Bosch Impact Tough Titanium Nitride-Coated Drill Bit Set

First impressions

I tossed the Bosch Impact Tough bits into my drill/driver for a week of mixed chores—cabinet hardware in plywood, anchors in drywall, a bracket in aluminum angle, and a quick fix on a steel gate. Out of the box, the titanium nitride (TiN) coating is uniform and the cutting edges look clean. These are straightforward twist bits with an impact‑resistant design; nothing flashy, just meant to survive a bit of jobsite abuse. I ran the 5‑piece TI5IM set for most household tasks and swapped in the 9‑piece TI9IM when I needed the larger sizes.

The range covers essentials. The 5‑piece kit includes 3/32, 1/8, 5/32, 3/16, and 1/4 inch. The 9‑piece adds 1/16, 7/32, 5/16, and 3/8 inch. If your work lives between pilot holes and 3/8 inch through-holes, you’re covered.

Performance in wood and composites

In pine and poplar, the Impact Tough bits do exactly what I want general-purpose bits to do: start predictably and clear chips without drama. With steady pressure, I got clean holes and minimal fuzzing on the exit side. In plywood and MDF, they tracked straight and produced clean edges as long as I backed off near exit to avoid blowout. They’re not brad‑points, so if you’re drilling visible holes in hardwoods, you’ll still prefer brad‑points for ultra‑clean entry. But for fast, accurate utility holes, these performed well.

I ran the 1/8 and 3/16 extensively for hardware and pilot holes. They stayed sharp across a few dozen holes in softwood and sheet goods without noticeable slowdown, which is typical of TiN‑coated bits in those materials. The coating helps reduce friction; you can feel the bit cutting rather than rubbing when you hit the right speed.

Plastics and nonferrous metals

For PVC and acrylic, the bits worked best at moderate drill speed with light pressure to avoid grabbing. The TiN coating helps keep heat down, and I didn’t see melting or chattering when I pecked the hole and cleared chips. If you’re drilling acrylic, masking tape over the entry point and a slower rpm help prevent edge chipping.

Aluminum angle and sheet (1/8 inch and thinner) went smoothly. I used a dab of light oil and a lower rpm, and the bits cut cleanly without overheating. Holes were round and burrs were minimal—nothing a quick deburr couldn’t tidy. The 3/8 inch bit tracked well in aluminum with a center punch and patient feed; chip evacuation was good enough that I didn’t stall or gall the hole.

Mild steel and where the limits show

The real test for general‑purpose TiN bits is steel. In thin mild‑steel strap and light-gauge box tubing, the Impact Tough bits got the job done with the right technique: center punch, slow speed, peck to clear chips, and cutting oil. The smaller sizes (3/32 to 5/32) held their edge through repeated holes without much fuss.

Once I moved into thicker stock and larger diameters, the limitations showed up. The 1/4 and 5/16 bits in 3/16‑inch mild steel needed careful speed control and firm, consistent pressure to maintain bite. When I rushed or let the rpm climb, the edges lost crispness faster than a cobalt bit would. The 3/8 bit managed a few holes in 1/8‑inch steel but dulled noticeably once heat built up. That’s not unusual for TiN‑coated general‑purpose bits; they’re fine for occasional steel, but they’re not the right choice if steel is your main diet, especially thicker stock or anything harder than mild steel.

The takeaway: for sporadic holes in mild steel, these are workable if you slow down and use oil. For regular steel work—or stainless—cobalt or carbide is a better long‑term play.

Impact‑driver use

Bosch calls these “impact‑resistant,” and I did use them with an impact driver via a chuck adapter when speed mattered more than finesse. The bits tolerated the percussive action without chipping or twisting at the shank in my testing, particularly in wood and aluminum. As with any twist bit in an impact driver, control on metal is trickier: the hammering can encourage walking if you don’t punch your start point. I preferred a drill/driver for steel, but it’s good to know these bits won’t instantly protest if you reach for the impact out of convenience.

Durability and heat management

TiN helps with lubrication and wear resistance, which is why these bits feel smooth and stay effective in wood, plastics, and aluminum. Heat management is the real story. In forgiving materials, they stay cool and sharp for a long time. In steel, the cutting edges lose temper if you let heat build—especially in larger diameters. That showed up as slower cutting and shiny cutting lips after a few aggressive holes.

To keep them performing:
- Use a center punch on metal to prevent skating and reduce friction.
- Run at slower rpm for steel; faster for wood and plastics.
- Apply light cutting oil in metal; dry in wood.
- Peck drill to clear chips and allow the bit to cool between passes.
- Step up through sizes rather than jumping straight to 3/8 in steel.

Follow those basics and you’ll get more life out of the set.

Set composition and coverage

Between the TI5IM and TI9IM, you get a pragmatic spread of sizes:
- TI5IM (5‑pc): 3/32, 1/8, 5/32, 3/16, 1/4
- TI9IM (9‑pc): 1/16, 3/32, 1/8, 5/32, 3/16, 7/32, 1/4, 5/16, 3/8

The 9‑piece kit is the more complete option for shop and site work, simply because 5/16 and 3/8 come up often for bolts and pass‑throughs. The 5‑piece is a tidy everyday kit for pilots, small hardware, and anchors. If you regularly need sizes above 3/8 or more incremental steps (11/64, 9/32), you’ll still want a fuller index, but as grab‑and‑go sets these hit the common targets.

Where these bits make sense

• General carpentry and installation: Pilots for screws, hinge hardware, and through‑holes in trim and framing.
• Electrical and HVAC odds and ends: Light-gauge sheet metal, junction boxes, and strut, especially with a punch and oil.
• Shop projects in aluminum: Brackets, extrusions, and sheet where a clean hole at reasonable speed matters.

Where they’re less ideal:
- Frequent drilling in steel thicker than 1/8 inch, especially at larger diameters.
- Stainless, hardened fasteners, or spring steel.
- Fine woodworking joinery where brad‑points or Forstners provide cleaner geometry.

Tips for better results

• Mark and punch your holes in metal; even a small dimple dramatically improves accuracy and bit life.
• Match speed to material: slow for steel, medium for plastics, faster for wood. If you see smoke or discoloration on the cutting lips, you’re going too fast or pushing too hard.
• Use cutting oil on ferrous metals; keep it off wood to avoid staining.
• Step drill: 1/8 to 3/16 to 1/4, rather than forcing a large bit to do all the work.
• Let the bit cut—don’t lean on it. Excess pressure just makes heat.

The bottom line

The Bosch Impact Tough bits are well‑mannered, general‑purpose performers with a coating that pays dividends in wood, plastics, and aluminum. They’re convenient, durable in the materials most DIYers and tradespeople touch daily, and sturdy enough to survive occasional impact‑driver use. In mild steel, they’re serviceable if you use proper technique, but they’re not the right choice for regular or heavy steel work—cobalt or carbide will outlast and out‑perform them there.

Recommendation: I recommend these bits as a dependable, everyday set for wood, plastics, aluminum, and occasional mild steel. Choose the 9‑piece if you want fuller coverage up to 3/8 inch, and pair them with a dedicated cobalt set if steel is a routine part of your work. That combination covers nearly all common drilling tasks without breaking bits—or patience.