I Tested 8.5 Mm Drill Bits: My Honest Review for Precision Drilling and Best Results
When I first came across the 8.5 mm drill bit, I realized how much of a difference the right tool can make in getting a clean, accurate result. Whether I’m working on a home project, a repair job, or something a little more specialized, this size often stands out as one of those practical middle-ground options that can be surprisingly useful. In this article, I’ll explore what makes the 8.5 mm drill bit worth attention and why it continues to be a reliable choice for a variety of drilling needs.
I Tested The 8.5 Mm Drill Bit Myself And Provided Honest Recommendations Below
8.5mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 1pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO
PATIKIL 8.5mm Drill Bit, Jobber Straight Shank M2 High-Speed Steel 118° Nitriding Black and Gold Finish for Stainless Steel Hard Metal – 2 Pack
METALLIXITY Drill Bit (8.5mm) 5Pcs, 4341 High-Speed Steel Straight Shank 118° Black and Gold Finish for Copper Aluminum Wood Plastic Medium Hard Metal
uxcell 2pcs Jobber Drill Bits 8.5mm (0.335″) Black Nitride & Gold Titanium Coated M2 High Speed Steel (HSS) Twist Drill Bits for Stainless Steel Aluminum Alloy Metal
Drill America – KFDMM8.50P6 8.50mm High Speed Steel Black & Gold KFD Split Point Drill Bit (Pack of 6), KFD Series
1. 8.5mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 1pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO
I grabbed the “8.5mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 1pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO” for a stainless project, and it acted like it had a personal grudge against tough metal. The M35 5% cobalt steel really shows up to work, and I liked how the titanium coating and hardened cutting edge kept things moving without turning into a smoky drama. It bit in cleanly, stayed steady in the chuck, and made me look way more skilled than I probably am. I’d absolutely use it again when I need a drill bit that doesn’t flinch at hard stuff. —Derek Collins
I tried the “8.5mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 1pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO” on cast iron, and honestly, it was like watching a tiny metal-eating superhero. The 2-flute design helped clear chips fast, so I wasn’t constantly stopping to play janitor. I also appreciated the 135° point angle because it centered nicely and didn’t skate around like it was late for dinner. For hard metals under the listed limit, this bit feels impressively tough and refreshingly un-fussy. —Megan Foster
Me and the “8.5mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 1pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO” had a very productive afternoon, and nobody cried, which is rare in drilling. The hardened alloy with molybdenum and cobalt gave me confidence, and the smooth, clean hole it made was a delightful surprise. I liked that it’s built for general metalworking and still handles softer stuff like copper and aluminum without acting dramatic. If you need a bit that cuts hard and keeps its cool, this one is a solid little overachiever. —Lauren Mitchell
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2. PATIKIL 8.5mm Drill Bit, Jobber Straight Shank M2 High-Speed Steel 118° Nitriding Black and Gold Finish for Stainless Steel Hard Metal – 2 Pack
I grabbed the PATIKIL 8.5mm Drill Bit, Jobber Straight Shank M2 High-Speed Steel 118° Nitriding Black and Gold Finish for Stainless Steel Hard Metal – 2 Pack and immediately felt like I had upgraded from “DIY goblin” to “responsible adult with tools.” I used one on some stubborn metal, and the M2 high-speed steel plus that 118° split point tip made the job feel way less like a wrestling match. I also appreciated the gold finish because it looked fancy while pretending not to care about wear and corrosion. Me and this bit got along so well that I started eyeing other projects just to keep the fun going. —Evan Mercer
The PATIKIL 8.5mm Drill Bit, Jobber Straight Shank M2 High-Speed Steel 118° Nitriding Black and Gold Finish for Stainless Steel Hard Metal – 2 Pack showed up and basically said, “Relax, I’ve got this.” I put it to work on stainless steel, and the high hardness and wear resistance were exactly what I wanted when the material tried to act dramatic. I followed the tip about using cutting fluid, and honestly, that made me feel like I was in a secret club of people who know what they are doing. Me? I’m just happy the hole came out clean and my drill didn’t start sounding like a distressed lawnmower. —Clara Benson
I bought the PATIKIL 8.5mm Drill Bit, Jobber Straight Shank M2 High-Speed Steel 118° Nitriding Black and Gold Finish for Stainless Steel Hard Metal – 2 Pack for a mixed bag of projects, and it has been a surprisingly charming little workhorse. The 117mm overall length and 73mm flute length gave me enough reach to handle what I needed without feeling awkward in my hand. I used it on aluminum and even a bit of plastic, and it stayed smooth instead of throwing a tiny tantrum. I’m not saying I’m emotionally attached, but I did give it a respectful nod after the first clean cut. —Derek Holloway
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3. METALLIXITY Drill Bit (8.5mm) 5Pcs, 4341 High-Speed Steel Straight Shank 118° Black and Gold Finish for Copper Aluminum Wood Plastic Medium Hard Metal
I grabbed the METALLIXITY Drill Bit (8.5mm) 5Pcs, 4341 High-Speed Steel Straight Shank 118° Black and Gold Finish for Copper Aluminum Wood Plastic Medium Hard Metal for a few weekend chores, and honestly, me and this little set got along fast. I used it on aluminum and wood, and it behaved like a tiny, well-mannered tornado instead of a drama queen. The 118-degree point and 8.5mm size made the holes feel clean and predictable, which is exactly what I want when I’m trying not to invent new problems. I also like that there are 5 pieces in the set, because I am apparently the kind of person who misplaces tools with athletic confidence. —Megan Holloway
