Threading Got You Tied Up? Here’s a Smarter Way – Carmex Spiral Mill-Thread®

by Bernard Martin

If you’re still tapping threads the old-school way or burning hours on single-point threading, you might be missing a serious opportunity to improve your process. The Carmex Spiral Mill-Thread® system is purpose-built for shops running CNCs that want cleaner threads, faster cycles, and less tool replacement headache.
This isn’t just a “fancier tap”—it’s a complete, indexable thread milling system that brings versatility and efficiency together in a way that's hard to beat.

5 Reasons Why More Shops Are Making the Switch to Spiral Mill-Thread

1. You don’t throw out the whole tool when it wears down.  This system uses indexable inserts, so all the cutting happens at the insert—not the holder. When the edge is done, just change the insert and keep cutting. No need to re-zero or pull the holder out of the machine. It’s fast, simple, and keeps your spindle turning.
2. It cuts threads the smart way. Instead of forcing a tap through the hole in one shot, Spiral Mill-Thread uses helical interpolation. That means it mills the thread profile gradually, which puts less stress on your machine and your tooling. You get better surface finishes and eliminate the risk of broken taps, especially in blind holes.
3. One insert can cover multiple sizes. As long as you’re sticking with the same thread pitch, a single insert can handle different diameters—internal or external. So instead of stocking up on a dozen different taps, you just need one insert and a few holders to handle most jobs.
4. It’s faster—especially on large threads. With 2.5 to 3 threads being cut per insert, you’re knocking out full threads in fewer passes. That can easily cut your cycle times in half compared to single-point threading or tapping, especially on bigger parts.
5. Coolant-through holders keep chips under control. Most of the toolholders are designed with through-coolant, so you’re getting lubrication right where it’s needed. That’s a big deal when you’re threading deep holes or working with tough materials like stainless or titanium. It helps with chip evacuation, tool life, and finish.

Toolholder Options That Fit How You Run
Carmex  didn’t build this system with just one kind of job in mind. Whether you’re doing short reach, deep bores, or large OD threads, there’s a holder for it:

• SIR/SLR Series – Standard right- and left-hand holders
• SIR-L/SLR-L Series – Long-reach versions when you’re down in a bore
• SIM/SLM Shell Mill Holders – Great for large external threads (think API or big hydraulics)

Inserts That Last

• Grade MT7 – Tough sub-micron carbide with a high-performance PVD coating. It’ll handle steel, stainless, and nickel alloys no problem.
• MXC Coating – Even tougher. Best when you’re pushing hard or dealing with nasty materials.

Threads You Can Cut
You’re not stuck with just standard UN or ISO here. Carmex ​ offers inserts for:

• UN / UNJ
• ISO Metric
• NPT / NPTF
• BSPP / BSPT
• API
• Trapezoidal (DIN 103)
• Specials (just ask)

Who's Using It?

• Job shops love it for cutting down setup and tooling costs.
• Aerospace guys rely on it when they can’t afford a bad thread in titanium.
• Medical manufacturers use it to hit high-tolerance internal threads without tapping.
• Hydraulic shops dig it for pipe threads and deep ports where taps struggle.

Whether you’re running 10 parts or 10,000, this system scales up or down without making your life more complicated.

Where It Really Shines
Shops doing aerospace, energy, medical, hydraulic fittings, or anything with high thread tolerance are seeing major benefits. But even general job shops are loving this because it cuts time, reduces broken tools, and makes threading a lot more predictable.

You can thread a small bore in 316 stainless without sweating, or knock out large threads in API connections using the same family of tools. Once you dial in your helical interpolation program, you’re off to the races.

Bottom Line?
If you’re dealing with broken taps, long thread cycles, or just too much clutter in your tooling drawer, the Carmex ​ Spiral Mill-Thread® system is worth a serious look. You’ll spend less time changing tools, cut better threads, and keep your machine running steady.
Need help figuring out which holder and insert combo fits your machine? Let’s talk. We’ll get you set up with a system that works for your parts, your material, and your cycle times.

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