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Cobalt Drill Bit

Cobalt drill bits, made from heat resistant cobalt steel are heavy duty construction and made to NAS Type J aircraft specifications. Used for drilling holes in hard, tough materials such as stainless steel, titanium high temperature and high strength alloys. High red hardness of cobalt permits speeds 30% greater than HSS drills.

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Fractional Sizes
Wire Sizes
Letter Sizes
Drill Feeds & Speeds

Fractional Sizes

Fractional SizesCobalt Drill Bit

Size	Decimal Equivalent	Flute Length	Overall Length
1/16	0.0625	7/8	1 7/8
5/64	0.0781	1	2
3/32	0.0938	1 1/4	2 1/4
7/64	0.1094	1 1/2	2 5/8
1/8	0.1250	1 5/8	2 3/4
9/64	0.1406	1 3/4	2 7/8
5/32	0.1563	2	3 1/8
11/64	0.1719	2 1/8	3 1/4
3/16	0.1875	2 5/16	3 1/2
13/64	0.2031	2 7/16	3 5/8
7/32	0.2188	2 1/2	3 3/4
15/64	0.2344	2 5/8	3 7/8
1/4	0.2500	2 3/4	4
17/64	0.2656	2 7/8	4 1/8
9/32	0.2813	2 15/16	4 1/4
19/64	0.2969	3 1/16	4 3/8
5/16	0.3125	3 3/16	4 1/2
21/64	0.3281	3 5/16	4 5/8
11/32	0.3438	3 7/16	4 3/4
23/64	0.3594	3 1/2	4 7/8
3/8	0.3750	3 5/8	5
25/64	0.3906	3 3/4	5 1/8
13/32	0.4063	3 7/8	5 1/4
27/64	0.4219	3 15/16	5 3/8
7/16	0.4375	4 1/16	5 1/2
29/64	0.4531	4 3/16	5 5/8
15/32	0.4688	4 5/16	5 3/4
31/64	0.4844	4 3/8	5 7/8
1/2	0.5000	4 1/2	6

All dimensions are in inches.

Wire Sizes

Wire SizesCobalt Drill Bit

Size	Decimal Equivalent	Flute Length	Overall Length
1	0.2280	2 5/8	3 7/8
2	0.2210	2 1/2	3 7/8
3	0.2130	2 1/2	3 3/4
4	0.2090	2 1/2	3 3/4
5	0.2055	2 1/2	3 3/4
6	0.2040	2 1/2	3 3/4
7	0.2010	2 7/16	3 5/8
8	0.1990	2 7/16	3 5/8
9	0.1960	2 7/16	3 5/8
10	0.1935	2 7/16	3 5/8
11	0.1910	2 5/16	3 1/2
12	0.1890	2 5/16	3 1/2
13	0.1850	2 5/16	3 1/2
14	0.1820	2 3/16	3 3/8
15	0.1800	2 3/16	3 3/8
16	0.1770	2 3/16	3 3/8
17	0.1730	2 3/16	3 3/8
18	0.1695	2 1/8	3 1/4
19	0.1660	2 1/8	3 1/4
20	0.1610	2 1/8	3 1/4
21	0.1590	2 1/8	3 1/4
22	0.1570	2	3 1/8
23	0.1540	2	3 1/8
24	0.1520	2	3 1/8
25	0.1495	1 7/8	3
26	0.1470	1 7/8	3
27	0.1440	1 7/8	3
28	0.1405	1 3/4	2 7/8
29	0.1360	1 3/4	2 7/8
30	0.1285	1 5/8	2 3/4
31	0.1200	1 5/8	2 3/4
32	0.1160	1 5/8	2 3/4
33	0.1130	1 1/2	2 5/8
34	0.1110	1 1/2	2 5/8
35	0.1100	1 1/2	2 5/8
36	0.1065	1 7/16	2 1/2
37	0.1040	1 7/16	2 1/2
38	0.1015	1 7/16	2 1/2
39	0.0995	1 3/8	2 3/8
40	0.0980	1 3/8	2 3/8
41	0.0960	1 3/8	2 3/8
42	0.0935	1 1/4	2 1/4
43	0.0890	1 1/4	2 1/4
44	0.0860	1 1/8	2 1/8
45	0.0820	1 1/8	2 1/8
46	0.0810	1 1/8	2 1/8
47	0.0785	1	2
48	0.0760	1	2
49	0.0730	1	2
50	0.0700	1	2
51	0.0670	1	2
52	0.0635	7/8	1 7/8
53*	0.0595	7/8	1 7/8
54*	0.0550	7/8	1 7/8
55*	0.0520	7/8	1 7/8
56*	0.0465	3/4	1 3/4
57*	0.0430	3/4	1 3/4
58*	0.0420	11/16	1 5/8
59*	0.0410	11/16	1 5/8
60*	0.0400	11/16	1 5/8

*Not Split Point
All dimensions are in inches.

