12 best cobalt drill bits

Product description

Bosch Cobalt M42 metal drill bits are engineered with upgraded M42 alloy, containing 8% cobalt. These hard-core Cobalt bits deliver 10x life vs. Standard bits, are jobber length and withstand high-heat applications. The thick web-helix design delivers fast material removal and increased stability. Bits that are 1/8 in. And larger feature a split point; bits 3/16 in. And larger feature a three-flat shank, for better bit grip. These Cobalt drill bits provide superior performance in stainless steel and can be used to drill cast iron, titanium and other hard or abrasive metals.

• 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

User questions & answers

Question:	Is the entire bit comprised of the M42 8% cobalt alloy or is the high cobalt steel just on the surfaces
Answer:	The entire bit is comprised of the M42 8% cobalt alloy. That is why they should last longer but cost more.
Question:	Are the bits 6” long
Answer:	The CO14B includes (1) 1/16" x 1-7/8", (1) 5/64" x 2", (1) 3/32" x 2-1/4", (1) 7/64" x 2-5/8", (2) 1/8" x 2-3/4", (1) 9/64" x 2-7/8", (1) 5/32" x 3-1/8", (1) 3/16" x 3-1/2", (1) 7/32" x 3-3/4", (1) 1/4" x 4", (1) 5/16" x 4-1/2", (1) 3/8" x 5", (1) 1/2" x 6". If you have further questoins please contact us at a 1-877-BOSCH-99 (1-877-267-2499), M-F 7a-7p CST.
Question:	Length of the bits for each diameter
Answer:	"Hi there, please see the following model with diameter and length size of the bits that comes in CO14B; CO2131 - 1/16"" - 1.875"" CO2132 - 5/64"" - 2.0"" CO2133 - 3/32"" - 2.5"" CO2134 - 7/64"" - 2.625"" CO2135 - 1/8"" - 2.75"" CO2136 - 9/64"" - 2.875"" CO2137 - 5/32"" - 3.125"" CO2139B - 3/16"" - 3.5"" CO4141 - 7/32"" - 3.75"" CO2145 - 1/4"" - 4.5"" CO2147 - 5/16"" - 4.5"" CO2151 - 3/8"" - 5.0"" CO2159 1/2"" - 6.0"" For further assistance, contact us at 1-877-BOSCH99 (1-877-267-2499) from Mon-Fri 7A-7P CST."
Question:	Where are they made
Answer:	The country of origin of the CO21B is China. Robert Bosch Tool Corporation utilizes a global manufacturing strategy, which incorporates a global network of suppliers with our worldwide manufacturing locations in regions such as Asia, Europe, and the United States. Our manufacturing facilities around the globe are all owned and operated by the Bosch Group and maintain the highest quality standards. You can be assured that whatever country your Bosch product was made in, it will be made with the quality you would expect from Bosch. For further assistance, contact us at 1-877-BOSCH99 (1-877-267-2499) from Mon-Fri 7A-7P CST.

Product features

Hard-Core M42 Alloy Cobalt Drill Bits

Bosch Cobalt M42 Metal Drill Bits are engineered with an upgraded M42 alloy, containing 8% cobalt. These hard-core cobalt bits deliver 10X life vs. standard bits and are designed for high heat resistance.

Superior Performance

Designed for durability and with high heat resistance for use in stainless steel, cast iron, titanium, light-gauge metal and aluminum.

No-Skate Tip

Fast, accurate starts reduce bit walking on material surface.

M42 Grade Cobalt

10X longer life than standard Cobalt drill bits.

Thick Web-Helix Design

Fast material removal and increased stability.

Product description

Our Industrial Cobalt accessories now come in ToughCase+ system, the latest addition to our acccessory storage line. The ToughCase+ system are a connectable case system designed to optimize storage space and keep your drill bit sets organized. The patented bit-bar design allows for easy bit removal and the clear lid allows you to see inside at a glance. Industrial cobalt PILOT POINT drill bits are designed for maximum speed and life in stainless steel and other hard metals. DEWALT drill bits sets feature a PILOT POINT tip and split tip design that starts on contact and eliminates bit walking. Commonly used for drilling into stainless steel, drilling into angle iron, i-beams, and other similar metals.

