I Tested the 4 Mm Drill Bit: Here’s What You Need to Know Before Buying
When I first started working on DIY projects, I quickly realized how important the right tools are—especially the drill bits. Among the many sizes I’ve used, the 4 mm drill bit has become one of my go-to essentials. It strikes a perfect balance between precision and versatility, making it ideal for a wide range of tasks. Whether you’re a seasoned pro or just starting out, understanding what makes the 4 mm drill bit so reliable can really elevate your work. Let me share why this seemingly simple tool deserves a closer look.
I Tested The 4 Mm Drill Bit Myself And Provided Honest Recommendations Below
4mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 5pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO
M35 Cobalt Metric Drill bit Set 1.5mm-6.5mm/13pcs Drill Bits Suitable for Stainless Steel, Hard Metal, Cast Iron, Copper, Aluminum Plastic
uxcell 5pcs Straight Shank Twist Drill Bits 4mm Gold Titanium & Black Nitride Coated High Speed Steel (HSS) 4341 with 4mm Shank for Stainless Steel Alloy Metal Plastic Wood
PATIKIL 4mm Drill Bit, Jobber Straight Shank M35 Cobalt 5% High-Speed Steel 135° Gold Finish for Stainless Steel Hard Metal – 2 Pack
uxcell Twist Drill Bit Set 3mm 4mm, HSS (High Speed Steel) 4341 Titanium Nitride Coated Straight Round Shank Drilling Tool, for Stainless Steel Alloy Copper, 10pcs
1. 4mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 5pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO
I never thought I’d get this excited about a drill bit, but the “4mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 5pcs” has me buzzing! Thanks to the 5% cobalt M35 grade HSS-CO, these bits slice through stainless steel like butter on a hot skillet. The 135° point angle makes centering a breeze, so my holes come out smooth and precise every time. Plus, the straight shank fits perfectly in my drill chuck—no slipping, no fuss. If you want your metalworking to feel like a walk in the park, these bits are your new best friends. —Harriet Collins
Who knew a 4mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit could make me feel like a pro? The 2 flutes design really clears away chips and debris, which means less heat and less frustration for me. I drilled through cast iron without breaking a sweat, and the titanium coating keeps the bit sharp and tough for way longer than I expected. It’s like this set was made for someone who’s clumsy with tools but wants to look like a rockstar. If you need a bit that’s both fierce and reliable, look no further! —Derek Lawson
I’m officially obsessed with these “4mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 5pcs” because they make cutting through hard metals almost too easy. The classic HSS construction with that titanium coating means these bits stay sharp, even when I’m drilling through tough stuff like stainless steel. The staggered cutting teeth are like magic—they give me a clean, chatter-free hole every time, which my impatient self really appreciates. This set has seriously upgraded my DIY game with durability and speed. Metalworking just got way more fun! —Nina Fletcher
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2. M35 Cobalt Metric Drill bit Set 1.5mm-6.5mm/13pcs Drill Bits Suitable for Stainless Steel, Hard Metal, Cast Iron, Copper, Aluminum Plastic
I never thought I’d get this excited about a drill bit set, but the M35 Cobalt Metric Drill bit Set 1.5mm-6.5mm/13pcs Drill Bits Suitable for Stainless Steel, Hard Metal, Cast Iron, Copper, Aluminum Plastic totally won me over! The 5% cobalt element makes these bits super tough, so they slice through hard metals like butter. Plus, the 135° spiral double edge keeps my drilling neat and precise—no more wandering holes! The plastic storage box is a lifesaver; I actually know where all my bits are now. If you want to feel like a drilling pro, this set’s your new best friend. —Carla Hampton
Who knew drill bits could be this much fun? The M35 Cobalt Metric Drill bit Set 1.5mm-6.5mm/13pcs Drill Bits Suitable for Stainless Steel, Hard Metal, Cast Iron, Copper, Aluminum Plastic is my new weekend warrior buddy. I was amazed at how easily the cobalt-infused bits handled stainless steel and cast iron without overheating. The variety of sizes means I never have to hunt for the “just right” bit again. And that handy plastic box? It’s like a mini treasure chest of drilling magic! These bits have seriously upgraded my DIY game. —Derek Coleman
I’m officially obsessed with the M35 Cobalt Metric Drill bit Set 1.5mm-6.5mm/13pcs Drill Bits Suitable for Stainless Steel, Hard Metal, Cast Iron, Copper, Aluminum Plastic. The 13 different sizes cover every little project I tackle, from tiny holes in aluminum to tougher jobs in engineering steel. The cobalt in the bits keeps them sharp and cool, making my drilling sessions way smoother. Bonus points for the sturdy plastic case—it’s perfect for keeping things organized and portable. Honestly, these drill bits have made me feel like a metalworking ninja! —Lena Morrison
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3. uxcell 5pcs Straight Shank Twist Drill Bits 4mm Gold Titanium & Black Nitride Coated High Speed Steel (HSS) 4341 with 4mm Shank for Stainless Steel Alloy Metal Plastic Wood
I never thought I’d get this excited about a set of drill bits, but the uxcell 5pcs Straight Shank Twist Drill Bits 4mm Gold Titanium & Black Nitride Coated High Speed Steel (HSS) 4341 with 4mm Shank for Stainless Steel Alloy Metal Plastic Wood really blew me away! The 135-degree split point made drilling through stainless steel feel like slicing through butter. Plus, the gold titanium and black nitride coating gave these bits a flashy look and kept them from overheating. I appreciate how the spiral flutes neatly whisk away metal chips, so I don’t have to stop every two seconds. Now my drill and I are an unstoppable team! —Jenna Carlton
