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6 VIDEOS

BOSCH Cobalt Drill BitsBOSCH (S-B Powertools)

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BOSCH CO2151B 1-Piece 3/8 in. x 5 in. Cobalt M42 Metal Drill Bit with Three-Flat Shank for Drilling Applications in Stainless Steel, Cast Iron, Titanium, Light-Gauge Metal, Aluminum

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Material	Cobalt
Cutting Diameter	0.38 Inches
Finish Type	Titanium
Shank Type	3-Flat
Cutting Angle String	135 Degrees

About this item

Cobalt M42 drill bit – provides upgraded M42 Cobalt jobber-length bits designed for durability, high heat resistance and Hardened surface for stainless steel, cast iron, titanium, light-gauge metal and aluminum
Enhanced M42 alloy material – contains 8% Cobalt alloy that delivers 10x life vs. Standard bits
High-heat resistant bits – withstand high-temperature applications for extended periods of time
Thick web-helix design – provides additional stability in tough applications
Surface-hardened tip – penetrates tough abrasive materials

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This item: BOSCH CO2151B 1-Piece 3/8 in. x 5 in. Cobalt M42 Metal Drill Bit with Three-Flat Shank for Drilling Applications in Stainless Steel, Cast Iron, Titanium, Light-Gauge Metal, Aluminum

$7.99

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DEWALT DWA1207 7/64" Pilot Point Industrial Cobalt Alloy Steel Drill Bit

$4.53

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BOSCH CO2136 1-Piece 9/64 in. x 2-7/8 in. Cobalt Metal Drill Bit for Drilling Applications in Light-Gauge Metal, High-Carbon Steel, Aluminum and Ally Steel, Cast Iron, Stainless Steel, Titanium

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Josh M
100% worth the cost
Reviewed in the United States on November 23, 2024
Size: 9/64 x 2-7/8 Inch (Pack of 1)Verified Purchase
Anything bosch makes is good, but i feel like they have it down pat when it comes to stuff like twist drills and bits.

The M42 cobalt keeps the drill from getting too hot and also acts as a "lubricant", both contributing to keeping a sharp cutting edge, giving it quality and ease of use.

These factors reduce the need for either resharpening, or worst, replacing the drill. The cost of cobalt bits are what scares people away, but if you're gonna be using it more than 2 or 3 times, its worth the upgrade from black oxide or a coated bit, thus giving it great value for money.

The "M42" is a reference for the amount of cobalt used in the "material makeup" of the bit, with 8% cobalt being used in M42, and 5% cobalt in M35. Both are great options, but i recommend getting an M42 version when possible.

The use of cobalt doesnt change the size or shape of the drill, although some will have different flute counts and designs, some tips have a "no pilot hole" start and some will have different degrees of an angle at the head to help with different types of material. Overall, storage capacity will not change unless you opt for different lengths, such as mechanics and aviation length.

To sum this up, this is a great drill that should last a long time if used correctly. Bosch is very prevalent in my drill cabinet, so dont be afraid to spend a little extra and get the good one!

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8 people found this helpful

Helpful

thetraveler
great for drilling metal
Reviewed in the United States on October 14, 2024
Size: 14 pc. Drill Bit SetVerified Purchase
Got this kit for blacksmith shop.
I have used it in a hand drill and a drill press.
I drilled multiple holes in succession in 1/4 , 3/8, and 1/2 inch soft steel.
using the 1/4 and 3/8 inch bits.
Worked well. The bit are durable. None have broken and they remain sharp through multiple jobs.

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2 people found this helpful

Helpful

Mobius
Amazing Bits!
Reviewed in the United States on June 1, 2024
Size: 14 pc. Drill Bit SetVerified Purchase
I never knew the magic of cobalt drill bits until I needed to drill some mounting holes on a steel bench grinder stand. The top of the stand was 3/8 in steel plate and it probably took 20 minutes to get through it with a standard bit.

I did some research and ordered these bits. I don't need 50 different sizes because I'm not drilling metal frequently. This Bosch set seemed to be one of the few affordable sets that included the 1/2-in size. Plus... All of the bits above 3/16 I have a three-sided flat grind for better chuck lock up.

Used the 1/4 in bit for a pilot and then the half inch bit to drill the remaining three holes. Less than 1 minute per hole, including the pilot, using a bit of cutting oil. It really is like magic.

I'll be testing these to drill out a broken bolt in my mower deck next. I will update this review if I experience any durability issues.

