5mm Metric M35 Cobalt Steel Extremely Heat Resistant Twist Drill Bit of 2pcs with Straight Shank to Cut Through Hard Metals Such as Stainless Steel and Cast Iron, 5% Cobalt M35 Grade HSS-CO

I used the 8mm bit to drill 2 holes into the aluminum pole of a patio umbrella. Now the weighted base's hand-screws that secure the umbrella pole to the weighted base can go directly into the umbrella pole for a MUCH MORE secure fit, rather than just a friction hold. Now, the only way the umbrella pole will come out of the weighted base is if both hand-screws shear off at the same time. Which is highly unlikely.Secured the aluminum umbrella pole into a vice. Slowly drilled into the pole until I got a hole started. Then slowly applied more pressure and speed. By going slow and steady, the drill bit went through the aluminum pole very easily without an issue. 5/5 stars.

I had to drill lines of holes for 5mm fasteners along the work hardened edges of stamped 3mm thick steel parts. Because the material was so thin compared to the hole diameter, and because 2.4mm pilot holes had been pre-drilled (a mistake), the drill would catch every time it started to break through the material. In spite of having to reverse the drill multiple times and hit the material repeatedly each hole to break through, I got 64 holes drilled with only minor chipping on one flute of a single drill.

Perfect! Went through my aluminum bike frame like butter. I use this for riv-nuts. The nuts fit perfectly. Very sharp and good quality!

Sharp

Item arrived on schedule. I used it to drill through 1/8" 4130 steel which it did with ease and minimal chatter. I could see no wear after drilling four such holes. Not a comprehensive evaluation but it did what I needed.

As described

Good quality drill bits. Used them on 1/8 angle iron still hold their sharp edge, and yes lubrication helps to

Im drilling plastic - so this will last forever.