Countersink Drill Bit Set for Steel, 3 Flute 90 Degree HSS Chamfering Tool Bit for Metal Wood Woodworking Metal Working Tool Bit Set, Pack of 6pcs 1/4 1/2

Awesome countersinks , use oil for best results. I used them for mild steel and was surprised at the results. Not sure how long they will last though

Works well, excellent value.

I bought this to drill some countersink holes in an aluminum plate I bought to use as a heated bed on my 3D printer (713maker). I'm an idiot and used the wrong one to countersink the holes for my standard M3 screws (there's 2 for M3), so that's my fault. However, it got the job done with my Ryobi hand drill as you can see in the pictures. While it did get the job done it did come out a little ugly. However, that could be due to the fact that I used a hand drill instead of something like a drill press. I didn't need it to be fancy, just functional, and for that it worked. I also used some 3 in 1 oil. Wasn't sure if I was supposed to or not, but I've seen other metal shops use oil so I figured why not. The bits went through the aluminum like butter. Can you tell I'm not a metal worker?

Great tool for the price

I used it once on metal L bars and it worked good for the first 5 holes but after that, it smoked and got dull. If you need something for professional use, this is not it.

I'm an old fashion machinist, and learned long ago to drill-counter sink at low speed-300 to 500RPM, when countersinking metal. The harder the material, the lower the speed, to avoid "chattering" of the bit. Soft stuff like wood or plastic can tolerate much higher speed. Trying to countersink metal with a power hand drill, requires a very strong handed He-man.

Each item in this set came well machined and with perfectly straight shafts. I have used them on both steel and aluminum with good results. They leave a smooth finish that requires no additional “clean up” and none of the pieces shows any wear so far. I did not rate longevity and durability solely because I haven’t had the set long enough. That said the total lack of wear exhibited by the bits so far strongly suggests to me that durability and longevity are unlikely to be an issue. And, to be honest, given that they perform so well, at this price I’m really not concerned about longevity. (As long as they’re still available if I need to replace them of course!!!) P.S. No inducement received for this review.

First of all, per the listing image (first image shown in my review here. It shows 6.1mm - 6.4mm - 10.4mm and so on… I needed the 10.4mm.. however, as you can seen in the second image of what I received, literally only 2 of the bits are engraved with the actual bit size on them… and even wilder is that the smallest size says “6.1” which contradicts the listing image size!… so I have to guess which one is the 10.4mm AND just hope that it even is 10.4mm as shown in the listing image… this might be the worst quality item I’ve received from amazon. How does this even end up making it out the factory?..

After few months in my drawer I have discovered that these countersink bits are ineffective in cutting a countersink into cedar, let alone a hardwood or ply. I can't call them blunt, because they haven't been used. It seems that the cutting edge hasn't been manufactured to stand proud of the leading edge such that the tool can cut into material effectively.