• Connectable accessory storage system to optimize storage space of drill bits for wood, metal or i-beams
• Patented bit-bar design allows easy removal of drill bits and customizable placement
• DEWALT drill bit set comes with clear lid allowing you to easily see contents at glance
• Clip latch for secure closing
• Small Bulk Storage size fits inside the Small and Medium ToughCase+ (sold separately) - Ideal for organizing loose bits
• Maximum speed and life in stainless steel and other hard metals
• PILOT POINT tip starts on contact for clean, accurate holes and reduces lock-up on breakthrough

User questions & answers

Question:	Sorry in advance if this is a dumb question. new diy'er. will these be ok and fit chuck of a dewalt hammer drill? thank you
Answer:	Yes they'll fit any drill chick the only thing they do not fit impact drivers those require a hex shank they will fit but never use the hammer setting with thest bits it'll ruin them
Question:	i have a lowes trailer made of thin angle iron having trouble drilling 1/4 inch holes what type bits do i need
Answer:	These cobalt bits should work fine for that.
Question:	Are these M42 grade
Answer:	This set is M35 grade.
Question:	What % cobalt
Answer:	The bits in this set are 5% Cobalt.

Product description

Ideal for drilling in tough metal, including heavy-duty abrasive alloy metal drilling on hardened steel. Made from industrial grade High-speed steel for increased durability. 8% Cobalt alloy is heat and abrasion-resistant. 135-degree split-point tip starts drilling immediately with less force and eliminates "walking" across the work surface. Metal index case for easy bit access and identification. Includes drill bit sizes 1/16- to 1/2-inch in 1/64-inch increments. IRWIN Tools Cobalt High-Speed Steel Drill Bit, 29-Piece Metal Index Set (3018002).

The Irwin 29-Piece Cobalt M-35 Metal Index Drill Bit Set includes drill bit sizes measuring from 1/16 to 1/2-inch in 1/64 inch increments. The 29 bits are made using heavy duty web construction for strength and durability, and the cobalt steel extends the life of cutting edges. The 135-degree split point tips start drilling on contact and cut with less force. A reduced shank above the 3/8-inch point lets you use larger drill bit in a 3/8-inch chuck, and you can select the right bit using a convenient tap and drill selection chart. The set's rubber overmolded case protects against damage from accidental dropping, and you can remove cartridges to easily carry bits from the case to your worksite.

• 29 Piece
• Cobalt Drill Bit Set
• Sizes 1/16 inch -1/2 inch in 1/64 inch increments, 135 Degree Split Point To Minimize Walk
• 5% Cobalt For Higher Heat & Abrasion Resistance
• Heavy Duty Web Construction For Strength & Durability

User questions & answers

Question:	Are these the Brazil set? I know they make a set from China
Answer:	Made in China with Global materials.
Question:	So is this a cobalt 8% bit (3018002b) or 5% cobalt (3018002)? in product description says 8% but part number says 5%. also is this made in usa
Answer:	Amazon is shipping the 3018002 (5% cobalt) in error and not the 3018002b (8% cobalt) as listed in their product title and description. Wish they would straighten this out.
Question:	Where are these drill bits manufactured? Thanks
Answer:	Glad to read they are made in China. China and Germany make the best drill bits.
Question:	These are NOT 8% Cobalt
Answer:	Amazon is shipping the 3018002 (5% cobalt) in error and not the 3018002b (8% cobalt) as listed in their product title and description. Wish they would straighten this out.

• Cobalt high speed steel along with the titanium coating ensures extreme durability, will stay new and shiny for years to come.
• Different sized shanks ensure compatibility with 1/4, 3/8 and 1/2 in. chuck sizes.
• Non-walking drill tip provides fast and smooth drills on steel sheets, aluminum sheets, wood board, plastic board etc. (the board must be smaller in thickness than the height of step drill bits).
• Please mark the spot that you are to drill for easier drilling and improved drill bits life.
• All the bits come in a well-organized case for easy transport and storage.