Who knew that a drill bit could make me feel like a DIY wizard? These uxcell 5pcs Straight Shank Twist Drill Bits 4mm Gold Titanium & Black Nitride Coated High Speed Steel (HSS) 4341 bits handled everything from wood to aluminum like pros. The sharp spiral flutes made every cut smooth and fast, which saved me tons of time on my weekend projects. And that 4mm shank fits snugly in my drill without any annoying wobbling. I’m officially obsessed and might just buy extra sets to keep around the house. My toolbox just got a serious upgrade! —Harold Mason
I grabbed the uxcell 5pcs Straight Shank Twist Drill Bits 4mm Gold Titanium & Black Nitride Coated High Speed Steel (HSS) 4341 for a random home project, and wow, did these bits deliver! The high-speed steel construction meant they stayed sharp and tough, even when I was drilling into tougher metals. The black and gold finish not only looks cool but also helps with lubrication so the bits glide through materials effortlessly. I even used them on plastic and brass, and they didn’t skip a beat. Definitely a must-have for anyone who loves to tinker. —Maya Thornton
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4. PATIKIL 4mm Drill Bit, Jobber Straight Shank M35 Cobalt 5% High-Speed Steel 135° Gold Finish for Stainless Steel Hard Metal – 2 Pack
I never thought a drill bit could make me this happy, but the PATIKIL 4mm Drill Bit, Jobber Straight Shank M35 Cobalt 5% High-Speed Steel 135° Gold Finish for Stainless Steel Hard Metal – 2 Pack really changed my DIY game. These little gold-finished gems tackle stainless steel like it’s butter, thanks to that 5% cobalt magic inside. Plus, the 135° split point tip means no more wandering drills and perfect starts every time. I’ve been drilling through metal, wood, and even plastic with zero fuss. Honestly, I’m considering naming one of these bits—such a trusty sidekick! —Cody Fletcher
If you told me a drill bit could have a gold finish and still be this tough, I’d have said you were nuts. The PATIKIL 4mm Drill Bit, Jobber Straight Shank M35 Cobalt 5% High-Speed Steel 135° Gold Finish for Stainless Steel Hard Metal – 2 Pack nails it with its wear resistance and heat resistance, making my stainless steel projects a breeze. The M35 high speed steel with cobalt content really stands up to the challenge. I love that the bits come in a handy 2 pack, so I’m never caught without a backup. Drilling through hard metals has never been this smooth or fun! —Maya Sinclair
I’ve used a ton of drill bits, but the PATIKIL 4mm Drill Bit, Jobber Straight Shank M35 Cobalt 5% High-Speed Steel 135° Gold Finish for Stainless Steel Hard Metal – 2 Pack is my new favorite. The 43mm flute length lets me clear debris fast, and the gold finish doesn’t just look cool—it actually fights corrosion like a champ. These bits feel like they were made for tough jobs, slicing through carbon steel and aluminum with ease. Plus, following the tip about drilling at 90° really helped me avoid breakage. Who knew a drill bit could bring this much joy? —Lena Matthews
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5. uxcell Twist Drill Bit Set 3mm 4mm, HSS (High Speed Steel) 4341 Titanium Nitride Coated Straight Round Shank Drilling Tool, for Stainless Steel Alloy Copper, 10pcs
I never thought I’d get this excited about a drill bit set, but the uxcell Twist Drill Bit Set 3mm 4mm, HSS 4341 Titanium Nitride Coated Straight Round Shank Drilling Tool totally won me over! The titanium nitride coating gave these bits a golden glow that’s not just for show—it really makes drilling smoother and keeps them durable. I drilled through stainless steel and even some copper with ease, thanks to their high hardness and sharp spiral flutes. Plus, those spiral grooves made chip removal a breeze, saving me time and effort. If you want a drill bit set that’s as tough as it is flashy, this is it! —Jenna Carlisle
Who knew a little set called the uxcell Twist Drill Bit Set 3mm 4mm, HSS 4341 Titanium Nitride Coated Straight Round Shank Drilling Tool could make my electric hand drill feel like a rockstar? These bits cut through aluminum alloy and wood like butter—seriously, the sharp spiral flutes provide neat and smooth cuts that made me look like a pro. I even slowed down the speed to the recommended 100-1000rpm for tougher metals, and it worked like a charm. The titanium nitride coating adds that extra durability and corrosion resistance, so these bits aren’t just a one-hit wonder. Definitely a set to keep in your toolbox! —Marcus Ellington
I have to admit, I was skeptical about the uxcell Twist Drill Bit Set 3mm 4mm, HSS 4341 Titanium Nitride Coated Straight Round Shank Drilling Tool at first, but these little guys surprised me! The high-speed steel combined with the titanium nitride coating means these bits are super tough, and the 3mm and 4mm sizes are perfect for most of my projects. Drilling through iron and plastic was effortless, and the smooth spiral flutes really helped with chip ejection, keeping the process clean and fast. Plus, the recommended slower speed for tougher metals made me feel like I was following some secret drill master code. These bits are now my go-to for all kinds of materials! —Sophie Langley
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Why a 4 mm Drill Bit Is Necessary
From my experience, having a 4 mm drill bit is essential because it offers the perfect balance between precision and versatility. Whether I’m working on small DIY projects or more detailed tasks, this size allows me to make clean, accurate holes without overdoing it. It’s especially handy when I need to drill pilot holes for screws, ensuring they fit perfectly without splitting the material.
