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Solid Counterbores and Step Drills

Inch Size 3 Flute Capscrew Counterbores

High speed steel, for socket cap screws.
3 Flute capscrew counterbores have larger pilots than 2 Flute solid counterbores.
With straight shanks.
Quantity Price Model Description Screw Size Pilot Diam. Cutter Diam. Shank Diam.

$9.10 CBCS-5
#5 Capscrew Counterbore, 3 Flute, HSS #5 .141" .221" 3/16"

$9.10 CBCS-6
#6 Capscrew Counterbore, 3 Flute, HSS #6 0.15" 0.242 7/32"

$9.10 CBCS-8
#8 Capscrew Counterbore, 3 Flute, HSS #8 11/64" 19/64 1/4"

$10.30 CBCS-10
#10 Capscrew Counterbore, 3 Flute, HSS #10 13/64" 21/64 5/16"

$12.05 CBCS-1/4
1/4" Capscrew Counterbore, 3 Flute, HSS 1/4" 9/32" 13/32 3/8"

$14.15 CBCS-5/16
5/16" Capscrew Counterbore, 3 Flute, HSS 5/16" 11/32" 1/2 7/16"

$15.60 CBCS-3/8
3/8" Capscrew Counterbore, 3 Flute, HSS 3/8" 13/32" 19/32 1/2"

$18.65 CBCS-7/16
7/16" Capscrew Counterbore, 3 Flute, HSS 7/16" 15/32" 11/16 1/2"

$20.40 CBCS-1/2
1/2" Capscrew Counterbore, 3 Flute, HSS 1/2" 17/32" 25/32 1/2"

$20.40 CBCS-1/2A
1/2" Capscrew Counterbore, 3 Flute, HSS (3/4" Shank) 1/2" 17/32" 25/32 3/4"

$29.90 CBCS-5/8
5/8" Capscrew Counterbore, 3 Flute, HSS 5/8" 21/32" 31/32 3/4"

$41.60 CBCS-3/4
3/4" Capscrew Counterbore, 3 Flute, HSS 3/4" 13/16" 1 3/16 1"

Metric Capscrew Counterbores

High speed steel, for metric socket cap screws.
Most sizes have 3 flutes, but some may have 4 flutes.
Straight shank, except for some of the largest sizes, as specified.
Quantity Price Model Description Screw Size Pilot Diam. Cutter Diam. Shank Diam.

$10.40 CBCS-M3
3mm HS Capscrew Counterbore 3mm 3.4mm 6mm .2185"

$11.30 CBCS-M4
4mm HS Capscrew Counterbore 4mm 4.5mm 8mm .3122"

$14.50 CBCS-M5
5mm HS Capscrew Counterbore 5mm 5.5mm 10mm .3747"

$16.00 CBCS-M6
6mm HS Capscrew Counterbore 6mm 6.6mm 11mm .4371"

$16.00 CBCS-M8
8mm HS Capscrew Counterbore 8mm 9mm 15mm .4996"

$17.60 CBCS-M10
10mm HS Capscrew Counterbore 10mm 11mm 18mm .4996"

$19.10 CBCS-M12
12mm HS Capscrew Counterbore 12mm 14mm 20mm .4996"

$25.30 CBCS-M14
14mm HS Capscrew Counterbore, TS 14mm 15mm 24mm 2 Morse Taper

$30.10 CBCS-M16
16mm HS Capscrew Counterbore, SS 16mm 17mm 26mm 1"

$30.10 CBCS-M16T
16mm HS Capscrew Counterbore, TS 16mm 17mm 26mm 2 Morse Taper

Capscrew Counterbores Sets

High speed steel, for socket cap screws.
Larger pilots than 2-flute solid counterbores. Straight shank
Quantity Price Model Description Sizes

$33.50 CBCS-ST11
Capscrew Counterbore Set, 3 flutes, #6 - 1/4" #6, 8, 10, 1/4

$47.50 CBCS-ST12
Capscrew Counterbore Set, 3 flutes, 1/4" - 1/2" 1/4, 5/16, 3/8, 1/2

$77.00 CBCS-ST13
Capscrew Counterbore Set, 3 flutes, #6 - 1/2" #6, 8, 10, 1/4, 5/16, 3/8, 1/2

$63.80 CBCS-ST21
Capscrew Counterbore Set, 4 flutes, 3mm-10mm 3mm,4mm, 5mm, 6mm, 8mm, 10mm

2 Flute Solid Counterbores

2 Flute. High Speed Steel. For socket cap screws
Quantity Price Model Description Pilot/Screw Size Cutting Size Overall Length

$8.25 CB2-3
#3 Solid Counterbore, 2 Flute, HSS .098/#3 .176" 2 1/2"