User questions & answers

Question:	How good is the quality
Answer:	This is a set of 5 drill bits. You can use either 3/8 or 1/2 drill with the drill bits included.
Question:	Is this for a 3/8 drill or
Answer:	You don't "need" any of these bits. Both, my...another family member and I purchased these as the touting of cobalt, titanium, and High Speed Steel bits made us both believe they were a steal of a steel deal. Boy we couldn't have been more wrong! Destroyed 1st use at slow speed off the speed chart and using tapping fluid to lubricate. These are absolute garbage. AGAIN THESE ARE ABSOLUTE GARBAGE BITS. I've got a free pocket knife from a gas station that drills better. Shavings from the first time we used these bits were put in the MassSpec at his showed NO cobalt at all present. For those that don't know a mass spectrometer gives you a breakdown of the molecules and elements present in a sample. Upon my complaining to the seller, I was told well.... "They're only cobalt colored and aren't intended for use on steel or hard metal alloys." You buy a cobalt %containing bits to handle the higher frictional heats encounters when cutting/drilling tougher steel alloys, stainless, or even just wanting your High Speed Steel bits to last longer. It's so your bit doesn't take damage and be destroyed or worse yet damage the piece you're drilling (especially when you're using tapping fluid too to lubricate the cutting edges reducing that friction and subsequent damaging heat) and M42 is the highest grade of cobalt bits I have & that I know of / have used. You buy titanium bits from M7 (high molybdenum for toughness) to M35 (HSS with a 5% titanium component) or the king of titanium bits and heat dissipation (HSS with 8% titanium) so your bits won't be damaged to the point they're unable to be used again. These high end bits you pay for ones made right. There are proper recipies the boundaries mix up molten of all the components from the iron and nickel of base steel, to adding molybdenum for toughness, cobalt for thermal resilience, titanium coatings to reduce friction, and many many more components in a bakery for steel. These bits are beyond poorly made and are NOT good moreless decent bits. So I'll reiterate fro my own and others experience, THESE ARE JUNK AND YOU DONT "NEED" THEM.....well unless you need to drill holes in pure Gallium at ambient temperatures above 30°C. And just a FYI I have 1/8" M42 aircraft legnth bits that'll drill through a 10" hardened steel block and a 1.0" M42 bit that could just about drill aluminum foil without tearing it. Size has nothing to do with quality. Small bits for small sheets and big bits for big sheets is a cop out answer to make the customer think they're the problem in how they're using the bits. The bits are crap and the Seller sends different answers to different people. They're garbage bits from cheap garbage metal (I hesitate to even call them true steel) see less
Question:	Are these bits titanium or cobalt? The product description shows both titanium & cobalt
Answer:	You don't "need" any of these bits. Both, my...another family member and I purchased these as the touting of cobalt, titanium, and High Speed Steel bits made us both believe they were a steal of a steel deal. Boy we couldn't have been more wrong! These are absolute garbage. AGAIN THESE ARE ABSOLUTE GARBAGE BITS. I've got a free pocket knife from a gas station that drills better. Shavings from the first time we used these bits were put in the MassSpec at his showed NO cobalt at all present. For those that don't know a mass spectrometer gives you a breakdown of the molecules and elements present in a sample. Upon my complaining to the seller, I was told well.... "They're only cobalt colored and aren't intended for use on steel or hard metal alloys." You buy a cobalt %containing bits to handle the higher frictional heats encounters when cutting/drilling tougher steel alloys, stainless, or even just wanting your High Speed Steel bits to last longer. It's so your bit doesn't take damage and be destroyed or worse yet damage the piece you're drilling (especially when you're using tapping fluid too to lubricate the cutting edges reducing that friction and subsequent damaging heat) and M42 is the highest grade of cobalt bits I have & that I know of / have used. You buy titanium bits from M7 (high molybdenum for toughness) to M35 (HSS with a 5% titanium component) or the king of titanium bits and heat dissipation (HSS with 8% titanium) so your bits won't be damaged to the point they're unable to be used again. These high end bits you pay for ones made right. There are proper recipies the boundaries mix up molten of all the components from the iron and nickel of base steel, to adding molybdenum for toughness, cobalt for thermal resilience, titanium coatings to reduce friction, and many many more components in a bakery for steel. These bits are beyond poorly made and are NOT good moreless decent bits. So I'll reiterate fro my own and others experience, THESE ARE JUNK AND YOU DONT "NEED" THEM.....well unless you need to drill holes in pure Gallium at ambient temperatures above 30°C. And just a FYI I have 1/8" M42 aircraft legnth bits that'll drill through a 10" hardened steel block and a 1.0" M42 bit that could just about drill aluminum foil without tearing it. Size has nothing to do with quality. Small bits for small sheets and big bits for big sheets is a cop out answer to make the customer think they're the problem in how they're using the bits. The bits are crap and the Seller sends different answers to different people. They're garbage bits from cheap garbage metal (I hesitate to even call them true steel)
Question:	Noob question, but why do I need five of these bits? It seems like you could get all the increments with one or two
Answer:	It will definitely cut aluminum...its I deal for porting a cylinder head...