Letter Sizes

Letter SizesCobalt Drill Bit

Size	Decimal Equivalent	Flute Length	Overall Length
A	0.2340	2 5/8	3 7/8
B	0.2380	2 3/4	4
C	0.2420	2 3/4	4
D	0.2460	2 3/4	4
E	0.2500	2 3/4	4
F	0.2570	2 7/8	4 1/8
G	0.2610	2 7/8	4 1/8
H	0.2660	2 7/8	4 1/8
I	0.2720	2 7/8	4 1/8
J	0.2770	2 7/8	4 1/8
K	0.2810	2 15/16	4 1/4
L	0.2900	2 15/16	4 1/4
M	0.2950	3 1/16	4 3/8
N	0.3020	3 1/16	4 3/8
O	0.3160	3 3/16	4 1/2
P	0.3230	3 5/16	4 5/8
Q	0.3320	3 7/16	4 3/4
R	0.3390	3 7/16	4 3/4
S	0.3480	3 1/2	4 7/8
T	0.3580	3 1/2	4 7/8
U	0.3680	3 5/8	5
V	0.3770	3 5/8	5
W	0.3860	3 3/4	5 1/8
X	0.3970	3 3/4	5 1/8
Y	0.4040	3 7/8	5 1/4
Z	0.4130	3 7/8	5 1/4

All dimensions are in inches.

Drill Feeds & Speeds

Material	Hardness	Drill Type	Point Style	Point Angle	Speed (SFM)	Feed	Coolant
Aluminum / Aluminum Alloys	-	High Helix	Standard	118°	200-300	Medium to Heavy	Water Soluble
Aluminum Bronze	-	High Helix	Standard	118°	50-100	Medium to Heavy	Water Soluble
Brass, Free Machining	-	Low Helix	Standard	118°	100-250	Medium to Heavy	Water Soluble
Bronze, Soft Medium	Below 200	General Purpose	Standard	118°	70-150	Medium to Heavy	Water Soluble
Bronze, High Tensile	-	Low Helix or Half RD	Standard	118°	50-100	Medium to Heavy	Water Soluble
Copper / Copper Alloys	-	General Purpose	Standard	118°	100-200	Medium	Water Soluble
High Temp Alloys, Cobalt Base	180-300	Cobalt	Split Point	135°	5-20	Medium	Activated Oils
High Temp Alloys, Iron Base	180-300	Cobalt	Split Point	135°	5-20	Medium	Activated Oils
High Temp Alloys, Nickel Base	180-300	Nitro® or Cobalt	Split Point	135°	5-15	Medium	Activated Oils
Iron, Soft Case	Up to 150	Heavy Duty or Nitro®	Split Point	135°	75-150	Medium	Dry / Air
Iron, Medium Case	150-250	Heavy Duty or Nitro®	Split Point	135°	50-100	Medium	Dry / Air
Iron, Hard Case	Over 250	Carbide	Standard	118°	40-75	Light to Medium	Dry / Air
Plastic & Related Materials	-	Low Helix	Low Angle	90°	100-200	Medium to Heavy	Dry / Air
Steel, Low Carbon Alloy	125-275	General Purpose	Standard	118°	50-70	Medium	Water Soluble
Steel, Medium Carbon Alloy	275-325	Heavy Duty or Nitro®	Split Point	135°	40-55	Medium	Water Soluble
Steel, High Carbon Alloy	Over 325	Cobalt	Split Point	135°	30-50	Medium	Water Soluble
Steel, Low & Medium Carbon Alloy	Below 175	General Purpose	Standard	118°	45-95	Medium to Heavy	Water Soluble
Steel, High Carbon Alloy	175-225	General Purpose	Standard	118°	45-65	Medium	Water Soluble
Stainless Steel, Austenitic	Below 300	Heavy Duty or Nitro®	Split Point	135°	40-60	Medium to Heavy	Water Soluble
Stainless Steel, Precipitation	Over 300	Cobalt	Split Point	135°	20-40	Medium	Cutting Oil

Feeds – Feed rates for drilling are governed by the drill diameter, machinability of materials and depth of hole.
Speeds – The speed of a drill is determined by the rate which the outer periphery of the tool rotates in relation to material being cut. In general, the SFM at which a drill will operate is within a range based upon the workpiece material, its condition, hardness and depth of hole. It is usually advisable to start the drilling process at a slower SFM and then increase to the maximum.
RPM = (SFM x 3.82) divided by TD = Revolutions Per Minute
SFM = RPM x TD x .262 = Surface Feet Per Minute
TD – Tool diameter in inches

Cobalt Drill Bit

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Size Bit Decimal Overall Length Shank Type Item # Availability Price Quantity UOM

31/64

0.4844

5 7/8

Straight

DRIL31/64C

In Stock

$24.22038/EA

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31/64 COBALT JOBBER DRILL BIT

$24.22038/EA

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In Stock

Product Detail

Quantity	Price
Quantity	Price
1	$24.22038/EA

0.2280

3 7/8

Straight

DRIL001C

In Stock

$7.98548/EA

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#1 COBALT JOBBER DRILL BIT

$7.98548/EA

Qty

In Stock

Product Detail

Quantity	Price
Quantity	Price
1	$7.98548/EA
12	$7.98548/EA
48	$6.20447/EA
192	$4.6001/EA

Cobalt Drill Bit

Technical Data

Fractional Sizes

Fractional SizesCobalt Drill Bit

Wire Sizes

Wire SizesCobalt Drill Bit

Letter Sizes

Letter SizesCobalt Drill Bit

Drill Feeds & Speeds

Drill Feeds & Speeds

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31/64 COBALT JOBBER DRILL BIT

#1 COBALT JOBBER DRILL BIT