How to Read Thread Mill Specifications: Length of Cut, Pitch, Coating & More

If you’ve ever looked at a thread mill product page and felt lost among codes like TM12×1.5×L40-D6, you’re not alone.
Many CNC buyers struggle to read thread mill specifications correctly, which can lead to the wrong tool choice, poor thread quality, or tool breakage.

This guide explains what each parameter means — so you can order the right thread mill for your machining needs.

---

1. Why Thread Mill Specifications Matter

Every detail in a thread mill specification defines how it performs:

• Cutting length determines thread depth capability.

• Pitch defines the thread shape and feed per revolution.

• Coating affects wear resistance and tool life.

• Thread form determines compatibility (Metric, UN, NPT, BSP, etc.).

Understanding these parameters ensures:
✅ better tool matching
✅ fewer setup issues
✅ consistent thread quality
✅ longer tool life

---

2. Common Thread Mill Specification Format

You’ll often see something like this:

Example:
TM-M10×1.5×40L-D6-DLC

Let’s break it down:

Tip: Always check both the pitch and thread form (Metric, UN, BSPT, NPT) when ordering internationally.

---

3. Key Specifications Explained

(1) Length of Cut (LOC)

• Defines how deep the thread mill can cut.

• For example, a LOC of 40mm means it can cut a thread up to 40mm deep in one pass.

• Longer LOC increases flexibility but reduces tool rigidity — so balance is key.

Tip: Choose a LOC slightly longer than your required thread depth.
Avoid overly long LOC — it may cause vibration or breakage.

---

(2) Thread Pitch

• Pitch = the distance between thread peaks.

• In Metric threads, it’s measured in millimeters (e.g., 1.5mm).

• In Inch threads, it’s measured as TPI (threads per inch), e.g., 20 TPI.

Example:

• M10×1.5 → Metric thread, 1.5 mm pitch

• 1/4-20 UNF → Inch thread, 20 TPI

Understanding pitch ensures your threads fit perfectly with mating parts.

---

(3) Thread Form

• Refers to the profile shape of the thread.

• Common types include:

• Metric (M) — ISO standard, 60° angle

• UN (Unified Thread) — common in US industry

• NPT / BSPT — tapered pipe threads

• Whitworth (BSW) — older UK standard

Always confirm the thread form with your customer’s drawing before ordering — mismatched thread forms cause costly rework.

---

(4) Shank Diameter (D)

• The portion of the tool clamped in your collet or holder.

• Standard diameters: 4mm, 6mm, 8mm, 10mm, etc.

• Ensure compatibility with your CNC holder and gauge length.

---

(5) Coating Type

Thread mill coatings are not just cosmetic — they define tool performance.

Pro Tip: For aluminum alloy (e.g. 6061, 7050), always use DLC coating to prevent chip sticking and improve lifespan.

---

4. How to Choose the Right Thread Mill for Your Job

When in doubt, share your thread standard + material type + depth with your supplier — a reliable manufacturer can quickly match the correct model.

---

5. Avoid These Common Mistakes

❌ Choosing the wrong pitch or thread form (Metric vs UN).
❌ Using too long a tool for shallow holes.
❌ Ignoring coating type — especially for aluminum.
❌ Not checking tool holder fit (shank diameter mismatch).

Each of these can cause poor thread quality, vibration, or early tool wear.

---

6. Real Example: Understanding a Product Code

Product Code:
TM-UN 1/2-20×2.0L-D10-TiAlN

Breakdown:

• UN → Unified Thread (inch system)

• 1/2-20 → 1/2" thread, 20 TPI

• 2.0L → 2.0 inch cutting length

• D10 → 10 mm shank diameter

• TiAlN → Heat-resistant coating for steel

This tells the buyer: it’s an inch thread mill, with high-temp coating, suitable for stainless steel or alloy steel machining.

---

7. Summary: Quick Reference Chart

---

8. Conclusion: Read Specs Like a Pro

Once you understand how to read thread mill specifications, you can:
✅ Avoid costly mismatches
✅ Improve machining precision
✅ Extend tool life
✅ Communicate clearly with suppliers

If you often source carbide thread mills internationally, always double-check:

• Thread form (Metric, UN, NPT)

• Material and coating

• Tool diameter and shank fit

---

Need Help Matching Your Thread Mill?

Our factory team specializes in solid carbide thread mills for Metric, UN, and NPT standards — all customizable by pitch, coating, and cutting length.

Download our Thread Mill Size Chart
Request a Free Quotation
Talk to our Engineers for technical recommendations

Get Expert Help Now