Product features

Advantages of HSS Step Drill Bits

• HIGH QUALITY MATERIAL: 5% Cobalt High Speed Steel M35 provide extended tool life compared to ordinary drill bits. Durable and strong
• TWIST DESIGN & PERFORMANCE: PRECISE 135°SPLIT POINT, gold oxide finish and round straight shanks. Prevent walking, clear chips and particles faster.Produced by precision fully ground which ensures chips move smoothly.
• PROFESSIONAL & WIDELY USE: M35 Cobalt HSS is more suitable for hardened material. Particularly successful in cutting through hard metals such as stainless steel, cast iron, high temperature alloy, titanium alloy, hard plastics and woods, and also can be used for softer materials.
• SIZE INCLUDED: 15pcs jobber length drill bit set with plastic storage case including sizes:1/16" 2pc,5/64" 1pc ,3/32" 2pc,7/64" 1pc,1/8" 2pc ,9/64" 1pc, 5/32" 1pc, 3/16" 1pc, 7/32" 1pc, 1/4" 1pc, 5/16" 1pc, 3/8" 1pc.
• 100% SATISFACTION GUARANTEE: If you are not 100% satisfied with your purchase for any reason whatsoever simply please feel free to contact us.

User questions & answers

Question:	if these are not really meant for, let's say hanging blinds on a steel/metal door, what should I use
Answer:	You can, but you would need cutting oil!
Question:	What is the warranty on this Comoware cobalt 15pc drillbit set
Answer:	“Satisfaction guaranteed” or contact company, the company most likely will give you the run around
Question:	Does it work for stripped hex screws
Answer:	Have not tried on Hex heads, but should work fine. Should not have to use the drilling action, just the extraction.
Question:	How well do these cut through stainless steel. More specifically 3/8 inch thick stainless steel support beams
Answer:	Use a little lubricant and it'll drill like butter. I used these to drill a bunch of holes in 1/4 stainless with no problem whatsoever. Great bits

Product features

COMOWARE Cobalt Twist Drill Bit Set-15 Pcs

Specifications:

Material: HSS M35 Cobalt 5%

Angle Point: 135 Degree

Flute Type: Spiral

Shank Type: Straight Shank

Size Includes:

1/16" 2pc,5/64" 1pc ,3/32" 2pc,7/64" 1pc,1/8" 2pc ,9/64" 1pc, 5/32" 1pc, 3/16" 1pc, 7/32" 1pc, 1/4" 1pc, 5/16" 1pc, 3/8" 1pc.

M35 Cobalt HSS:

It is more suitable for hardened material,such as stainless steel, cast iron, high temperature alloy, titanium alloy, hard plastics and woods, and also can be used for softer materials.

Product description

Bosch cobalt drill bits are specially designed for drilling in hard steel. Thick web helix delivers fast material removal combined with increased durability for maximum efficiency and performance. Each bit is manufactured to exacting specifications and features a split point that starts on contact with no walking or skating, eliminating the need for a center punch.

From the Manufacturer

The Bosch line of metal drill bits offers a solution for every professional application. Each bit is manufactured to exacting specifications and features a 135 Degree split point that starts on contact with no walking or skating, eliminating the need for a center punch.

• Withstands high-temperature applications for extended periods of time (up to 1,100 degreeF)
• Rigid, thick web design adds stability to bit in tough applications
• Surface hardened to penetrate tough abrasive materials
• Available in jobber length, full shank
• Best used for drilling into light-gauge metal, high-carbon steel, aluminum and ally steel, cast iron, stainless steel and titanium

User questions & answers

Question:	Are these strong enough to drill through 1/2in steel
Answer:	Yes, the Bosch CO2140 cobalt drill bits are specially designed for drilling in hard steel and have a flute length of 2.44". For further assistance, contact us at 1-877-BOSCH99 (1-877-267-2499) from Mon-Fri 7A-7P CST.
Question:	How long are these bits
Answer:	They are about 2 inches long from tip to tail.
Question:	Will bit drill glass at low rpms
Answer:	No
Question:	How long are these bits
Answer:	1 and 7/8 inches

Product features

Withstands high temperature

Withstands high-temperature applications for extended periods of time (up to 1,100°F)

Long life

4X the lifespan of standard metal drill bits

Tough applications

Surface hardened to penetrate tough abrasive materials

Various assortment

Available in jobber length, full shank

Black Oxide for general purpose drilling

(Also available at Impact Tough range)

Titanium for heavy duty repetitive drilling

(Also available at Impact Tough range)