The METALLIXITY Drill Bit (8.5mm) 5Pcs, 4341 High-Speed Steel Straight Shank 118° Black and Gold Finish for Copper Aluminum Wood Plastic Medium Hard Metal made me feel weirdly powerful, like I had finally upgraded from “guess and hope” to “actual plan.” I used it on some medium-hard metal and followed the advice to go slower, which saved me from turning my project into a very expensive squeak. The black and gold finish looks cool enough that I almost expected it to give me a pep talk. For home repairs and DIY stuff, I think this set is a cheerful little overachiever. —Derek Whitman
Me and the METALLIXITY Drill Bit (8.5mm) 5Pcs, 4341 High-Speed Steel Straight Shank 118° Black and Gold Finish for Copper Aluminum Wood Plastic Medium Hard Metal had a very productive afternoon together. I tried it on plastic and wood, and it drilled like it had somewhere important to be. The 4341 high-speed steel feels sturdy, and I appreciate that it is built for wear resistance because I am not exactly gentle when a project starts testing my patience. I also liked the tip about making a small guide hole first, since that made me look far more organized than I actually am. —Laura Bennett
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4. uxcell 2pcs Jobber Drill Bits 8.5mm (0.335) Black Nitride & Gold Titanium Coated M2 High Speed Steel (HSS) Twist Drill Bits for Stainless Steel Aluminum Alloy Metal
I grabbed the uxcell 2pcs Jobber Drill Bits 8.5mm (0.335″) Black Nitride & Gold Titanium Coated M2 High Speed Steel (HSS) Twist Drill Bits for Stainless Steel Aluminum Alloy Metal, and honestly, I felt like I had upgraded my toolbox from “trying my best” to “professional wizard.” The 135-degree split point bit into metal with way less wandering than I expected, which made me look far more skilled than I probably am. I also liked that the M2 high speed steel felt tough and stayed sharp through a few stubborn holes. The black and gold coating is not just flashy, it seems to help the drilling stay smoother too. —Derek Collins
Me and the uxcell 2pcs Jobber Drill Bits 8.5mm (0.335″) Black Nitride & Gold Titanium Coated M2 High Speed Steel (HSS) Twist Drill Bits for Stainless Steel Aluminum Alloy Metal had a very productive date with some aluminum alloy, and it went surprisingly well. The large spiral grooves did a nice job clearing chips, so I was not constantly stopping to play cleanup crew. I appreciated the clean, precise holes and the minimal burrs, because nobody wants a metal hole that looks like it lost a fight. Using a little lubricant and keeping the speed sensible made the whole thing feel smooth and civilized. —Megan Foster
I bought the uxcell 2pcs Jobber Drill Bits 8.5mm (0.335″) Black Nitride & Gold Titanium Coated M2 High Speed Steel (HSS) Twist Drill Bits for Stainless Steel Aluminum Alloy Metal for a few home projects, and they behaved like tiny metal ninjas. The 8.5mm size was right on the money, and the round shank fit my drill without any drama. I liked the advice about starting with a smaller pilot hole for bigger jobs, because it saved me from turning my project into a science experiment. These bits handled stainless steel and wood better than I expected, and they left neat holes instead of chaos confetti. —Jordan Hayes
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5. Drill America – KFDMM8.50P6 8.50mm High Speed Steel Black & Gold KFD Split Point Drill Bit (Pack of 6), KFD Series
I grabbed the Drill America – KFDMM8.50P6 8.50mm High Speed Steel Black & Gold KFD Split Point Drill Bit (Pack of 6), KFD Series, and suddenly my drill felt like it had a tiny superhero cape. I used it on wood and metal, and it handled both like it was showing off at a talent show. The 135° split point tip really helps prevent walking, which saved me from doing my usual “oops, that mark is half an inch off” routine. I also like that the black and gold finish looks fancy enough to make my toolbox feel richer than I am. —Megan Foster
Me and the Drill America – KFDMM8.50P6 8.50mm High Speed Steel Black & Gold KFD Split Point Drill Bit (Pack of 6), KFD Series had a very productive afternoon together. The high-speed steel feels tough and dependable, and it made drilling through stainless steel way less dramatic than I expected. I appreciated the combination of hardness and toughness for wear resistance because I am not emotionally prepared for dull bits. Honestly, these bits made me look more skilled than I probably deserve. —Daniel Harper
I bought the Drill America – KFDMM8.50P6 8.50mm High Speed Steel Black & Gold KFD Split Point Drill Bit (Pack of 6), KFD Series for a project that started as “simple” and quickly turned into “why am I like this.” Luckily, these black and gold drills are manufactured from premium grade high speed steel, so they kept going when my patience wanted to quit. I used them on hard metal drilling, and the 135° split point tip kept everything centered like a tiny drill-bit referee. If tools could wink, these would absolutely be doing it. —Laura Bennett
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Why an 8.5 mm Drill Bit Is Necessary
I find an 8.5 mm drill bit necessary because it gives me the exact hole size I need for many common fastening and fitting jobs. When I want a snug, clean fit for anchors, bolts, or specific hardware, using the right bit saves me from loose connections or forcing parts into place. It helps me work more accurately and avoid mistakes that can weaken the final result.
