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 needed to install a roof rack on my truck which required drilling 12 holes in the roof. Once I got started, I discovered that I had to drill through 2 layers to get the appropriate depth, not just one. But this drill bit went through the second layer just easily as the first. I ended up with 12 very clean holes. They were perfectly sized, as the inserts I was using went in nice and snug.If you're needing to drill for a GM truck roof rack, the this is the correct size drill bit for the Rivnut inserts. My roof rack is holding very well, because this drill bit made the right size holes for it.

I used it for drilling brass. I drill an accurate diameter hole. It has a reasonable finish. I can add no other comments as it has not been used long enough to evaluate it.

Just a warning that this bit will not fit your 1/2” drill. My mistake so I didn’t ding on the rating. I didn’t send back since it was my dumb mistake.

While the drill bit appears to be very durable, it comes sharpened with a very shallow angle. This makes is a challenge to get started in steel and to get a clean hole and exit. I would prefer a steeper angle with a bit more "bite". Also, the price was a bit high for a single drill bit - prior purchase of a pair of similar bits was same price but for 2.

I needed a unique size bit for a special project, but could not find one locally. Assumed a mail order bit was not likely to be of the best quality, but I was pleasantly surprised to see the quality and have to function perfectly. I thin it will last longer than my use for it will last. That means I'll never have to buy a replacement.

I was looking for a drill bit to use before taping 6mm threads, Charts say use a 5.2mm drill, Wrong. If you use a 5.2mm drill then tap threads with a 6mm tap, you will only get 60% of the thread depth. I even tried slipping the 5.2mm drill into a hole that was taped to 6mm, it would not fit.

I bought this bit specically to drill the precise size hole for installing M6 rivetnuts. It did the job that it was purchased for.

Impossible to use unless you have a rotary hammer with a wanted to chuck because even a half inch hammer drill won't fit 14mm. I've never seen a big drill bit like this not be tapered down to fit a drill so I returned it because it's impossible to use

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