Hymnorq 10-Piece M35 Cobalt Steel Drill Bit Set for Metals – 4mm Diameter, Dual Twist Flute, 135° Split Point, Bronze Hue Finish, Straight Shank, Chamfered End, PP Plastic Case

I ordered 5 because I was unsure how durable they would be...I was pleasantly surprised! I drilled sooooo many holes building my overland trailer and these 5 bits did their job with the help of a little oil they held up well. Are they the sharpest? No. But I did not break a single one. Just takes a bit of patience.

good set of smaller metric bits

I have bought three of these sets . The drill bits are superior ! They used to come in better cases, but the case is pretty irrelevant for the most part -- it just acts as an index.

At the time I purchased these, I only intended to use them for light duty (drilling into polymer). However, as fate would have it, I had to use them to drill into hardened steel, and much to my surprise, they performed admirably. It was a pleasant surprise (I was expecting "Chinese junk") and I'm very happy with this purchase; especially considering that it's a METRIC set, which is difficult to find (in the USA). I wish the set had a 1mm bit, but oh well. It's just a preference, not anything against the quality of the bits in this set.=============Update 1/16/18=============My rating has changed from 5 stars down to 3. I needed to drill into metal again--actually I wasn't even drilling new holes, but just "chasing" already existing holes to expand them--and neither the 4.5mm or 4.8mm bits would do anything. They just spun around getting hot, without cutting anything. I even tried the 5mm bit, even though that was too big for my purposes, and it also did nothing but spin. Thus, I've used four of the bits (4, 4.5, 4.8, and 5mm), and only one of them did anything. The one that actually worked did its job well; the others are a HUGE disappointment.=============Update 1/25/18=============Kudos to Migiwata customer service (thank you, Bella!). After hearing about my not-so-pleasant experience with these bits, they sent me a second set. Apparently their original supplier had run dry, and they had to use a second, temporary supplier while the original caught up with demand. The first set that I received was from the temporary supplier. The new set is from the original supplier, and the bits seem to be in order in this new set. So how do you tell the difference? By the case (see photos). The set with the blue dot on the case--which is a plastic retainer to keep the case closed--is from the original supplier. Now if you happen to get a set without the blue dot, don't panic. Just because I got a subpar set that slipped through the manufacturer's quality control process doesn't mean that you did, too. Try the bits out first. WORST case is that Migiwata customer service takes care of you like they did me; best case is you don't even have a problem. As for me and my review of this product, I'm a happy camper again and am bumping my rating back up to 5 stars. The bits are great (make sure to use a good cutting lubricant/coolant) and Migiwata customer service is stellar.

Arrived on time and as described. Works well.

The 5 mm drill bit was essential repairing a broken 6 mm fastener securing the oil pan to the engine block. After an unsuccessful attempt to remove the bolt using a left hand drill bit and extractor, it was time to drill through the middle of the fasterner, the steel engine block, and tap new threads using an 6 mm x 1 Irwin tap. Adhering to the 60 percent rule of thumb of drilling 60 percent of the actual hole required, a 5.20 or 5.25 mm drill bit was needed, however this drill bit set had 5.0 and then 5.5 mm drill bits in its range. Using the 5.0 drill bit and cutting oil, the drill bit drilled nicely through the bolt and engine steel block. The drill bit did not wobble off center. The Irwin 6 mm x 1 tap from the metric tap and die set purchased from Amazon and using cutting oil cut new threads with ease. I was careful to only cut new threads applying no more than 1/4 or less clockwise turns and then reversing counter clockwise a 1/4 turn. Halfway through the tap I removed the tap completely from the hole, removed the metal shavings using cutting oil, and finished the tap. Installed the new oil pan gasket with the oil pan and torqued the bolts using a Carlyle torque wrench from Napa Parts store to 105-inch pounds. Vehicle back in action. Thanks Migiwata for your metric drill bits. I recommend using this set.

I can't say that they are as god as "Carbaloy" drills or that they are not. I used them on a very tough saw blade and they seemed to loose cutting ability quickly. The Carbaloy drills might not have worked any better but they were not of the size I needed. I did get the hole that I wanted but used drills of differing sizes to expand the hole when the right sized drill stalled before penetration. For the price, though they were fine. This was a metric set and the hole size was not important as long as it gave clearance. You might need SAE size holes and drills for finer work. I'd rate them higher if I had a standard against which to measure them, as they were of good quality manufacture.

You never know how good or bad a drill bit is going to be till you buy it and try it. Hymnorq M35 Cobalt drill bits have been the real deal for me. I've purchased multi-packs of larger daimeter and smaller diameter Hymnorq M35 Cobalt bits that have worked just as well as these 4.2mm bits. Hymnorq M35 cobalt bits are reasonably priced, cut fast, and stay sharp (I do try to take care of them regarding matching RPM to bit diameter and keeping cutting oil on the bits as much as possible). As long as I can continue to find this family of drill bits, I'll continue to replenish my toolboxes with them.