Cobalt for heavy duty drilling in extremely hard or abrasive materials

Product description

• Set of 29 jobber length drill bits includes inch sizes 1/16" to 1/2" in 1/64" increments
• Cobalt steel provides extended tool life compared to high-speed steel drill bits when drilling hard materials
• Gold oxide finish lubricates the drill bit and provides wear resistance
• Self-centering 135-degree split point penetrates hard material without a pilot hole and produces small chips to reduce clogging
• Meets ANSI specifications

User questions & answers

Question:	What is the overall length of the longest bit
Answer:	The 1/2" bit I got was 6 1/16" long. 3/8" was 5 1/16" long, 1/4" was 4 1/16" long, 1/8" was 2 3/4" long. 1/16" was 1 3/4" long.
Question:	Where are these bits made
Answer:	I peeled off the applied foil stickers and took the plastic case apart, but could not find any clue as to the manufacturing country. However, they have been completely satisfactory in use.
Question:	Are these bits made in the USA
Answer:	For all who are asking , Drill America is a USA manufacturer. These bits are AMERICAN made.
Question:	Are these made in the USA??? or China
Answer:	No indication anywhere on the case. I looked at every bit and nearly all only had HSS CO and the bit size. The 31/64 has USA.

Product features

All The Bits You Need

29 Piece Sets includes fractional sizes from 1/16" to 1/2" by 1/64" increments.

Hang for Quick Access

When all hands are on deck, hang the drill index on your belt whether you're in the shop or field.

Easy to Handle Plastic Case

Unique round drill index combines form and function into one beautifully designed, easy to carry drill set.

Fits Anywhere You Need It

Effortlessly grip the set in one hand as you would a travel coffee mug or leave it in the cup holder of your truck while on the way to a job.

135 Degree Split Point Tip

Drill America Cobalt Drill Bits have a 135 degree split point tip for self-centering and reducing thrust. Compared to a conventional 118 degree tip, these drills wont go "walking" on you.

Product description

M35 COBALT HSS DRILL BIT SET SIZE INCLUDED:

29pcs Drill Bit Set：1/16" 5/64" 3/32" 7/64" 1/8" 9/64" 5/32" 11/64" 3/16" 13/64" 7/32" 15/64" 1/4"

17/64 9/32" 19/64" 5/16" 21/64" 11/32" 23/64" 3/8" 25/64" 13/32" 27/64" 7/16" 29/64" 15/32" 31/64" 1/2"



PRODUCT FEATURE:

M35 COBALT HSS Material

135 Degree Angle Point

Straight Round Shank



APPLICATION:

M35 cobalt hss drill bit set are especially good at cutting hard metals such as stainless steel,

cast iron, superalloy, titanium alloy, hard plastic and wood. It can also be used in soft materials.



PRECAUTIONS:

Make sure to put on masks and gloves before drilling.

Keep cool or discontinuous use will largely prolong drill life.

Keep the drill bits vertical to the object when drilling

Be sure to make both bit and work piece stable. Tilted bit is prone to break



Please contact us at the first time if you have any question about our product , we are happy to help you.☺

• SIZE INCLUDED: Drill bit set 29pcs include 1/16", 5/64", 3/32", 7/64", 1/8", 9/64", 5/32", 11/64", 3/16", 13/64", 7/32", 15/64", 1/4", 17/64", 9/32", 19/64", 5/16", 21/64", 11/32", 23/64", 3/8", 25/64", 13/32", 27/64", 7/16", 29/64", 15/32", 31/64", 1/2",which can meet more requirements
• HSS DRILL BIT SET :HSS cobalt drill bit set for hardened steel has excellent cutting performance, drill bit set 29pcs can be used for a long time, The cutting edge is hardened and honed for sharpness, with superior sharpness, accurate cutting without shaking
• M35 COBALT CHARACTERISTICS : M35 cobalt drills bit set is effective in drilling tough, high tensile strength materials，drill bit is especially good at cutting hard metals such as stainless steel, cast iron, superalloy, titanium alloy, hard plastic and wood. It can also be used in soft materials
• 135° SPLIT POINT: Cobalt drill bit set for hardened steel is 135° split point tip and torsional design to improve cutting speed, self-centering, prevent walking, and faster chip and particle removal
• ORGANIZED HOLDER: Cobalt drill bit set includes a drill stand with size index for easy storage and organization. drill bit set is suitable for most brands on the market.reliable quality and considerate service. If you have any questions, please feel free to contact us, we will do our best to serve you

