amoolo M35 Cobalt Drill Bits 15/64" - 5pc Jobber-Length, 135° Split Point for Stainless Steel

These are five M35 cobalt 15/64" jobber-length twist drill bits engineered to cut hard metals like stainless steel with reduced walking and improved wear resistance.

amoolo's 15/64" cobalt drill bit set (5 pieces) is built from M35 high-speed steel containing 5% cobalt, offering higher heat tolerance and longer life than ordinary HSS bits. Each bit features a fully ground flute and a 135° split point to evacuate chips quickly, reduce friction, and start holes cleanly without a center punch. Designed for general-purpose and heavy-duty metalworking, the set fits most standard drills and is useful on stainless steel, alloy steel, cast iron, aluminum, and softer materials when used with proper speed and cooling.

How do these bits hold up when drilling stainless steel?

The M35 cobalt composition raises hardness and heat resistance, so the 15/64" bits keep cutting edges longer under high-temperature conditions than plain HSS. The 135° split point reduces walking and helps maintain concentric holes on hard surfaces.

• 5% cobalt content improves wear resistance during sustained drilling.
• Split-point tip starts quickly without a pilot or center punch.
• Fully ground flutes evacuate chips and lower friction and heat buildup.

What drilling performance can I expect for different materials?

These jobber-length bits are versatile: they excel on hard metals and remain effective on softer materials when used at appropriate speeds and with coolant or cutting oil. Adjust feed and RPM for material hardness to maximize life and hole quality.

• Stainless steel and alloy: use moderate speed, steady feed, and cutting fluid.
• Cast iron and steel: slower speeds and intermittent pecking reduce heat.
• Aluminum, wood, and plastics: higher speeds and light pressure for clean holes.

How does the design reduce bit walking and improve hole accuracy?

The 135° split point forms two small cutting lips that bite immediately into the workpiece, which minimizes lateral slippage at startup. The straight shank and precise grinding keep the bit centered in standard chucks for more accurate holes.

• Split-point geometry eliminates the need for an initial center punch in many cases.
• Straight shank fits securely in chucks to maintain concentric rotation.
• Balanced flute grinding reduces vibration and improves hole finish.

What care and usage tips extend the life of cobalt drill bits?

Proper speed, steady pressure, and coolant are the primary ways to lengthen tool life when drilling metals. Avoid excessive feed that overloads the tip and use intermittent drilling on deep holes to clear chips and cool the cutting edge.

• Use cutting oil for stainless steel and high-alloy steels to reduce heat.
• Lower RPMs for hard metals; increase speed for soft metals like aluminum.
• Retract occasionally on deep holes to clear chips and prevent clogging.

Who is this for: The amoolo 15/64" cobalt drill bit set is aimed at metalworkers, automotive technicians, machinists, and serious DIYers who need durable bits for drilling hardened metals and stainless steel. If you frequently drill tough alloys or want longer-lasting performance than standard HSS bits, this five-piece set supplies purpose-built geometry and material to handle demanding shop and field tasks.