HSS Cobalt Jobber Drill Bit Set 1-10mm - 10 Pieces

 Specifications

Compatibility

Who Is This For?

The HSS Cobalt Jobber Drill Bit Set 1-10mm is aimed at tradespeople and professionals who regularly work with stainless steel, hard alloys, or high-tensile materials where standard HSS bits burn out or fail to cut cleanly. It suits maintenance engineers, metal fabricators, site fitters, and mechanical contractors working across construction, infrastructure, and industrial maintenance environments. The compact 10-piece format makes it equally at home in a site van toolbox and on a fabrication workbench.

Typical Applications

• Drilling fixing holes in stainless steel handrail systems, balustrade posts, and architectural metalwork

• Fitting brackets, cleats, and plates into structural steelwork on commercial and civil construction projects

• Maintenance drilling into machine frames, motor housings, and plant equipment made from alloy or high-tensile steel

• Creating clearance holes through aluminium profiles, extrusions, and sheet fabrications

• Electrical and mechanical installation work requiring accurate holes in mild steel and stainless steel enclosures

• Automotive and plant repair where drilling into hardened or heat-treated components is required

• General workshop use across the ten most common metric diameters without the need to change between sets

How to Use

1. Select the correct diameter for your application. For clearance holes, refer to the fixing manufacturer's recommended drill size.

2. Fit the selected bit into the drill chuck, seating it centrally and tightening the chuck jaws fully before switching on.

3. For stainless steel, alloy steels, and non-ferrous metals, apply a cutting lubricant to the bit tip before drilling. This reduces heat buildup and extends bit life considerably.

4. Set the drill speed to suit the material and diameter. Larger diameters require lower RPM. For stainless steel, use lower speeds than for mild steel to avoid work hardening the surface at the cutting zone.

5. Apply firm, consistent pressure. Avoid letting the bit spin without cutting, which will harden the surface of stainless steel and make drilling progressively more difficult.

6. Clear swarf regularly when drilling deeper holes to prevent chip packing in the flutes and overheating.

7. As the bit approaches break-through, reduce pressure to prevent snatching and protect both the workpiece and the bit tip on exit.

Safety and Maintenance

Safety during use:

• Wear impact-rated safety glasses or a full face shield when drilling metal. Flying swarf and bit fragments are a serious eye hazard.

• Secure the workpiece in a vice, clamp, or fixture before drilling. Do not hold metal workpieces freehand.

• Wear cut-resistant gloves when handling metal workpieces. Do not wear gloves near rotating chuck components.

• Bits become very hot in use, particularly when drilling stainless steel. Do not handle the bit immediately after use.

• Do not exceed the drill's rated capacity for the bit diameter in use.

After use and maintenance:

• Wipe all bits clean of swarf and cutting lubricant before returning them to the case.

• Inspect tips regularly for signs of wear, chipping, or blunting. M35 cobalt bits can be resharpened using a dedicated HSS drill sharpener, restoring performance close to original.

• Store bits in the supplied case to protect cutting edges from contact damage between uses.

• Do not store bits loose in a toolbox where tip-to-tip contact will cause rapid edge deterioration.

Frequently Asked Questions

Q: What is the difference between M35 cobalt HSS and standard HSS drill bits?

 A: Standard HSS (M2 grade) is suited to wood, plastics, and mild steel but loses its cutting edge quickly when drilling stainless steel or hard alloys because sustained heat softens the tool steel at the tip. M35 cobalt HSS contains 5% cobalt alloyed into the steel matrix, which raises its red hardness, the temperature at which the steel begins to soften under load. In practice, this means M35 cobalt bits maintain their cutting geometry for considerably longer when drilling heat-generating materials, giving cleaner holes and fewer bit changes on the job.

Q: What does DIN 338 mean and why does it matter when buying a drill bit set?

 A: DIN 338 is a German industrial standard widely adopted across the UK and Europe that defines the dimensions, tolerances, and geometry of jobber-length twist drill bits. A bit manufactured to this standard must conform to specified values for shank diameter, flute length, overall length, point angle, and helix angle. For a buyer, DIN 338 compliance means the bits will seat and run true in any standard chuck, that geometry is consistent across every diameter in the set, and that sizes are interchangeable with jigs, guides, and tooling that reference the same standard. It is a reliable quality indicator when comparing drill bit sets at different price points.

Q: Can I use the HSS Cobalt Jobber Drill Bit Set 1-10mm on stainless steel?

 A: Yes, stainless steel is the primary application that drives most purchases of M35 cobalt bits. Technique matters as much as the bit grade: use a cutting lubricant at the tip, keep RPM lower than you would for mild steel, and maintain consistent feed pressure to avoid the bit spinning without cutting. Allowing the bit to spin without cutting work-hardens the surface of stainless steel and makes drilling progressively more difficult. The 135° split point on this set assists with clean, accurate starts without a centre punch on most grades of stainless.

Q: What materials are not suitable for this set?

 A: The HSS Cobalt Jobber Drill Bit Set 1-10mm is not designed for masonry, concrete, or tile, which require tungsten carbide-tipped or diamond-core tooling. It is also not recommended for hardened tool steel above approximately HRC 50, where specialist solid carbide tooling is needed. For softwood and sheet timber, a dedicated wood bit produces a cleaner entry and exit without the risk of tear-out.

Q: Can these bits be resharpened once the edge wears?

A: Yes. M35 cobalt bits can be resharpened using a dedicated drill bit sharpener set up for HSS. Cobalt bits are harder than standard HSS but also slightly more brittle, so avoid overheating the tip during sharpening. A correctly resharpened bit will recover close to its original cutting performance, which makes a cobalt set a longer-term investment than standard HSS, particularly for tradespeople who drill hard metals regularly.

Q: What drill speed should I use for different materials?

 A: As a general guide, harder materials and larger diameters require lower speeds. For stainless steel at 6mm diameter, 600 to 800 RPM is a reasonable starting point. For mild steel at the same size, 1,500 to 2,000 RPM is typical. Aluminium and non-ferrous metals tolerate higher speeds than steel. Start slower than you think you need to and increase until the bit cuts cleanly with minimal heat. Always use cutting lubricant on ferrous metals.

Q: Is a 10-piece set with 1mm increments better than a 19-piece set with 0.5mm steps?

 A: It depends on the type of work. A 19-piece set covering 1mm to 10mm in 0.5mm increments is better suited to precision engineering and fabrication where specific tap drill sizes or close-tolerance clearance holes are needed. The 10-piece set with 1mm increments is a more practical site and van kit, covering the most commonly used metric sizes without carrying surplus bits. For general construction, maintenance, and installation work, the 10-piece format handles the vast majority of fixing and clearance hole requirements without unnecessary complexity.

Q: Why should I buy the HSS Cobalt Jobber Drill Bit Set 1-10mm from CMT Group?

A: CMT Group has supplied construction and industrial sites across the UK since 2010, operating a fleet of over 100 FORS Silver-accredited vehicles covering 90% of the country. Orders placed online by 7pm are dispatched for next working day delivery, and a VIP dedicated vehicle service is available UK-wide for time-critical requirements. Trade account holders access agreed contract pricing through the EDGE procurement portal, which integrates directly with existing purchasing systems and provides full visibility of orders, invoices, and proof of deliveries. For teams managing site spend across multiple projects, EDGE eliminates manual data entry and keeps purchasing under full control.