Bosch 40 pc. Metric Tap and Die Set

Why this set has stayed on my bench

A dependable tap-and-die set earns its keep the first time it rescues a damaged bolt or lets you add a clean thread where there wasn’t one. After several weeks using the Bosch metric tap-and-die set, I’ve come to appreciate it for what it is: a straightforward, well-made, metric-focused kit that handles most day-to-day threading jobs without fuss. It’s not a premium high-speed steel set for aggressive production work, but it doesn’t try to be. For general cutting and repair on common materials, it’s a solid companion.

Build quality and materials

The components are made from heat-treated carbon steel, and that choice defines the set’s character. Carbon steel taps and dies tend to be a little more forgiving when learning good technique, and they’re perfectly suited to chasing threads and cutting in softer materials like aluminum and mild steel. The tradeoff is longevity and performance in tougher alloys; if you regularly attack stainless or hardened fasteners, you’ll want high-speed steel.

Bosch coats the pieces in a rust- and tarnish-resistant finish and laser-etches the size markings. The finish did its job: after multiple sessions with cutting oil and a week of shop humidity, I saw no spotting or dull gray bloom that some uncoated sets pick up. The laser etching is crisp and high contrast. Even after wiping down oily tools with a rag that’s seen better days, the markings remained easy to read.

What’s inside and how I used it

The set covers a range of common metric sizes with plug taps for internal threads and dies for external threads. Plug taps are the general-purpose option, with a chamfer that starts easily and cuts cleanly through. I paired the taps and dies with my own tap wrench and die stock; the tools seated securely, and the square ends on the taps were consistent, which matters when you want predictable alignment.

For testing, I tapped pilot holes in 6061 aluminum and low-carbon steel flat bar using appropriate drill sizes from my index and a sulfurized cutting oil. I also chased a handful of slightly mushroomed bolts and reconditioned a brake bracket’s threads that had seen one too many impact gun passes.

• Starting the taps: The plug chamfer grabs predictably when you’re square. In aluminum, the first full thread formed within a couple turns with clean, tight chips. In mild steel, I could feel more resistance—as expected—but the taps still cut without chatter. Backing off a quarter turn to break chips was smooth, with that satisfying “click” as chips snapped.

• Cutting with the dies: The dies tracked true once started and didn’t skitter or gouge. On previously abused bolts, they peeled back mashed threads without tearing the underlying base metal, leaving threads that gauged properly and accepted nuts smoothly.

• Finish quality: Threads came out consistent and free of ragged edges. After a quick deburr, fasteners started by hand and seated to torque without the gritty feel you get from rough-cut threads.

Performance limits

To map out the edges, I tried a short cut in 304 stainless on a scrap stud. The die did make progress, and the threads were serviceable, but the effort climbed quickly and heat built up even with cutting fluid. That’s par for the course with carbon steel. If stainless and tool steel are your regular diet, look elsewhere or keep a few HSS taps and dies in your drawer for those jobs.

Another constraint: the set uses plug taps exclusively. They’re versatile, but if you need to thread close to the bottom of a blind hole, you’ll want a matching bottoming tap to finish the last few threads. I handled one blind-hole job by cutting most of the way with a plug tap and then switching to a bottoming tap from my personal stash to complete it. That’s not a knock—plug taps are the right default—but it’s worth planning for.

Durability and edge retention

After tapping multiple holes in aluminum and steel and chasing a dozen or so fasteners, the cutting edges still feel sharp to the fingernail, and chip formation remains clean. I don’t see rolled edges or micro-chipping under a loupe. Carbon steel won’t rival HSS for long-term wear, but with proper technique—don’t force the cut, use lubricant, and clear chips—it holds up well for typical shop tasks.

I’m also encouraged by the finish. Even after a few sessions where I neglected to wipe the dies immediately, a later cleaning and light oiling left them looking fresh. If you’re habitually careless about post-use cleanup, no finish will save you; but if you follow a simple wipe-and-oil routine, this set should resist the slow creep of tarnish.

Markings, organization, and usability

Laser-etched markings are one of those creature comforts you miss immediately when they’re absent. On this set, they’re large enough to read at a glance, and the etching stands up to solvent wipes. Sizing up components mid-job didn’t slow me down, and I wasn’t forced into trial-and-error matching.

The chamfer geometry on both taps and dies feels conservative in a good way—easy to start, with less tendency to cross-thread if you’re careful about alignment. I used a small machinist’s square to confirm perpendicularity on critical holes; the taps tracked straight without steering.

Tips for best results

• Use the right lubricant: I had the smoothest results with sulfurized cutting oil in steel and a lighter cutting fluid in aluminum. Dry cutting not only feels worse but shortens tool life.

• Start square: Even a slight tilt will produce sloppy threads or broken taps. Use a guide block or square, especially on thicker material.

• Break chips: Quarter-turn back after every half-turn forward in steel; a little less aggressive in aluminum.

• Clear and clean: Blow out holes, wipe the tools, and add a film of oil before storage to take advantage of the rust-resistant finish.

• Mind the material: Treat stainless as an exception, not the rule, for this carbon steel set.

Where it shines and where it doesn’t

Strengths:
- Cuts and chases common metric threads cleanly in aluminum and mild steel.
- Heat-treated carbon steel holds an edge well under normal loads.
- Laser-etched markings are legible and durable.
- Rust- and tarnish-resistant finish reduces maintenance anxiety.

Limitations:
- Not ideal for frequent stainless or hardened fasteners.
- Plug taps only; you’ll need bottoming taps for tight blind-hole work.
- Depending on your use case, you may want to add a thread gauge or alignment guide to your kit.

Who should consider it

If you’re a general fabricator, automotive DIYer, appliance tech, or maintenance pro who regularly encounters metric hardware, this set fits the bill for routine thread cutting and repair. It’s especially good for those building out a capable shop on a reasonable budget without jumping straight to high-speed steel. If you routinely build fixtures in stainless, or if your workday is spent tapping 100 holes at a time, you’ll be happier investing in HSS taps and dies and augmenting with specialized geometries.

Final recommendation

I recommend the Bosch metric tap-and-die set for everyday metric threading and repair in aluminum and mild steel. It’s well executed where it matters—sharp, predictable cutting edges; durable, clearly marked components; and a finish that shrugs off shop conditions. Pair it with good technique and a couple of supplemental bottoming taps, and it will handle most of the metric threading tasks that come through a general-purpose shop. If your work leans heavily on stainless or demands production throughput, step up to high-speed steel; otherwise, this set is a reliable, no-drama choice that earns its spot in the drawer.