$7.15 CB2-4
#4 Solid Counterbore, 2 Flute, HSS .111/#4 0.198 2 5/8

$7.75 CB2-5
#5 Solid Counterbore, 2 Flute, HSS .124/#5 0.22 2 5/8

$8.00 CB2-6
#6 Solid Counterbore, 2 Flute, HSS .137/#6 0.241 2 5/8

$8.50 CB2-8
#8 Solid Counterbore, 2 Flute, HSS .163/#8 0.285 2 3/4

$9.15 CB2-10
#10 Solid Counterbore, 2 Flute, HSS .189/#10 0.328 2 7/8

$10.20 CB2-12
#12 Solid Counterbore, 2 Flute, HSS .215/#12 0.372 3

$14.70 CB2-1/4
1/4" Solid Counterbore, 2 Flute, HSS 1/4" 13/32 3 5/8

$15.40 CB2-5/16
5/16" Solid Counterbore, 2 Flute, HSS, with 15/32 CUT 5/16" 15/32 4

$13.40 CB2-5/16-A
5/16" Solid Counterbore, 2 Flute, HSS, with 31/64 CUT 5/16" 31/64 4

$17.60 CB2-3/8
3/8" Solid Counterbore, 2 Flute, HSS 3/8" 19/32 4 3/8

$19.90 CB2-7/16
7/16" Solid Counterbore, 2 Flute, HSS 7/16" 21/32 4 3/4

$21.60 CB2-1/2
1/2" Solid Counterbore, 2 Flute, HSS 1/2" 25/32 5 1/8

Unibit Step Drills

High speed steel. For cutting thin materials such as sheet metal.
One tool will cut multiple hole sizes, reducing toolbox clutter.
Self-starting. Easy to sharpen tip. Shank has 3 flats.
Made in USA by Irwin Unibit.
Quantity Price Model Description No. of Hole Sizes Hole Sizes (Increment) Shank Size Length Step Thickness

$22.10 UNI-1
#1 Unibit Step Drill 13 1/8" to 1/2" (1/32") 1/4" 1/8"

$22.10 UNI-2
#2 Unibit Step Drill 6 3/16" to 1/2" (1/16") 1/4" 3/8"

$39.80 UNI-3
#3 Unibit Step Drill 9 1/4" to 3/4" (1/16") 3/8" 1/8"

$47.10 UNI-4
#4 Unibit Step Drill 12 3/16" to 7/8" (1/16") 3/8" 1/8"

$83.50 UNI-5
#5 Unibit Step Drill 10 1/4" to 1-3/8" (1/8") 1/2" 1/8"

Style 371 Step Drills for Cap Screw Clearance

Style 371. For Drilling and Counterboring Cap Screw Clearance Holes.
High Speed Steel.
Jobbers length (except 1/2 and 5/8, which are shorter).
Easily resharpened. Does 2 jobs in a single pass.
Made in USA.
Quantity Price Model Description Minor Diameter Major Diameter Step Length Flute Length Overall Length

$12.80 DRST371-4
#4 371 Step Drill for Capscrew Clearance 0.136 7/32 3/8 2 1/2 3 3/4

$13.50 DRST371-5
#5 371 Step Drill for Capscrew Clearance 0.141 No. 1 (.228") 3/8 2 5/8 3 7/8

$14.30 DRST371-6
#6 371 Step Drill for Capscrew Clearance 0.150 1/4 1/2 2 3/4 4

$16.35 DRST371-8
#8 371 Step Drill for Capscrew Clearance 0.178 L (.290") 1/2 2 15/16 4 1/4

$17.90 DRST371-10
#10 371 Step Drill for Capscrew Clearance 0.204 Q (.332") 5/8 3 7/16 4 3/4

$20.65 DRST371-1/4
1/4" 371 Step Drill for Capscrew Clearance 9/32 13/32 11/16 3 7/8 5 1/4

$27.40 DRST371-5/16
5/16" 371 Step Drill for Capscrew Clearance 11/32 1/2 3/4 4 1/2 6

$43.80 DRST371-3/8
3/8" 371 Step Drill for Capscrew Clearance 13/32 19/32 7/8 5 3/16 7 1/8

$52.30 DRST371-7/16
7/16" 371 Step Drill for Capscrew Clearance 15/32 11/16 1 5 5/8 7 5/8

$72.10 DRST371-1/2
1/2" 371 Step Drill for Capscrew Clearance 17/32 25/32 1 3 1/4 5 1/8

$96.30 DRST371-5/8
5/8" 371 Step Drill for Capscrew Clearance 21/32 31/32 1 3 7/8 5 7/8

Style 372 Step Drills for Flat Head Screws

Style 372. For Drilling and Countersinking 82° Flat Head Screw Clearance Holes.
High Speed Steel. Jobbers length (except 7/16 and 1/2, which are shorter).
Easily resharpened. Does 2 jobs in a single pass.
Made in USA
Quantity Price Model Description Minor Diameter Major Diameter Step Length Flute Length Overall Length

