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Drill Sizes

 

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Note: dimensions below are in inches.

Diameter Drill Size Application
0.012 83 Small vias - Do not use unnecessarily
82
81
80
79
78
77
0.020 76 Preferred vias
75
74
73
72
71
0.028 70 Integrated Circuits ( DIP ) and TO-92
Small pots signal diodes
69
68
0.032 67
0.033 66

Small resistors and capacitors LEDs

Headers and small connectors

0.035 65
0.036 64
0.037 63
0.038 62
0.039 61 TO-220 1N4001 Large Resistors
0.040 60
0.041 59 Large Capacitors 3A-Rectifiers
Small Bridge Rectifiers
0.042 58
0.043 57
0.046 56 Small Terminal Blocks
TO-3 and other large semiconductors
Small Transformers Relays
0.052 55
0.055 54
0.059 53 10A Terminal Blocks
.156" spaced connectors
Fuse Holders
0.063 52
0.067 51  
0.070 50  
0.073 49  
0.076 48  
0.078 47  
0.081 46  
0.082 45  
0.086 44  
0.089 43  
0.093 42  
0.096 41  
0.098 40 Mounting holes for DB-25 type connectors
0.099 39  
0.101 38  
0.104 37  
0.106 36  
0.110 35  
0.111 34  
0.113 33  
0.116 32  
0.120 31  
0.128 30  
0.136 29  
0.140 28  
0.144 27  
0.147 26  
0.149 25  
0.152 24  
0.154 23  
0.157 22  
0.159 21  
0.161 20  
0.166 19  
0.169 18  
0.173 17  
0.177 16  
0.180 15  
0.182 14  
0.185 13  
0.189 12  
0.191 11  
0.193 10  
0.196 9  
0.199 8  
0.201 7  
0.204 6  
0.205 5  
0.209 4  
0.213 3  
0.221 2  
0.228 1  

Notes (borrowed from Eddy Electronics in Canada)

Pad and via size: One should maintain the largest practical annular ring to insure a good mechanical, as well as electrical and thermal connection. There is a wide variety of pad sizes and shapes available to accomplish this. Octagonal pads are far superior to round.
Eddy's rule: the pad or via size should be 50% greater in diameter than the diameter of the hole.

Eddy's Inverse: the hole should be 2/3 the diameter of the pad.

Plating through and tolerances: Hole sizes should be specified as finished hole sizes. This compensates for the loss of diameter in plating through the hole; the hole will be around .002" smaller than drilled. This figure represents an average that can vary by as much as 30%. Larger holes will take more plating than small ones as a rule and holes near the outside of a panel will also take more copper. On the other side of the equation, the plating thickness will be greater than the .002" decrease in hole diameter. Due to etch-back and internal stress, you may have as much as .002" copper thickness. This thickness on both sides of the hole adds up to .004" total copper, yet the hole is only .002" smaller.

Obviously, one needs to be careful in considering hole sizes, as there are a great many variables including accuracy of hole location and tolerances within the component to be placed.

A good practice is to allow .005" extra hole diameter to accommodate all of these variables. This also allows de-soldering of defective parts during repair.

Author : Unknown Editor

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