User questions & answers

Question:	Are they really''cobalt
Answer:	Yes. The drill bit set is cobalt drill bit set.
Question:	Neither the box and the case say they are cobalt
Answer:	Yes, they are cobalt.
Question:	What percentage is the Cobalt
Answer:	Dear friend, the drill bit set contains 5% cobalt。
Question:	Where are they made
Answer:	China andcome with a plastic box that broke right away

Product description

Product Advantages:



3 Steps desigh tip starts drilling immediately with less force and eliminates "walking" across the work surface.

Holds up better than generic high-speed steel,Cobalt gives high-speed steel more heat and wear resistance.

This drill bits set is made of Premium Cobalt (80,000 dollars per ton).

The M42 metric cobalt drill bits can cut through Stainless steel and Hard metal,Hard wood, although they can be used for softer materials such as Aluminum,Plastic.



Some Important Tips about drilling stainless steel and hard metal:

    Controling the drill speed from 200 to 1000 RPM would make it easier for you to drill holes on stainless steel.

________________________________

                Stainless Steel                  

    ____________________________

      Drill diameter               RPM        

    ____________________________

      ≤5mm                       1000~700

    ____________________________

      5-10mm                     700~350

    ____________________________

      10-15mm                   350~200

________________________________



    Add stainless steel tapping oil or engine oil to prevent the stainless steel from overheating and forming a very hard oxide layer.It also works adding some vinegar,soy sauce or water if you don't have engine oil.

• Premium M42 8% Cobalt Steel ,68-70 HRC (Rockwell Hardness Scale) ,Usually Give the Best Heat,Wear and Chip Resistance and Long Tool Life.
• 3 Steps Desigh for Cutting through Stainless Steel,Hard Metals,Aluminum,Plastic.
• This Cobalt Drill Bit is Typically Capable of Running Three to Five Times Faster.Despite the Higher Price,the Cost Per Hole When Using Cobalt Drill Bit Will be the Lowest,Since It Can Produce So Many More Holes.
• The Sufficiently Sharp Bit Edge Can Cut the Metal Material into Long Strips of Iron Chips rather than Slowly Grinding Throng the Material with a Blunt Drill Bit.
• 19Pcs 135 Degree Split Point Drill Bits Includes :1mm(length:3.4cm)\1.5mm\2mm\2.5mm\3mm\3.5mm\4mm\4.5mm\5mm(length:8.5cm)\5.5mm\6mm(length:9cm)\6.5mm\7mm\7.5mm\8mm(length:11.5cm)\8.5mm\9mm\9.5mm\10mm(length:13cm) [DIA 0.5mm Increments] .

User questions & answers

Question:	Does the larger bits have reduced shanks
Answer:	no they pretty much correspond to the size of the bit
Question:	Can these drill through a car's trunk without any issues
Answer:	I don't know which part of the trunk you're talking about. I used them to drill through solid 10mm round rod. They worked well.
Question:	What is the length of these bits
Answer:	They are average lengths. The 1mm is 3.4cm and length increase proportionally to the 10mm which is 5.4cm.
Question:	Do they work on wood
Answer:	They would work on wood but are a little "overkill". These are designed for hard metals.

Product description

Bosch cobalt drill bits are specially designed for drilling in hard steel. Thick web helix delivers fast material removal combined with increased durability for maximum efficiency and performance. Each bit is manufactured to exacting specifications and features a split point that starts on contact with no walking or skating, eliminating the need for a center punch.

From the Manufacturer

Bosch cobalt drill bits offer the best heat resistance and rigid thick web design for drilling in extremely hard and abrasive materials such as treated stainless steel (precipitation-hardened), cast iron and titanium.

• Withstands high-temperature applications for extended periods of time (up to 1,100 degreeF)
• Rigid, thick web design adds stability to bit in tough applications
• Surface hardened to penetrate tough abrasive materials, Cuts through light gauge metal, high carbon steel, aluminum and alloy steel, cast iron and stainless steel
• Available in jobber length, full shank, Drill Point Angle is 135 degrees, Surface Coating is uncoated (bright finish), Bit type is Twist
• Best used for drilling into light-gauge metal, high-carbon steel, aluminum and ally steel, cast iron, stainless steel and titanium