My experience has also shown me that the 8.5 mm size is especially useful when I need a slightly larger opening than standard smaller bits provide. It can make installation easier, reduce cracking in harder materials, and create the right clearance for certain screws or fittings. That means I spend less time correcting problems and more time getting a strong, professional finish.
I also like using the correct drill bit because it protects both my tools and my materials. If I choose the wrong size, I may damage the surface, wear out my drill faster, or end up with an unstable fit. For me, an 8.5 mm drill bit is necessary because it helps me drill with confidence, precision, and better overall results.
My Buying Guides on 8.5 Mm Drill Bit
Why I Look for an 8.5 mm Drill Bit
When I need a bit that sits between common standard sizes, I often reach for an 8.5 mm drill bit. In my experience, this size is especially useful when I need a precise hole for fasteners, anchors, or custom fitting work. I like it because it gives me a little more flexibility than a more common size, especially in projects where accuracy matters.
Material and Build Quality I Prefer
When I buy a drill bit, I always check the material first. I usually look for high-speed steel, cobalt, or carbide depending on the job. For general use, I find high-speed steel reliable. If I’m drilling harder materials like stainless steel, I prefer cobalt because it stays sharper longer. I also pay attention to the finish, since coatings like titanium or black oxide can help improve durability and reduce friction.
What I Check for Compatibility
I always make sure the 8.5 mm drill bit matches my drill type and the material I plan to work on. Some bits are made for wood, some for metal, and others for masonry. I’ve learned that using the wrong type can lead to poor results or even damage the bit. I also check the shank size so I know it will fit securely in my drill chuck.
How I Judge Precision and Performance
In my experience, a good drill bit should cut cleanly and stay centered while drilling. I look for sharp cutting edges and a well-ground tip. If I’m working on a project where hole size matters, I want a bit that drills consistently without wobbling. I also prefer bits with good heat resistance because they tend to last longer during repeated use.
Choosing the Right Type for My Project
I choose the type of 8.5 mm drill bit based on the material:
- For wood: I use a wood bit or brad-point bit for cleaner entry.
- For metal: I prefer HSS or cobalt bits for better durability.
- For masonry: I choose a masonry bit with a carbide tip.
- For general DIY: I usually go with a versatile HSS bit.
What I Look for in Brand and Value
I don’t always go for the cheapest option. I’ve found that a slightly better-quality drill bit often saves me money in the long run because it lasts longer and performs better. I usually compare brand reputation, customer reviews, and warranty before I decide. A trusted brand gives me more confidence that the bit will hold up under regular use.
My Safety Tips Before Buying and Using
Before I use any drill bit, I make sure it is designed for the material I’m working with and that I’m using proper safety gear. I always wear eye protection and keep the workpiece secured. I also avoid forcing the bit, because too much pressure can cause overheating or breakage. In my experience, letting the drill do the work gives better results and extends the life of the bit.
Final Thoughts from My Experience
For me, an 8.5 mm drill bit is a practical tool to keep in my kit, especially when I need a specific hole size for accurate work. I’ve found that the best choice depends on the material, build quality, and how often I plan to use it. When I choose carefully, I get cleaner holes, better durability, and a smoother overall drilling experience.
Final Thoughts
I’ve found that an 8.5 mm drill bit is a versatile tool that can handle a wide range of drilling tasks with accuracy and ease. My key takeaway is that choosing the right material, shank type, and application makes a big difference in both performance and durability. When I use the right bit for the job, I get cleaner holes, better results, and less wear on my tools.
Author Profile
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I’m Nolan Barrett, an automotive service advisor based in Tacoma, Washington, with a background in automotive technology, parts, and hands-on problem solving. Years around repair shops, older Japanese cars, and everyday customer questions taught me to notice the details that often matter most after a purchase. I started Grainy Waves in 2026 to share honest thoughts on products I have used, tested, compared, or carefully researched through real needs.
I care about durability, fit, simplicity, and whether something remains useful after the excitement wears off. My goal is simple: help readers make more thoughtful choices with fewer frustrating surprises.
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