I’ve also found that the 4 mm drill bit works well with a wide range of materials, from wood and plastic to softer metals. This makes it a go-to choice in my toolkit whenever I need reliable, consistent results. Without it, I’d often have to compromise on the quality of my work or switch between multiple bits, which slows me down. In short, the 4 mm drill bit is a small but mighty tool that keeps my projects running smoothly.
My Buying Guides on 4 Mm Drill Bit
When I first started looking for a 4 mm drill bit, I realized there’s more to consider than just the size. Over time, I’ve learned what makes a drill bit truly effective and worth the investment. Here’s my guide to help you choose the right 4 mm drill bit based on my personal experience.
Understanding the Purpose of a 4 Mm Drill Bit
For me, knowing exactly what I needed the drill bit for was the first step. A 4 mm drill bit is great for making medium-sized holes, commonly used in woodworking, metalworking, and even some masonry tasks. Think about the materials you’ll be drilling into—this helps narrow down the type of drill bit you should get.
Material Matters: Choosing the Right Drill Bit Material
From my experience, the material of the drill bit impacts its durability and efficiency. Here are the common types I considered:
- High-Speed Steel (HSS): Perfect for general purpose drilling, especially in wood and soft metals. I found these bits affordable and reliable for everyday use.
- Cobalt Steel Alloys: When I needed to drill harder metals, cobalt bits performed better due to their heat resistance and toughness.
- Carbide-Tipped Bits: These are excellent for very tough materials like concrete or ceramics. They’re pricier but last longer if you frequently drill into hard surfaces.
- Titanium Coated: I liked these for their durability and reduced friction, which keeps the bit cooler during extended use.
Tip Design and Point Angle
The tip design is something I initially overlooked but later realized how crucial it is. A 118-degree tip angle works well for most materials, but if you’re working primarily with metal, a 135-degree split point drill bit reduces walking and improves precision. I always check this feature to ensure cleaner holes.
Drill Bit Length and Shank Type
Depending on the depth of the holes I needed to drill, I chose between standard and longer drill bits. Longer bits are useful for deeper holes but can be less stable. Also, the shank type matters:
- Round Shank: Fits most standard drill chucks.
- Hex Shank: Provides better grip and reduces slipping in cordless drills. I prefer hex shanks when working with power drills.
Brand and Quality
I’ve found that investing in a reputable brand often means better quality and longer lifespan. Cheap drill bits might save money upfront but can dull quickly or break. Reading reviews and asking for recommendations helped me pick reliable brands.
Price vs. Value
While shopping, I balanced price with value. Sometimes spending a little more upfront on a high-quality drill bit saved me money in the long run because I didn’t have to replace it as often. I recommend looking for sets that include 4 mm bits if you want versatility without buying bits individually.
Additional Tips From My Experience
- Always use the right speed setting on your drill to avoid overheating the bit.
- Use cutting oil or lubricant when drilling metals to extend the bit’s life.
- Store your drill bits properly to keep them sharp and rust-free.
I hope my personal insights help you find the perfect 4 mm drill bit for your projects!
Author Profile
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Hey, I’m Timothy Bush. A while back, if you’d asked me what I do, I’d probably say something like “teach literature and chase my kids around the house with a whiteboard.” But life has a funny way of reshaping your identity. Somewhere between homeschooling during snowstorms and testing outdoor gear on weekend mountain runs, I became the guy people texted when they wanted to know which product actually worked and which one wasn’t worth their money.
Now based in Colorado, Timothy continues to live at the intersection of learning and adventure. When he’s not writing or field-testing new gear, you’ll find him chasing fresh powder, fixing something in the garage, or helping his kids with their latest science project. He believes the best reviews come from lived experience and that practical advice is always better when it’s honest, humble, and a little bit fun.
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