Cobalt Drill Bit Set, 5/16" (10pcs) M35 High Speed Steel Jobber Length Drill Bit Kit for Hardened Metal, Stainless Steel, Cast Iron, Wood and Plastic, with Index Storage Case

Bastante satisfecho con la duración, es similar a las brocas Milwaukee titanio pero a un precio menor para ser de cobalto esperaba que duraran un poco más pero aun así muy satisfecho

I bought a 10 pack because where I needed to use them, there was no store to buy replacements if it turned out these were junk. In the end, these (this) bit was as pleasant surprise. I drilled 30 holes in a steel I-beam with only needing a single bit and it still drills effectively without needing excessive force. The holes were drilled fast and easily with clean breakout on the backside. The drill bit cutting edge was does show some damage (see closeup image) after the 30 holes but it still drills effectively. I have no doubts the bit would drill another 10 holes on the same bit. I am surprised there is rust on the cutting edge since the HSS and cobalt is pretty rust resistant… I wouldn’t expect rust after sitting just a single day. The hardness of the bit must vary from the tip (very hard) to the shank end (soft) since there is a lot of damage where the bit slipped in the drill jaws a couple times (see close-up). Whatever the hardness range is, I’m happy with the combination of hardness and ductility and the overall drilling results. The bits come in a nice plastic case that can expand in length so it will hold a variety of bits including longer bits. The case opens easily to grab a replacement (I didn't need to) and closes tightly enough to not worry about spilling any. The case is right sized and not too big for the typical handful of bits needed. Overall, I'm very happy with these bits.

Nothing

No era lo que esperaba muy caras y son de medida muy pequeñas, no llegan ni alos 10mm. Yo buscaba de 8mm. sta 14mm. Pero la descripción está muy confusa

Works well