Component lead sizes

A through-hole -- many components (called "through-hole components") require a hole (a "through hole") for each pin. The part manufacturer should specify a "footprint" including the location and size of each hole. If there is no recommendation, common practice is:

round leads: add 6 mils to the nominal round lead diameter to get the recommended PCB hole diameter. Rectangular leads: find the lead diagonal (sqrt(x^2 + y^2)). Then add 6 mils to get the recommended PCB hole diameter. ( 6 mils ~= 0.15 mm )
"The component lead - hole clearance should be 0,4 mm" Seems large?
"The optimum pad diameter for a through-hole component is twice its finished hole diameter." 

Circuit Designers Companion 2nd Ed says: 0.15-0.3 clearance but some manufacturers need larger for autoplacement.. PTH holes pads can be smaller then NPTH, ie PTH 0.8mm hole pad can be 1.3-1.5mm, but NPTH should be around 2mm, larger holes need even more.  This is because the solder fixes to the hole plating in PTH for the connection whereas PTH relies on the actual pad.


 Part
Lead Measured at 
+ 0.15 
 + Clearance 0.3
Revised Hole Size (Finished PTH)
PTH Pad (Hole + 0.5 (min)
Pad x 
Pad y 
 Diode - Med Heavy (IN4004)  0.8  0.815  1.1  1.0  1.5    
 Diode - Signal  0.5  0.515  0.8  0.8  1.3    
 Cap - Small Ceramic  0.5   0.515  0.8  0.8  1.3    
 Cap - Larger Ceramic  0.6  0.615  0.9  0.9  1.4    
 Cap - Electro - Small  0.5-0.6 (0.6)    0.9  0.9  1.4    
 Cap - Tant - Small 0.5-0.6 (0.6)     0.9  0.9  1.4    
 Resistor - E12  0.55    0.85  0.8  1.3    
 Resistor - 1 up from E12 0.5-0.68 (0.68)     0.98  1.0  1.5    
 Trimpot Vert Small
 0.9    1.2  1.2  1.7    
               
 40 PDIP - Milled  0.52    0.82  0.8  1.3    
 40 PDIP - Cheap  0.6    0.9  0.9  1.4    
               
 SIP Pins Square  0.85  0.815  0.88  0.9  1.4    
 Machined Pin Headers  0.5  0.515  0.8  0.8  1.3    
 Term 5.08 spaced  0.93   1.23   1.2  2.0    
 Push Down Term  0.98   1.28   1.3  2.0    
               
 DEK623 RJ12 0.6     0.9  0.8 (I need the space this time around)  1.3    
 USB B Type 0.63    0.93   1.0  1.5    
               
 L7905CV, KA7905 0.9     1.2  1.2  1.8