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Thread: Screw pilot drill charts

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    mklotz mklotz's Avatar
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    Screw pilot drill charts

    Not being an accomplished woodworker, I was always puzzled by what pilot drill I should use for a given screw size. I ran across the attached chart somewhere and, finding it useful, thought I should pass it along to others puzzled by the mysteries of the brown stuff.

    Later on I ran across a similar chart for self-tapping sheet metal screws and have included that as well.



    Code:
    			WOOD SCREW DATA
    
    N = NOMINAL SIZE
    T = THREADS PER INCH
    D = DIAMETER OF UNTHREADED ROOT (in)
    B = BODY DRILL SIZE (in)
    S = PILOT DRILL SIZE IN SOFT WOOD (in)
    H = PILOT DRILL SIZE IN HARD WOOD (in)
    
     N	 T	  D		B	 S	 H	  B	  S	  H
    -------------------------------------------------------------------------------
     0	32	.060		52	75	66
     1	28	.073		47	71	57
     2	26	.086		42	65	54
     3	24	.099		37	58	53
     4	22	.112		32	55	51	1/8	1/16	5/64
     5	20	.125		30	53	47	9/64	5/64	3/32
     6	18	.138		27	52	44	9/64	5/64	3/32
     7	16	.151		22	51	39	5/32	3/32	7/64
     8	15	.164		18	48	35	11/64	3/32	7/64
     9	14	.177		14	45	33	3/16	7/64	1/8
    10	13	.190		10	43	31	3/16	7/64	1/8
    11		.203		4	40	29
    12	11	.216		2	38	25	7/32	1/8	5/32
    14	10	.242		D	32	14
    16	 9	.268		I	29	10
    18	 8	.294		N	26	6
    20	 8	.320		P	19	3
    24	 7	.372		V	15	D
    
    
    Recommended Drill Sizes for Self-Tapping Screws (Sheet Metal)
    
    N = Number
    T = Threads per inch
    OD = Outside Diameter
    A = Drill for heavy metals
    B = Drill for light metals
    
    N      T    OD   A   B
    2     32  .086  49  49
    4     24  .112  41  41
    5     20  .125  36  36
    6     20  .138  32  32
    7     19  .151  30  30
    8     18  .164  28  29
    10    16  .190  20  21
    12    14  .216  13  14
    1/4   14  .250  3   4
    5/16  12  .313  I   H
    3/8   12  .375  R   Q


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  2. The Following User Says Thank You to mklotz For This Useful Post:

    bustre (04-15-2017)

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