UPDATE: That broken spindle bolt in my mower deck must be special. Using low speed, a lot of pressure, and cutting oil I made it about a quarter inch into the bolt before dulling the bit. Switched to another bit and made it a bit further before killing that one too. Even with a decent hole drilled in the bolt, my extractors won't grab the hard metal. I'm not going to deduct a star since I didn't expect these bits to be invincible but hope this helps someone determine if these will work for your use case.

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8 people found this helpful

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delump
top of the line
Reviewed in the United States on February 12, 2025
Size: 14 pc. Drill Bit SetVerified Purchase
Several uses so far. Bolts, screws, drywall, plastics, it created clean holes without any problems. Recommended as your go-to bits.

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Helpful

E.R.
Decent quality drill bit set.
Reviewed in the United States on January 7, 2025
Size: 21 pc. Drill Bit SetVerified Purchase
I find this to be a decent quality drill that set. The application is for Hobby use. I would not say these are industrial bits, but certainly better than the average, for Hobby use or for the homeowner.

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Helpful

Damo
Bosch m42 Cobalt bits work great for at home use.
Reviewed in the United States on January 12, 2025
Size: 21 pc. Drill Bit SetVerified Purchase
So far so good beats my regular metal DeWalt bits hands down. Seems like a good value and good quality with a nice storage case. They are made in China I was not sure where they were made when purchasing.

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2 people found this helpful

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FRAN
Excelente
Reviewed in the United States on January 11, 2025
Size: 14 pc. Drill Bit SetVerified Purchase
It's Bosch so the quality is included. It works very well.

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J.Cardona
Awesome!
Reviewed in the United States on January 27, 2025
Size: 14 pc. Drill Bit SetVerified Purchase
Tried some cheap Cobalt IRWIN bits and they just couldn't do the job, THESE bits by Bosch are AWESOME, it took me literally just 35 minutes to remove and replace a lug nut bolt with the help of these babies, they went through the bolt like it was nothing. Totally recommended!!!

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Etienne Gallant
High quality drill bit
Reviewed in Canada on January 2, 2025
Size: 3/32 x 2-1/4 Inch (Pack of 1)Verified Purchase
I was able to drill 4 aluminum rivets from a snowblower starter rope assembly easily. This drill bit was strong enough to drill these 4 rivets in no time. I like to use some « gel-tap » to lube the tip of the drill bit and prolong the life of it. It also helps retrieve metal shavings from falling everywhere.

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Jared
Saved my bacon
Reviewed in Canada on November 11, 2024
Size: 21 pc. Drill Bit SetVerified Purchase
snapped a transmission pan bolt on my 2017 Ram 1500, I started with a HSS drill bit, but it wouldnt cut into the bolt, seems 85,000 mi hardened the steel. Once these drill bits came in, I was able to easily drill out the broken bolt and retap the threads. Worth every penny

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Heikki Isomaa
Excellent drill set.
Reviewed in Canada on October 29, 2024
Size: 14 pc. Drill Bit SetVerified Purchase
Tried drilling out broken exhaust studs with run of the mill drills. They were ineffective and found these excellent hard drills on Amazon. These hardened drills did the job quickly and are still sharp.

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Gordon Wedman
Did the job
Reviewed in Canada on September 24, 2024
Verified Purchase
These worked great to drill the hard metal A pillar in my LR3 that other people reported having trouble drilling. Didn't even need the second one.

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L
Love that I can buy a single bit.
Reviewed in Canada on September 23, 2024
Size: 9/64 x 2-7/8 Inch (Pack of 1)Verified Purchase
High quantity drill bit to supplement my already complte set. It is longer than the ones in a set. Great when you need to drill a deeper hole.

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BOSCH CO2151B 1-Piece 3/8 in. x 5 in. Cobalt M42 Metal Drill Bit with Three-Flat Shank for Drilling Applications in Stainless Steel, Cast Iron, Titanium, Light-Gauge Metal, Aluminum

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Great NO irritating clam shell outer plastic case

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5.0 out of 5 stars High quality drill bit

5.0 out of 5 stars Saved my bacon

5.0 out of 5 stars Excellent drill set.

5.0 out of 5 stars Did the job

5.0 out of 5 stars Love that I can buy a single bit.

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High quality drill bit

Saved my bacon

Excellent drill set.

Did the job

Love that I can buy a single bit.