User questions & answers

Question:	do you need water etc
Answer:	Cobalt bits are cobalt/steel alloy, generally 5% to 8% cobalt. This makes them harder and more heat resistant. Water or oil serves two purposes. These fluids do help cool the bit, but they also help with chip removal from the hole. I would use one or the other most of the time, especially if you are drilling harder material like stainless steel. Another helpful technique is to use progressively larger bits, for example, 1/16 or 3/32 to start, 1/8, 3/16, and finally 1/4 in your instance.
Question:	What is the drill angle
Answer:	Thank you for your question. The CO2413 is a straight bit, it does not have an angle. For further assistance, contact us at 1-877-BOSCH99 (1-877-267-2499) from M-F 7A-7P CST.
Question:	Do these work with a hole saw kit
Answer:	The CO2143 Cobalt Drill Bit is designed to drill through metals alone. Hole Saws can be used with a mandrel. For further assistance, contact us at 1-877-BOSCH99 (1-877-267-2499) from Mon-Fri 7A-7P CST.
Question:	how long is the drill bit
Answer:	Thank you for your question. The CO2143 is 4" overall. If you have further questions please feel free to contact our Bosch Customer Service Representatives at 1-877-BOSCH-99 (1-877-267-2499).

Product features

Withstands high temperature

Withstands high-temperature applications for extended periods of time (up to 1,100°F)

Long life

4X the lifespan of standard metal drill bits

Tough applications

Surface hardened to penetrate tough abrasive materials

Various assortment

Available in jobber length, full shank

Black Oxide for general purpose drilling

(Also available at Impact Tough range)

Titanium for heavy duty repetitive drilling

(Also available at Impact Tough range)

Cobalt for heavy duty drilling in extremely hard or abrasive materials

• M35 COBALT STEEL - Manufactured from M35 cobalt steel, with molybdenum and cobalt added to creates a hardened alloy, measuring Rockwell hardness up to 67, for much faster cutting and extra longer life span, with up to twelve times when compared with an average HSS drill bit.
• Point Angle - The 3mm bits are 135° split pointed, which is self-centering and will penetrate quickly with less pressure. Will not "walk" or "wander". The other small ones are 118°.
• FOR STAINLESS STEEL - Particularly successful in cutting through hard metals such as stainless steel and cast iron, although they can be used for softer materials, too. Not for hardened steel / high carbon steel. Try to adjust the RPM when it fails to penetrate.
• 50PC SET - The set includes 50pcs of metric M35 cobalt steel twist drill bits: 1mm, 1.5mm, 2mm, 2.5mm, 3mm. 10 each metric drills in popular hobbyist sizes at low price. Manufactured to German DIN338 standard.
• Packed in a plastic bag. These bits are quite small. Please refer to the picture including a size chart.

User questions & answers

Question:	I want to drill 9 to 12 holes through large, stainless steel hinges (3mm thick).Could I do the job with these drills
Answer:	Quality of hinge is the variable here. I would buy a single cheap coated drill bit first. If you can drill one hole with the cheap bit, then you should be able to drill 9-12 in the same material with this set. As always use cutting oil and make sure your press is set to proper speed.
Question:	is the drill bits pure cobalt
Answer:	Thanks for your question. Cobalt drill bits are not made of pure cobalt, but rather a steel alloy with 5 to 8 percent cobalt. The 5-percent alloy is known as M35 grade, and the 8-percent alloy is M42. These bits are made of M35 grade cobalt steel, with 5% cobalt added.
Question:	Are most of these reviews fake? 50 real cobalt bits for $15 is impossible
Answer:	We swear every review in our store is real. Our living relies on this account. We'll never risk making fake reviews, or it might be closed by Amazon. Pay attention to the size. These bits are small. The 1mm is like a needle. You guys paid extra too much for those famous brands before. Selling it at $15 is profitable for us.
Question:	Description says not good for hardened steel -- what kind of bits are good for hardened steel? i keep buying, bits keep failing
Answer:	Thanks for your question. Carbide bits can be used to drill hardened steel.

Product features

Hymnorq M35 5% Cobalt Steel Twist Drill Bits Set

• M35 Grade Cobalt Steel - Cobalt drill bits are not made of pure cobalt, but rather a steel alloy with certain percent cobalt. The 5-percent alloy is known as M35 grade. The cobalt increases the strength of the steel and makes it more heat-resistant.
• Lowest Cost Per Hole Drilled - Cobalt bits are more expensive than ordinary HSS drill bits. But if you regularly drill metals, they are a good investment since they tend to last longer. With an extended life, you can lower cost per hole drilled.

