height shall be 3” or 75 mm The proportion factor shall be 0.618

51. 51 Now Calculate Body height = 0.618 x total height which is 0.618 x 75 = 46mm Lid height = 75 – 46 = 29mm Diameter = 48mm as specified

52. 52 Specify Other Measurements Waste at the ends = 3mm Waste at the parting cut = 4mm Spigot length = 10mm Bottom thickness = 5mm Lid top thickness = 6mm etc

53. 53 Now Make a Drawing Note that this design procedure is less complicated than the previous one.

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55. 55 Mixing the Two Methods With technique #2, suppose we specify that the body height is to be 2/3 the diameter and we also specify the height. In this case, we cannot also specify the diameter IF a proportion is also specified. Diameter must be allowed to be calculated.

56. 56 Example 2 Let’s agree on the following: The height shall be 3” or 75 mm The body height shall be 2/3 the diameter The proportion factor shall be 0.618

57. 57 Calculate Body height = 0.618 x 75 = 46mm Body height = 2/3 box diameter –Box diameter = (body height) / (2/3) = 69mm We can now calculate remaining dimensions (not shown)

58. 58 Other Proportions Several proportions besides the golden mean work 1 to 2 lid to body; height is 3 parts 3 to 4 lid to body; height is 7 parts 4 to 5 lid to body; height is 9 parts The reciprocals will sometimes work depending upon the design

59. 59 Other Proportions Thirds Rule of Thumb Measure from lid chucking spigot 1/3 the total length Mark for parting off For most lengths we use, it works well Totally accurate for exactly one length http://www.treenshop.com/Treenshop/ArticlesPages/RulesOfThumb_Article/Rul esOfThumb.htm

60. 60 Avoiding Errors The preceding methods are error-prone and tiresome I have found it best to make a spreadsheet Worth the effort if making a lot of boxes http://www.treenshop.com/downloads/ Lets_Design_A_Box.xls

61. 61 How To Save Some Money Suppose I hold my box blank between centers for roughing out. 4-prong center at the headstock Revolving center with a point at the tailstock

62. 62 Saving Some Money There will be about 10mm waste at the headstock and 5 to 6mm at the tailstock. That is 16mm waste If I part off with a 3/16” parting tool then there is an additional 6 to 8mm wasted. That’s a total of 24mm waste!

63. 63 Saving Some Money By holding the blank in a chuck for roughing and using a spigot chuck to turn it, there will be 3mm waste at each end. By parting with a thin parting tool, there will be about 4mm parting waste. That’s a total of 10mm waste. We save 14mm of wood!

64. 64 Saving Some Money Suppose we make 100 boxes using kingwood. Further suppose that kingwood is $40/bdft We save 100 x 14 = 1400mm (55 inches) by conserving waste

65. 65 Saving Some Money 55 inches of 3x3 is 3.44 board feet Each board foot is $40 Our savings are $137!

66. 66 Saving Some Money Its even better than that! Since the chucking spigots are not damaged on the end grain, we need not waste them. So our total waste can be as little as 4mm – where we part off

67. 67 The Lesson Careful design to minimize waste can result in serious savings! When designing, do not rough out expensive blanks between centers; include the chucking spigots in the design where possible

68. 68 Small Differences Small changes can make a major difference in appearance and visual appeal Check the form vigorously For a new design, consider making a prototype

69. 69 BREAK 10 MINUTE BREAK

70. 70 Needle Cases

71. 71 Designing Needle Cases and Crochet Hook Boxes Requires different design approach Must contain a specified amount

72. 72 Needle Cases Specify these measurements: Inside height Finial lengths (which may be unequal) Chucking and parting wastes Spigot length.

73. 73 Needle Cases Let’s agree on these items: Inside height is to be 75mm Both finials are to be 13mm Waste is to be 3mm at each end Parting waste is 4mm The spigot length is to be 16mm

74. 74 Needle Cases Calculate the outside height as: Inside height + lid finial length + body finial length Outside height = 75 + 13 + 13 = 101mm

75. 75 Needle Cases Specify the proportionality constant. Let the proportionality constant be 0.618 – the golden mean

76. 76 Needle Cases Calculate the body outside height and the lid outside height as: Body outside height = 0.618 * outside height = 0.618 * 101 = 62mm Lid outside height = 101 – 62 = 39mm

77. 77 Needle Cases Calculate inside heights as: Body inside height = body outside height – body finial length Body inside height = 62 – 13 = 49mm Lid inside height = lid outside height – lid finial length Lid inside height = 39 – 13 = 26mm Note that this dimension must be > spigot length (16mm)

78. 78 Needle Cases Calculate the depth of the hole that must be drilled/turned in the body as Depth = body inside length + spigot length Depth = 49 + 16 = 65mm

79. 79 Needle Cases Calculate the total body length, which includes the length of the spigot, as outside body length + spigot length Total body length = 62 + 16 = 78mm

80. 80 Needle Cases Calculate the length of the turning blank as Blank length = total outside height + spigot length + waste Blank length = 101 + 16 + 10 = 127mm

81. 81 Needle Cases Specify the inside diameter and calculate the spigot outside diameter the outside diameter: Let the inside diameter be 10mm. Let the thickness of the spigot be 2mm Let the wall thickness of the lid also be 2mm Spigot outside diameter = 10 + 2*2 = 14mm Box outside diameter = 10 + 2*2 + 2*2 = 18mm

82. 82 Needle Cases Mark the blank for parting off: From the lid chucking spigot: Total lid height + half parting waste = 39 + 2 = 41mm From the body chucking spigot: Total body height + half parting waste = 78 + 2 = 80mm Note that 41 + 80 +3 + 3 = 127 (blank length)

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84. 84 Not Covered Boxes with in-fitting lids Stacked, multi-tier boxes Tall 4-piece boxes Face grain boxes Boxes with threaded lids/spigots

85. 85 Tall Box in 4 Parts

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87. 87 THE END! Use these examples and Change the assumptions Change the proportions To create your own designs

88. 88 Contact Info John Cobb www.treenshop.com www.treenshop.com/downloads/ john@treenshop.com 466-3973