Here are some handy charts and
other useful information
updated
6-8-08
Mandrels
These are the sizes of tight tolerance rod stock I use for coiling wire.
It's water tempered, tool steel, drill rod stock.
My current sets are 86 rods for $15 an inch, See here.
Ring
Size
 inch
 mm
 Ring
Size
 inch
 mm
dia.
 circ.
 dia.
 circ.
 dia.
 circ.
 dia.
 circ.
1/2
.474
1.49
12.0
37.8
8
 .714
 2.24
 18.1
 57.0
1
.490
1.54
12.4
39.1
8 1/2
 .730
 2.29
 18.5
 58.2
1 1/2
.506
1.59
12.9
40.4
9
 .746
 2.34
 18.9
 59.5
2
.522
1.64
13.3
41.6
9 1/2
 .762
 2.39
 19.4
 60.8
2 1/2
.538
1.69
13.7
42.9
10
 .778
 2.44
 19.8
 62.1
3
.554
1.74
14.1
44.2
10 1/2
 .794
 2.49
 20.2
 63.3
3 1/2
.570
1.79
14.5
45.5
11
 .810
 2.55
 20.6
 64.6
4
.586
1.84
14.9
46.8
11 1/2
 .826
 2.60
 21.0
 65.9
4 1/2
.602
1.89
15.3
48.0
12
 .842
 2.65
 21.4
 67.2
5
.618
1.94
15.7
49.3
12 1/2
 .858
 2.70
 21.8
 68.5
5 1/2
.634
1.99
16.1
50.6
13
 .874
 2.75
 22.2
 69.7
6
.650
2.04
16.5
51.9
13 1/2
 .890
 2.80
 22.6
 71.0
6 1/2
.666
2.09
16.9
53.9
14
 .906
 2.85
 23.0
 72.4
7
.682
2.14
17.3
54.4
14 1/2
 .922
 2.90
 23.4
 73.7
7 1/2
.698
2.19
17.7
55.7
15
 .938
 2.95
 23.8
 74.9
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
 
Rod
Size
#
 
  
 
Rod
Size
#
 
inch
mm
  
inch
mm
.0625
1/16
1.58
  
.0938
3/32
2.38
.0630
52
1.60
  
.0950
41
2.41
.0660
51
1.67
  
.0970
40
2.46
.0690
50
1.75
  
.1010
38
2.57
.0720
49
1.83
  
.1060
36
2.69
.0750
48
1.91
  
.1094
7/64
2.77
.0770
47
1.96
  
.1100
34
2.79
.0782
5/64
1.99
  
.1120
33
2.84
.0790
46
2.01
  
.1150
32
2.92
.0810
45
2.06
  
.1250
1/8
3.18
.0850
44
2.15
  
.1270
30
3.23
.0880
43
2.24
  
.1406
9/64
3.57
.0920
42
2.34