Selected M35 Cobalt Steel Raw Material

5% cobalt added for

• Higher heat resistance
• Faster speeds
• Higher feed rates

High Level of Craftsmanship

• Advanced machines
• Experienced workers
• Precision grinding technique
• Smoother hardened surface

Strict Inspection

• Every piece of bit is inpected by precision instrument before being packed
• Quality never comprised

Be Vertical

• Keep the drill bit vertical with the stuff's surface to be drilled.
• Tilted bit is prone to break during drilling.
• Be sure to make both the bit and the workpiece stable.

Do It Slow

• Drilling metal requires low RPM. Please use a device of which the drilling speed can be adjusted.
• Be careful when you use an electric drill. The RPM could be set too high.
• The thicker the bit, the slower speed should be.
• If you're not sure, please start from the lowest RPM and pressure.

Stay Cool

• Friction between bit and metal will accumulate an amount of heat.
• It's necessary to use cooling liquid during drilling to keep the bit cool. Otherwise, the bit may fry(melt) or only last a short time.
• It's both ok to use lubricant oil and to pour water.

Right Drilling Device

• It's highly recommended that you use a drill press to drill thick metals. It's stable, powerful and (RPM) adjustable.
• If a drill press isn't available, electric drill or charging drill will do the job, too. However, it's more likely you'll meet problems unless you're really experienced.

Product description

EFFICERE 8-Piece Silver and Deming Drill Bit Set is an essential tool and perfect choice for drilling large holes over 1/2” diameter in wood, plastic, aluminum, copper, stainless steel, sheet metals and many other types of materials. Constructed from premium cobalt high speed steel for dependable strength, these drills bits are built to last. Featuring 135 degree split point at tip, they start cutting with self centering for faster speed and prevent walking during drilling. A superior gold titanium and black nitride dual coating finish is applied to each drill that holds up lubricant better for smoother drilling and is 80% more durable and corrosion resistant than regular black enamel finish. All the drills have a universal 1/2 inch reduced shank with tri-flat end and securely lock onto any 3-jaw chuck from all brands of power tools. Set includes 8 pieces of 6” length silver & deming drill bits in a handy aluminum storage case for easy carrying and organization: 9/16, 5/8, 11/16, 3/4, 13/16, 7/8, 15/16, and 1”.

• Premium cobalt high speed steel construction for proven capability and durability to drill holes in wood, plastic, aluminum, copper, stainless, sheet metals and many other types of materials
• Superior gold titanium and black nitride dual coating finish holds up lubricant better for smoother drilling, and is 80% more durable and corrosion resistant than regular black enamel finish
• 135° Split point design at tip increases cutting speed with self-centering feature and prevents drill walking or wobbling
• 1/2 Inch reduced shank with tri-flatted end locks onto 3-jaw power tools chuck more securely and eliminates slips
• Set includes 8 pieces 6” long silver & deming drill bits in a heavy duty aluminum storage case for easy carrying and organization: 9/16”, 5/8”, 11/16”, 3/4”, 13/16”, 7/8”, 15/16”, 1”

User questions & answers

Question:	will this cut 1/4 steel
Answer:	Yes it will cut 1/4" steel.
Question:	Can it drill through Brick
Answer:	My answer would be no. These bits are primarily for drilling metal. They will drill wood, plastic and like products but they are NOT designed for drilling masonry which would include concrete, concrete blocks, and brick.
Question:	Will these bits work on acrylic
Answer:	haven't tried this set ,,,,how ever Silver and Deming are 100% are good ol USA great bilt tools … try u tube to find the best way to drill acrylic,,,,,,,, I ve had good results in running high speed ,,,,,how ever ive come up with different ideas on u tubes web site,,,( try on a scrap piece of same thickness ….Good work ~~~~~~~~~~ recall ididnt say good luck ,,,if you plan research ask some one and try it out on scrap luck is not a factor YOU are be a craftsman hope this helps ,,,,,,Frank in Clover sc
Question:	Will these drill hard stainless steel
Answer:	Probably not. The bit set I received did not drill aluminum, until I honed the cutting edge with a very fine grit diamond file, because the cutting edge had small burrs (incomplete final machining). The bits are labeled HSS (high speed steel), which is ordinarily good for cutting most stainless steels, when the bit cutting edges are honed razor sharp without residual burrs. So this inexpensive bit set is good for the machinist who can finish the honing of the cutting edges with a diamond file or a diamond drill bit sharpener.