Bosch 3-5/8" T-Shank jig saw blades (basic for metal)

Why I tested these blades

Thin sheet metal rewards the right blade; the wrong one chatters, overheats, and leaves a ragged mess. I put Bosch’s T118A blades—let’s just call them the Bosch thin‑metal jigsaw blades—through a mix of shop and site tasks to see how they hold up in real work. My pack was marked “Made in Switzerland,” and each blade is a 3-5/8 in T‑shank, high‑speed steel (HSS) with wavy-set, milled teeth and a progressive 17–24 TPI pitch, aimed squarely at 1–3 mm material.

Build and tooth design

A few things stood out right away:

• The wavy-set, milled teeth are uniform and sharp out of the pack. That wave set is what you want for thin sheet—it keeps multiple teeth engaged and spreads the cutting load, which reduces snagging.
• Progressive pitch (finer near the tip, slightly coarser along the body) helps with gentle starts and slightly faster clearing once the cut is established.
• HSS is fully hardened. It’s keen and heat tolerant up to a point, but less forgiving than bimetal if you flex the blade or drive it hot. These are designed for straight cuts and controlled feed—not for tight curves or hacking through brackets.

The T‑shank fit was secure in Bosch and Makita saws I tested. No wobble, positive lock-in, and easy changes.

Test setup and saw settings

• Jigsaws: Bosch barrel‑grip and a Bosch top‑handle with variable speed and orbital action.
• Orbital action: Off for all metal cuts.
• Stroke rate: Typically 2–3 on the Bosch dial (roughly low‑to‑mid speed). Higher speeds were reserved for aluminum with lubrication.
• Lubrication: A few drops of cutting oil or wax stick on steel; WD‑40 on aluminum.
• Workholding: Rigidly clamped sheet with a sacrificial backer to reduce vibration and burrs; straightedge guide for long cuts.

Those details matter. These blades will punish rushed feed or dry cutting, especially in steel.

Performance: aluminum, mild steel, and stainless

• 1 mm aluminum sheet: Fast, clean, and drama-free. With light lubrication and a mid stroke rate, the blade tracked well and threw fine chips. Edge quality was surprisingly good for a jigsaw—light deburring with a file was all that was needed. I could cut gentle radii, but I still treated these as straight‑cut blades and avoided tight curves.

• 1.2–1.6 mm (18–16 ga) mild steel: This is the sweet spot. With orbital off, slow feed, and a dab of oil, cuts were steady and predictable. Heat management was the difference between a blade that lasts and one that fades early. By keeping speed moderate and pausing to let the blade cool on long rips, I maintained sharpness for multiple cuts. Burrs were present (that’s typical for jigsaw cuts in steel), but they were small and consistent.

• 3 mm mild steel: At the upper end of the blade’s rating, it’s possible, but patience is mandatory. Short, straight cuts are fine; longer runs become a test of technique. I kept the saw slow, leaned on lubrication, and used a fence to prevent wandering. The blade stayed intact and finished the cuts, but I could feel it losing bite by the end of a long rip. This is where a shear, nibbler, or an abrasive solution often makes more sense.

• Thin stainless (approx. 1 mm): Doable for short sections with excellent cooling and very slow feed, but the HSS teeth dull faster than they would on mild steel. For stainless or long runs, a bimetal blade tends to outlast HSS.

Cut quality and tracking

These blades are honest about their lane: straight cuts in thin sheet. With a fence or guide, line tracking was excellent, and the short length helps reduce deflection. If I tried to force tight curves, I could feel resistance and hear that “teeth skating” sound that tells you you’re stressing the set.

On galvanized sheet, the finish was respectable; on plain mild steel, I saw fine burrs along the exit edge. A quick pass with a deburring tool or flap wheel cleaned it up. Chip evacuation is good for a fine‑tooth metal blade; the wave set and milled profile help keep the gullets from clogging.

Speed, heat, and blade life

The common failure mode for HSS in sheet metal is heat dulling. Run them too fast, push too hard, and they fade quickly. Use the right approach, and they last far longer than their price would suggest. My real‑world results:

• 1 mm aluminum: Multiple long cuts per blade without noticeable dulling when lubricated. Minimal heat buildup.
• 1.2–1.6 mm steel: Consistent performance over several feet of cutting if I stayed disciplined on speed and lubrication. Dry cutting at high speed shortened life dramatically.
• 3 mm steel: Usable but taxing; expect one blade per long cut if you drive it continuously. Pausing and cooling helps.

If you routinely need to plow through long steel cuts, a bimetal jigsaw blade or a different tool category will serve you better. For occasional fabrication, panel openings, and in‑situ trim, these blades earn their keep.

Compatibility and handling

• T‑shank fits most modern jigsaws without adapters.
• The short length lets the blade stay stiff and track straight, but it limits your ability to contour. That’s a fair trade‑off for sheet metal work.
• The 3‑5/8 in length also keeps reciprocating mass low, which reduces chatter in thin stock.

Where they shine and where they don’t

They shine when:
- Cutting aluminum and mild steel sheet in the 1–3 mm range
- Straight cuts guided by a fence or track
- Situations where a shear or nibbler won’t reach and you need clean, controlled cuts with a handheld tool
- Shop settings where you can clamp securely and manage speed and cooling

They struggle when:
- Pushed hard, run dry, or used at high stroke rates in steel
- Cutting stainless or thicker material for long distances
- Attempting tight curves or aggressive scroll work in metal
- Used as a one‑blade solution for heavy fabrication

Tips to get the best out of these blades

• Turn orbital action off for all metal.
• Start with a pilot hole rather than a plunge start; it preserves the fine tip teeth.
• Use cutting oil or wax, especially on steel. Reapply on long cuts.
• Keep stroke rate modest and feed gently. Let the teeth do the work.
• Support the work on a backer board and clamp both sides of the cut to tame vibration.
• Use a straightedge guide for long rips; it improves speed and blade life.
• Deburr the edge immediately; the chips are sharp and hot—gloves and eye protection are not optional.

Value

You get five blades per pack, and the cost per cut is good if you use them within their intended window. I’d still keep a few bimetal blades on hand for stainless and long steel runs, but for thin sheet in the typical shop or jobsite scenario, these HSS blades are efficient and economical. Fit and finish are excellent, and in my hands, the performance matched the specs on the sleeve.

Final take

The Bosch thin‑metal jigsaw blades do exactly what they claim: straight, controlled cuts in thin sheet metal with a fine finish, provided you respect speed, lubrication, and material limits. They’re not a universal metal‑cutting solution, and they’re not meant to be. Used properly, they cut cleanly and track well; abused, they dull fast—just like most HSS sheet‑metal blades.

Recommendation: I recommend these for anyone who needs reliable straight cuts in 1–3 mm aluminum or mild steel using a T‑shank jigsaw. They reward good technique with clean edges and reasonable blade life. If your work leans toward stainless, heavier gauges, or long production runs, reach for bimetal jigsaw blades or a different tool, but keep a pack of these in your kit for the thin‑sheet tasks they handle so well.