1. Let’s Design a Box John Cobb www.treenshop.com

2. MAIN TOPICS Making a working drawing An easier way Variations
Design choices & arithmetic
An easier way
Variations
Rule of Thirds

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

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

7. 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?

8. a box with an over-fitting lid
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

9. Box With Over-Fitting Lid

10. Box With In-Fitting Lids

11. Box With In-Fitting Lids
Show African Mahogany cigar box with in-fitting lid.

12. Face-Grain Box

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

14. Select the Diameter BUT 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

15. Let’s agree on about 3 inches in diameter or 75 millimeters15

16. 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 64th or 32nd of an inch.
There are 25.4mm in 1 inch 16

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

18. How Long Must the Blank Be?
Can specify it
Or derive it – let’s derive it
Decide on the relationship
Diameter to height

19. Diameter vs Height There are many options
Height = Diameter (square box)
Body Height = Diameter (tall box)
Body Height = 2/3 The Diameter
Body Height = 3/4 The Diameter
Body Height = The Diameter
And many more …

20. Select an option Let’s agree on body height = diameter
This will be a tall box
So body height = 75mm.
Show 3 inch tall box in huon pine by Richard Raffan

21. Select a Proportioning Scheme
There are several options:
Golden mean or the height
Lid 1/3 and body 2/3 the height
Lid 4/9 and body 5/9 the height
Something else entirely
Avoid body and lid both ½ the height
Show Richard Raffan’s 3 inch mosque box in shee oak. Explain why it looks OK.
Show my mosque box – it does not look like 1 to 1 but it is

22. Select an option Let’s agree on using the golden mean
Body height = the total box height
So, total box height = the body height
Note that

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

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

25. Now Calculate! Body height is 0.618 total height Body height is 75mm
Total height = 75 / = mm
Round Total height to 121mm

26. What We Know So Far Diameter = 75mm Body height = 75mm (bottom part)
Total height = 121mm

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

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

29. Find the Blank Length
The blank length is:
= 141mm

30. 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
= 141

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

32. 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

33. 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

34. Calculate Again! Body inside diameter = Spigot outside 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

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

36. More Calculation The depth of the body cavity is:
body height + spigot length – end thickness
– 5 = 80mm
The depth of the lid cavity is:
Lid height - end thickness
46 – 8 = 38mm
(Must be greater than the spigot length)

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

38. Point out the two critical measurements for turning:
Parting distance from either end
Spigot length

39. We’re Done
There is now available all information to make a dimensioned drawing
(What a pain in the …)
Use a spreadsheet!
One is provided at
“Lets_Design_a_Box.xls”

40. 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.

44. This gives a square box if the proportioning scheme is also 0.618

45. The ¾ box is the only one that is significantly different.
Observations
The square box, the 2/3 box
and the box
are nearly the same
The ¾ box is the only one that is significantly different.

46. Another Design Method Specify the total height Or blank length
Specify the diameter
Specify a proportion scheme
( Ex: We have a 2” square 24” long.)
This is a more normal case.
One usually has a turning square and so the diameter is mostly determined.
So specify it and then specify the height and the proportion.

47. Body height is 96% the diameter
Proportions are 0.613

48. 1/3 the total length between spigots
Thirds Rule of Thumb
Measure from lid chucking spigot
1/3 the total length between spigots
Mark for parting off
For most lengths we use, it works well
and the proportions will be near 0.618
Totally accurate for exactly one length
Is on my website in the Articles pages: “Rules of Thumb”
Keep the spigot length about 3/8” or 10mm and use a narrow parting tool.

49. Not the same measurements as the example I showed which was 100mm between the chucking spigots

50. 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
Lets_Design_A_Box.xls

51. 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

52. 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!

53. 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!
Show with a square blank in a chuck with shark jaws.
Show revolving center with leather washer for support

54. 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

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

56. 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

57. 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
Show the 70mm buckeye burl box as an example.

58. 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
Show the thuya burl dome box. Body = 47; lid = 30; height = 77; proportions
The dome looks too small for the form. Maybe 4 to 5 would be more attractive.
The color is a contributor to this.
Show the maple dome box. Body = 45; lid = 45; height = 90; 1 to 2 proportions
The size of the dome looks better to me but could be a bit shorter.
4 to 5 proportions would give: body = 50; lid = 40; height = 90

59. Not Covered Boxes with in-fitting lids Stacked, multi-tier boxes
Tall 4-piece boxes
Face grain boxes
Needle cases & crochet hook boxes

60. Tall Box in 4 Parts Not covered but added as an extra.
Show maple tall box and mahogany tall box with finial

63. ON THE WEB On my downloads page: www.treenshop.com/downloads/
This presentation
TEW_BoxDesign_1.pps
The handouts
TEW_BoxDesign_1_Handouts.pps
The spreadsheet
Lets_Design_a_Box.xls

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

65. Contact Info
John Cobb