Bosch 40 pc. Metric Tap and Die Set

Why I reached for this set

Thread repair and light fabrication come up in my shop more often than I expect—fixing a nicked bolt on a motorcycle brake lever, adding threads to a mild-steel standoff, or cleaning up a stubborn hole in an aluminum bracket. For that blend of repair and small-scale making, the Bosch metric tap and die set has been a steady, predictable option. It’s a 40‑piece collection aimed squarely at right‑hand metric work, built from heat‑treated high‑carbon steel with a rust‑ and tarnish‑resistant finish and laser‑etched sizes. Nothing flashy, but the basics are done well.

Build and materials

The first impression is the steel: heat‑treated high‑carbon. That’s the right choice for general purpose tapping and threading in mild steels, aluminum, brass, and plastics. It doesn’t have the edge retention of high‑speed steel (HSS) in hard alloys, but it’s tougher than the bargain‑bin carbon steel sets that chatter and crumble under load. The finish has held up; I’ve been liberal with cutting oil and careless with cleanup on hectic days, and the tools haven’t shown spotting or film rust. Laser‑etched markings are a tangible quality-of-life improvement—stamped sizes fill with grime, while these remain legible after a wipe with a rag.

The taps arrive sharp, with a clean grind on the flutes. The dies have a neat, uniform bore with no burrs. None of the pieces arrived out of round, and I didn’t find machining burrs that sometimes plague value‑tier kits. That consistency matters when you’re trying to start a die square on a rod without hunting for the thread.

Scope and sizing

This set covers common right‑hand metric sizes. That’s a strength and a limitation. If you mostly work with M6/M8/M10 fasteners and the usual fine/coarse thread pitches for small shop projects, you’re covered. If you need left‑hand threads, oddball pitches, or extensive coverage beyond the common range, you’ll be reaching for another kit. For my automotive, bicycle, and general shop projects, the coverage hits the sweet spot.

Setup and use

Tapping is all about alignment, lubrication, and patience. With those boxes checked, this set produces clean, predictable results. My typical workflow:

• Drill the correct pilot hole for the thread size, deburr and add a small chamfer.
• Apply cutting fluid generously.
• Start the tap by hand, making sure it’s square in both axes.
• Advance a quarter to half turn, back off an eighth to break chips, repeat.

Using that approach, the taps cut smoothly in aluminum and brass with minimal torque. In mild steel, I feel steady resistance but no grit or squeal—just that controlled, buttery feedback you hope for. The lead on the tap noses is ground well enough that starting a hole by hand is straightforward; you don’t fight for a thread to bite.

On the die side, I’ve cut new threads on mild‑steel rod stock and chased dinged threads on bolts that picked up damage from vice jaws. The dies track straight when you start square. With oil and modest pressure, chips curl and clear from the flutes without packing. The threads they produce fit standard nuts with even engagement and no tight spots. After cleanup, I rarely need more than a light deburr to get a fastener to spin freely.

Performance across materials

• Aluminum: Fast, clean tapping with excellent surface finish on the thread flanks. Easy to over‑zealously drive; the taps are sharp, so I keep the back‑off cadence frequent to avoid long chips.
• Brass: Nearly effortless. Threads come out crisp and full‑height with a bright finish. Great for small instrument repairs.
• Mild steel: The real test for a set like this. With cutting oil and a steady cadence, the taps and dies produce accurate, repeatable threads and hold their edge across multiple holes. Chip control is fine; I haven’t had to force anything or rescue broken taps.
• Plastics: Works, but I go slowly and avoid heat buildup. A tapered starter tap prevents tearing in brittle plastics.
• Stainless: This is where I set limits. I tested a short pass on 304 and didn’t push it. The taps cut but required more torque, and I could feel the edge working harder than I’d like for long‑term tool life. For stainless or hard alloys, I switch to HSS or cobalt tooling.

Accuracy and fit

The thread form from both taps and dies is consistent. Gauging by feel and test fits, the resulting threads engage smoothly and maintain proper pitch without the “tight at the start, loose at the end” symptom that shows up with off‑center dies. On common sizes I use—think typical metric fasteners in shop projects—nuts spin on by hand and torque down without galling. That’s as much as I ask from a general‑purpose set.

Durability and maintenance

After multiple weekends of use, the cutting edges remain sharp enough that I don’t have to add pressure to compensate for wear. The finish resists rust as advertised; even after a few lazy cleanups, I haven’t found orange blooms or tarnish. That said, I still treat any threading tools the same way:

• Use cutting fluid appropriate to the material.
• Clear chips frequently.
• Avoid lateral loading and binding.
• Clean, dry, and oil lightly before storage.

Follow that routine, and high‑carbon steel like this holds up well in a hobby or light‑professional environment.

What I’d change

No set is perfect. A few practical limitations showed up:

• Metric and right‑hand only. If you switch between metric and imperial, or need left‑hand threads, you’ll need additional sets.
• High‑carbon steel, not HSS. For stainless, hardened steels, or production work, I’d want HSS or cobalt taps/dies with coatings to manage heat and wear.
• Coverage stops at “common sizes.” If your work demands a wide range of fine pitches or larger diameters, this won’t be a one‑stop solution.

None of these are deal‑breakers for what this set aims to do, but they’re worth considering based on your workload.

Who it’s for

• General shop users who need reliable metric threading without diving into exotic materials.
• Automotive, motorcycle, and bicycle tinkers repairing or chasing threads on brackets, housings, and hardware.
• Makers and fabricators working in aluminum and mild steel for fixtures, prototypes, and small assemblies.
• Maintenance techs who want a go‑to for cleaning up damaged fasteners.

If your day job is building stainless process equipment or you regularly cut long runs in alloy steels, step up to HSS. If you’re squarely in the repair and light‑fabrication camp, this kit fits nicely.

Value

This set sits in a sensible spot: better made and more consistent than bargain kits that dull quickly or snap under load, but without the premium cost of full HSS assortments. The materials, finish, and legible markings add up to fewer annoyances on the bench, and that’s often where real value shows up. I judge threading tools by whether I hesitate before grabbing them; with this set, I don’t.

Practical tips for better results

• Chamfer the hole or rod end before threading. It helps the tap or die start square and reduces burrs.
• Match pilot drill sizes to the thread chart; being off by even half a millimeter can ruin thread quality.
• Keep alignment honest. A small machinist’s square or tapping guide pays for itself.
• Use proper cutting fluid and don’t rush. The forward‑then‑back step is boring but effective.
• Deburr and clean threads after cutting, then test with a nut/bolt before installation.

Recommendation

I recommend the Bosch metric tap and die set for anyone who needs dependable, right‑hand metric threading in aluminum, brass, plastics, and mild steel. It’s well‑made for the category, with sharp cutting edges, corrosion‑resistant finish, and markings you can actually read after a long day. The set’s main limitations—metric only, right‑hand only, and high‑carbon steel instead of HSS—are clear and reasonable for its intended use. If your work frequently involves stainless or hardened materials, you’ll be better served by an HSS kit. For general shop tasks, repair work, and light fabrication, this set is exactly the kind of reliable, no‑drama tool that earns a permanent spot within reach.