Bosch Titanium Nitride Coated Metal Drill Bit Set

Why these bits earned a spot in my metal kit

A good set of drill bits earns its keep the first time you need a clean, round hole in steel without burning up a tip. After several weeks using the Bosch TiN set across mild steel, aluminum, and a small run in stainless, I’ve come away with a clear picture of where these bits shine, where they don’t, and which configuration makes the most sense depending on the work you do.

What you’re getting

Bosch offers this set in three configurations: 14-, 21-, and 29-piece kits. All are high-speed steel bits coated in titanium nitride (TiN), the familiar gold finish that’s designed to reduce friction and help the cutting edge run cooler and wear longer than uncoated HSS.

• Size coverage:
  • 14-piece (TI14): a practical spread from 1/16 in. through 1/2 in., including two 1/8 in. bits.
  • 21-piece (TI21A): adds more in-between sizes and multiple duplicates of common diameters.
  • 29-piece (TI29): a full index covering 1/16 in. to 1/2 in. in 1/64 in. steps.

The wide coverage is the main draw. If you build toward precise fits—tapping holes, matching hardware, or reaming—having the 29-piece set with every 64th increment is genuinely useful. If you tend to burn through the same small sizes, the 21-piece package’s duplicates save time on job days when you don’t want to stop and resharpen. The 14-piece is a compact, do-most-things kit that still includes a 1/2 in. bit, which is a thoughtful inclusion if you’re stepping up holes with a handheld drill.

TiN coating in practice

TiN is not magic, but it does matter. In my tests, these bits:
- Started more smoothly and with less squeal than plain HSS when run at the same feed and speed.
- Needed less downforce to maintain a chip in mild steel once the cutting lips were engaged.
- Ran noticeably cooler on larger diameters when I used cutting oil and a slower RPM.

If you’re used to black-oxide jobber bits, you’ll feel the difference on the first pass in steel. The coating’s biggest advantage shows up in reduced friction and slightly longer life, especially in the sizes that typically glaze first (1/8 in., 3/16 in., and 1/4 in.). As always, the coating isn’t a free pass to push speeds; get the RPM right and the TiN will help the bit stay sharp longer.

One important note: if you sharpen these bits, you’ll remove the coating at the cutting edge. After that, the edge behaves like plain HSS. You still retain some TiN benefits along the flutes (chip flow and a bit of heat resistance), but don’t expect a freshly sharpened tip to perform like a new TiN-coated edge.

Performance on common materials

I ran the Bosch TiN bits through a handful of real tasks: drilling brackets in 1/8 in. mild steel angle, boring larger holes in 3/16 in. plate, countersinking fasteners in 6061 aluminum, and a short run in 304 stainless to test the limits. Here’s how it went.

• Mild steel (A36)

  • 1/8 in., 3/16 in., and 3/8 in. holes with cutting oil and a center punch started clean, with crisp, continuous chips.
  • At appropriate speeds (think slower as diameter grows), heat stayed under control. Edges on the most-used sizes still felt sharp after a few dozen holes.
  • The 1/2 in. bit is usable in mild steel with a handheld drill if you step up gradually (e.g., 3/16 → 5/16 → 3/8 → 1/2) and keep the RPM low. Expect torque—brace the drill.

• Aluminum (6061)

  • Dry drilling was fine for smaller sizes; a little lubricant prevented chip welding on larger diameters and left a very smooth bore.
  • Chips evacuated well with pecking. Hole walls were bright, and the bits didn’t grab.

• Stainless (304)

  • Small sizes (up to about 1/4 in.) are doable with proper technique: low RPM, firm feed, and cutting fluid. For runs beyond a handful of holes or diameters above 1/4 in., I’d switch to cobalt bits.
  • The TiN coating helped, but there’s no substitute for the right substrate steel in tougher alloys.

• Wood and plastics

  • These bits produce clean holes, but TiN is overkill for soft materials. It’s fine to use them; just don’t expect the coating to change much compared with standard HSS.

I’ll add that these bits aren’t marketed as anti-walk or self-centering tips, so a quick center punch remains the best way to keep holes exactly where you want them, especially on curved or painted stock.

Speed, feed, and technique tips

You’ll get the most from TiN-coated bits with a few habits:

• Match speed to diameter. As the bit gets larger, slow down. For mild steel, think fast for 1/8 in. and below, moderate for 3/16–1/4 in., and slow for 3/8 in. and up.
• Use cutting oil on metals. A drop or two goes a long way on heat management and edge life.
• Center punch to reduce walking. Especially important on metal tubing and round stock.
• Peck on deeper holes. Brief retractions break chips and clear flutes, preventing heat build-up.
• Step up for large holes. Don’t jump from 1/8 in. to 1/2 in. in one go with a handheld drill.
• Clamp your work. Cleaner holes and safer hands.

Follow those basics and the Bosch TiN bits reward you with consistent, round holes and a longer life than plain HSS.

Durability and upkeep

After routine use in mild steel and aluminum, the smaller bits retained their edges well. The gold finish at the cutting lips polished slightly, which is normal. I did touch up a 3/16 in. bit after an aggressive stainless pass; once sharpened, it cut fine but, as expected, lost the TiN advantage right at the edge. That’s the trade-off with any coated HSS: great out of the box, and still serviceable after sharpening, just without the coating’s edge benefit.

If you routinely chew through 1/8 in. and 3/16 in. sizes, the 21-piece set’s duplicates are worth it. For fabrication and repair shops that want to hit odd clearances or tap-drill sizes precisely, the 29-piece set is the keeper—it simply saves time.

Limitations to keep in mind

• Stainless and hardened steels: Small stainless work is fine with care, but for frequent stainless or any hardened steel, cobalt or carbide is the better choice.
• Resharpening reduces the coating benefit: Still perfectly usable, but no longer a “TiN edge.”
• Not a specialty point: You’ll still want to center punch for precise starts.

None of these are surprises; they’re simply the reality of TiN-coated HSS in general-purpose drilling.

Which set to choose

• TI14 (14-piece): Good everyday range, compact kit, includes 1/2 in. for stepped enlargements. Ideal for DIYers and jobsite generalists who don’t need every 64th increment.
• TI21A (21-piece): Smart pick if you burn through common sizes. The duplicates cut downtime and keep you moving.
• TI29 (29-piece): The most versatile. If you fit hardware, tap holes, or aim for press fits, the full index pays for itself in accuracy and convenience.

Pros and cons

Pros:
- TiN coating runs cooler and lasts longer than plain HSS when used correctly.
- Thoughtful size coverage; full 1/64 in. increments available in the 29-piece.
- Duplicates in the 21-piece address real-world breakage and wear.

Cons:
- Not the best choice for frequent stainless or hardened steels.
- Sharpening removes the TiN advantage at the edge.
- Requires proper technique (speed, oil, punch) to realize benefits—no shortcut around fundamentals.

Recommendation

I recommend the Bosch TiN bits as a reliable, general-purpose metal drilling set for anyone who works primarily in mild steel and aluminum, with occasional stainless. The coating delivers the practical benefits it promises—smoother starts, less heat, and longer edge life—provided you match speed to size and use cutting oil on metal. Pick the 29-piece if precision sizing matters to your work, the 21-piece if you value duplicates of the most-used diameters, or the 14-piece if you want a compact kit that still covers the basics up to 1/2 in. For heavy stainless runs or hardened alloys, look toward cobalt or carbide, but as an everyday metal set, these TiN-coated bits are a dependable addition to the toolbox.