Question 1

Are these bits truly suitable for drilling stainless steel, or will they ruin the metal and the bit?**

Accepted Answer

Yes, they are well-suited for stainless steel, which is a key strength noted in many reviews. The M35 cobalt steel composition handles the hardness well. The critical tip from experienced users is to always use a lubricant like cutting oil, drill at a slow speed, and apply steady pressure to avoid work-hardening the stainless steel, which can damage any drill bit.

Question 2

I mostly work with wood and plastic. Is this overkill, or is it a good all-around set?**

Accepted Answer

It's an excellent, durable all-around set. While you could use less expensive bits for only wood, the extreme sharpness and 135-degree tip of these bits provide cleaner, faster holes with less splintering in wood and plastic. Many DIYers on platforms like TikTok appreciate having one robust set that can handle everything from a metal bracket to a wood shelf without switching.

Question 3

What's the real difference between this M35 set and more expensive "cobalt" bits?**

Accepted Answer

M35 steel contains about 5% cobalt, enhancing heat resistance and hardness over standard HSS bits. More expensive sets often use M42 steel (8% cobalt) for maximum heat resistance in continuous professional use. For most home garages and shops, M35 offers fantastic performance and value. As some Reddit users note, expecting this set to perform like premium industrial bits on the toughest alloys may lead to disappointment.

Question 4

I've read some comments about bits breaking. What are they typically being used for when this happens?**

Accepted Answer

Isolated breakage reports usually involve extreme scenarios: drilling very thick (>1/2"), high-tensile steel (like axles or certain tool steels) without adequate lubrication, or using excessive side pressure. For general hardened metal, cast iron, and stainless steel projects—even in automotive repair—the bits perform reliably. Always ensure your drill is not in "hammer" mode for metal and use a pilot hole for larger diameters.

Question 5

How is the storage case, and what if a bit breaks or the case fails?**

Accepted Answer

The indexed plastic case is highly praised for organization, though a small number of users have reported the latch or hinge can become fragile with rough job-site handling. The bits are standard jobber length, so they can be stored in any drill index. Regarding breakage, it's best to contact the seller or GMTOOLS support directly for warranty assessment, as policies can vary based on the point of purchase.

GMTOOLS 13Pcs Cobalt Drill Bits Set, M35 HSS 135 Degree Tip, Twist Jobber Length Drill Bit Kit for Hardened Metal, Cast Iron, Stainless Steel, Plastic and Wood with Storage Case 1/16"-1/4"

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