Countersinks and Tapered Drills by the W. L. Fuller Company

You will find a complete list of C-Series Countersinks on the page titled Screw Dimensions. There are two approaches to drilling pilot holes for wood screws: Using a straight drill, either regular point, or brad-point, drill the pilot hole smaller than the shank size, but slightly larger than the root diameter of the threaded portion of the screw. This is a compromise in sizing, as the threaded portion will be about right, and installing the screw will force the shank into the upper portion of the pilot hole.  Using a tapered drill, drill the hole the same size as the shank size of the screw; the portion of the hole where the threads will be, will be tapered accordingly. The threaded portion will be correctly sized, and the shank will not have to be forced in nearly as much. In both cases, hole sizes need to be slightly larger in hardwoods, and slightly smaller in softwoods, for optimum results.  Screw Size  Drill Type  #3  #4  #5  #6  #7  #8  #9  #10  #12  #14  #16  #18  #20  #24  #28  Tapered, Hrdwd.  C4  C4  C5  C6  C7  C8  C9  C102  C12  C14  C169  C18  C20  C24  C287  Tapered, Sftwd.  C3  C3  C57  C5  C6  C7  C8  C92  C102  C1415  C1617  C1619  C18  C20  C286  Straight, Hrdwd.  C2  C2  C56  C57  C57  C5  C6  C129  C125  C1211  C143  C167  C247  C245  C286  Straight, Sftwd.  C2  C2  C56  C56  C56  C57  C5  C122  C129  C125  C145  C143  C243  C244  C285 Even after you make your basic decision (Tapered or Straight Drill bits), the table above might imply that you need two different countersinks for every screw size you want to work with. Choose the size that matches your usual application (hardwoods or softwoods), or choose the larger of the two choices (for hardwoods). As a practical matter, you can usually use a slightly smaller pilot drill with the countersink, than the prescribed size, without serious consequences. Hence you can choose the tool for use in hardwoods, and use a slightly smaller pilot drill for softwoods, in the same countersink, for the occasional softwood project. This table matches C-Series Countersinks with Tapered Drill Bits and Stop Collars. When using non-tapered bits, use the table above to choose your countersinks, then purchase from the table below. Buy a Countersink, plus your choice of Short-, Regular- or Long Length Tapered Drill Bit, and Stop Collars, from this table.  Stock # Dimensions  Screw Size Countersinks Short Drills Regular Drills Long Drills Stop Collars   Dia. x Pilot Hole             C3 1/4" x 3/32" #2       C3 $6.20 20000093 $2.65 20100093 $3.80 20200093 $7.85 11900250 $2.10 C4 5/16" x 7/64" #3, 4       C4 $6.20 20000109 $4.10  20100109 $3.90  20200109 $9.40  11900312 $2.15 C5 3/8" x 1/8" #5       C5 $5.60 20000125 $4.20 20100125 $3.80  20200125 $9.60  11900375 $2.30 C6 3/8" x 9/64" #6       C6 $5.60 20000140 $4.35 20100140 $4.05  20200140 $11.80  11900375 $2.30 C7 3/8" x 5/32" #7       C7 $5.60 20000156 $4.50 20100156 $4.05 20200156 $11.15 11900375 $2.30 C8 3/8" x 11/64" #8       C8 $5.60 20000171 $4.55  20100171 $4.25 20200171 $11.30 11900375 $2.30 C9 3/8" x 3/16" #9       C9 $5.60 20000187 $4.75 20100187 $4.45 20200187 $11.25 11900375 $2.30 C10 7/16" x 13/64" #10       C10 $6.20 20000203 $4.85 20100203 $4.65 20200203 $13.70 11900437 $2.55 C92 1/2" x 3/16" #9       C92 $6.20 20000187 $4.75  20100187 $4.45 20200187 $11.25 11900500 $2.60 C102 1/2" x 13/64" #10       C102 $6.20 20000203 $4.85  20100203 $4.65 20200203 $13.70 11900500 $2.60 C12 1/2" x 7/32" #12       C12 $6.20 20000218 $5.10  20100218 $4.95 20200218 $14.40 11900500 $2.60 C14 1/2 x 1/4" #14       C14 $6.20 20000250 $5.70 20100250 $5.45 20200250 $12.70 11900500 $2.60 C143 5/8" x 3/16" #10       C143 $8.30 20000187 $4.75 20100187 $4.45 20200187 $11.25 11900625 $3.10 C16 5/8" x 1/4" #16       C16 $8.30 20000250 $5.70 20100250 $5.45 20200250 $12.70 11900625 $3.10 C169 5/8" x 9/32" #16       C169 $8.30 20000281 $5.95 20100281 $7.00 20200281 $14.85 11900625 $3.10 C18 5/8" x 5/16" #18       C18 $8.30 20000312 $6.45 20100312 $7.70 20200312 $15.45 11900625 $3.10 C20 3/4" x 21/64" #20       C20 $10.95 20000328 $6.85 20100328 $8.40 20200328 $17.60 11900750 $3.20 C24 3/4" x 3/8" #24       C24 $10.95 20000375 $8.05 20100375 $10.05 20200375 $20.00 11900750 $3.20 C286 7/8" x 3/8" #28       C286 $14.00 20000375 $8.05 20100375 $10.05 20200375 $20.00 11900875 $3.30 C287 7/8" x 7/16" #28 Not Available * Not Available * Not Available *       C287 $14.00       11900875 $3.30 * denotes that no Tapered Drill is available in this diameter (7/16"). There are two ways to accomplish the hole for a #28 screw. The first method uses a C287 Countersink with a straight pattern 7/16" drill for the shank and a Tapered 3/8" drill, of the appropriate length, for the rest of the pilot hole. The second method uses a C286 Countersink with the appropriate length Tapered Drill for the length of the screw, then the shank area is over-bored with a 7/16"straight drill equipped with a stop collar. There is one Stop Collar of that size in the table above, #11900437. We are W.L. Fuller distributors. We stock the items in the table above; if you need a W.L. Fuller item we don't stock, just ask.