$13.80 DRST372-4
#4 372 Step Drill for Flat Head Screws 0.116 15/64 3/8 2-5/8 3 7/8

$14.45 DRST372-5
#5 372 Step Drill for Flat Head Screws 0.128 F 3/8 2-7/8 4 1/8

$15.15 DRST372-6
#6 372 Step Drill for Flat Head Screws 0.142 9/32 1/2 2-15/16 4 1/4

$17.90 DRST372-8
#8 372 Step Drill for Flat Head Screws 0.169 Q 1/2 3-7/16 4 3/4

$19.50 DRST372-10
#10 372 Step Drill for Flat Head Screws 0.196 W 5/8 3-3/4 5 1/8

$24.14 DRST372-1/4
1/4" 372 Step Drill for Flat Head Screws 0.257 1/2 11/16 4-13/16 6 5/8

$37.85 DRST372-5/16
5/16" 372 Step Drill for Flat Head Screws 0.320 5/8 3/4 5-3/16 7 1/8

$52.50 DRST372-3/8
3/8" 372 Step Drill for Flat Head Screws (limited quantity at this length) 0.383 3/4 7/8 5-5/8 7 5/8

$68.35 DRST372-7/16
7/16" 372 Step Drill for Flat Head Screws 0.446 13/16 1 3-3/8 5 1/4*

$75.40 DRST372-1/2
1/2" 372 Step Drill for Flat Head Screws 0.510 7/8 1 3-1/2 5 1/2*

Style 370 Step Drills for Holes-To-Be-Tapped

Style 370. For Drilling 45 degree Chamfered Holes To-Be-Tapped.
High Speed Steel. Jobbers length.
Easily resharpened. Does 2 jobs in a single pass.
Made in USA
Quantity Price Model Description Minor Diameter Major Diameter Step Length Flute Length Overall Length

$12.10 DRST370-4-40
4-40 370 Step Drill for holes to tap 0.089 .1285" 3/8 1 5/8 2 3/4

$12.75 DRST370-5-40
5-40 370 Step Drill for holes to tap 0.101 9/64 1/2 1 3/4 2 7/8

$12.90 DRST370-6-32
6-32 370 Step Drill for holes to tap 0.109 5/32 1/2 2 3 1/8

$13.25 DRST370-8-32
8-32 370 Step Drill for holes to tap 0.136 3/16 1/2 2 5/16 3 1/2

$13.45 DRST370-8-36
8-36 370 Step Drill for holes to tap 0.136 3/16 1/2 2 5/16 3 1/2

$14.10 DRST370-10-24
10-24 370 Step Drill for holes to tap 0.152 1/4 5/8 2 3/4 4

$14.10 DRST370-10-32
10-32 370 Step Drill for holes to tap 0.161 1/4 5/8 2 3/4 4

$16.35 DRST370-12-24
12-24 370 Step Drill for holes to tap 0.179 9/32 11/16 2 15/16 4 1/4

$17.35 DRST370-1/4-20
1/4-20 370 Step Drill for holes to tap 0.204 21/64" 13/16 3 5/16 4 5/8

$17.65 DRST370-1/4-28
1/4-28 370 Step Drill for holes to tap 0.218 21/64" 13/16 3 5/16 4 5/8

$19.80 DRST370-5/16-18
5/16-18 370 Step Drill for holes to tap 0.261 13/32 15/16 3 7/8 5 1/4

$20.05 DRST370-5/16-24
5/16-24 370 Step Drill for holes to tap 0.272 13/32 15/16 3 7/8 5 1/4

$26.15 DRST370-3/8-16
3/8-16 370 Step Drill for holes to tap 0.316 31/64 1 4 3/8 5 7/8

$26.65 DRST370-3/8-24
3/8-24 370 Step Drill for holes to tap 0.339 31/64 1 4 3/8 5 7/8

$45.60 DRST370-7/16-14
7/16-14 370 Step Drill for holes to tap 0.375 17/32 1 1/16 4 13/16 6 5/8

$45.60 DRST370-7/16-20
7/16-20 370 Step Drill for holes to tap 0.39 17/32 1 1/16 4 13/16 6 5/8

$52.65 DRST370-1/2-13
1/2-13 370 Step Drill for holes to tap 0.437 5/8" 1 1/16 5 3/16 7 1/8

$53.30 DRST370-1/2-20
1/2-20 370 Step Drill for holes to tap 0.452 5/8" 1 1/16 5 3/16 7 1/8

$66.35 DRST370-5/8-11
5/8-11 370 Step Drill for holes to tap 0.531 3/4 1 1/16 5 5/8 7 5/8