--- title: How to Design Your Own Threading Die for CNC Metalworking siteUrl: https://logzly.com/threadingdies author: threadingdies (Threading Die Workshop) date: 2026-06-15T20:34:35.274079 tags: [threadingdies, metalworking, diy] url: https://logzly.com/threadingdies/how-to-design-your-own-threading-die-for-cnc-metalworking --- **Disclosure: We are reader supported, and earn affiliate commissions when you buy through us.** If you’ve ever stared at a cheap off‑the‑shelf die and thought “that won’t hold up to my project,” you’re not alone. A well‑made die can be the difference between a clean, [strong thread](https://www.amazon.com/s?k=strong+thread&tag=organizationtip101-20) and a ragged mess that makes you want to pull your hair out. In this post I’ll walk you through the whole process, from sketch to finished tool, so you can [make a die that fits your CNC machine](/threadingdies/step-by-step-guide-to-designing-and-cutting-a-custom-threading-die-for-cnc-metalworking) and your exact needs. ## Why a Custom Die Makes Sense Most hobbyists start with a generic die set, but those are made for a wide range of materials and tolerances. When you’re cutting [stainless steel](https://www.amazon.com/s?k=stainless+steel&tag=organizationtip101-20), aluminum, or even a little brass for a [DIY project](https://www.amazon.com/s?k=DIY+project&tag=organizationtip101-20), the standard geometry often leaves you with a loose fit or a stripped thread. A custom die lets you: * Choose the exact thread pitch and profile you need. * Match the material hardness to the workpiece, reducing wear. * Keep the die size compact enough for tight CNC [tool holders](https://www.amazon.com/s?k=tool+holders&tag=organizationtip101-20). A good example of this approach is how you can [build a precision threading die with household items](/threadingdies/build-your-own-precision-threading-die-with-household-items). I learned this the hard way on a 2022 project where I tried to tap a 1/4‑20 hole in a piece of 6061 aluminum using a stock die. The result was a stripped thread and a dented die. After that, I decided to design my own, and the difference was night and day. ## Step 1 – Gather the Specs Before you open any [CAD software](https://www.amazon.com/s?k=CAD+software&tag=organizationtip101-20), write down the basic numbers: * **Thread size** – e.g., M8×1.25 or 1/4‑20. * **Material** – what you’ll be cutting (steel, aluminum, brass). * **Die material** – high‑speed steel (HSS) for most metals, carbide if you need extra life. * **CNC tool holder size** – usually 6 mm or 1/4‑inch shank. Having these details on a [sticky note](https://www.amazon.com/s?k=sticky+note&tag=organizationtip101-20) keeps the design focused and avoids endless back‑and‑forth later. ## Step 2 – Sketch the Profile A threading die is basically a ring with a series of V‑shaped cuts around its circumference. The geometry of those cuts follows the thread profile you’re making. For metric threads, the standard angle is 60°, while UNC/UNF uses 60° as well but with a different pitch. Grab a piece of [graph paper](https://www.amazon.com/s?k=graph+paper&tag=organizationtip101-20) and draw a single tooth: 1. Draw a horizontal line for the die’s outer diameter (OD). 2. Mark the pitch – the distance from one tooth to the next. 3. Using a protractor, draw two lines at half the thread angle (30°) that meet at the bottom of the pitch space. This little triangle is the shape that will cut the thread. Keep the tip radius small – about 0.1 mm for fine threads – because a blunt tip will crush the material instead of cutting it. ## Step 3 – Choose the CAD Tool I use Fusion 360 for most of my designs because it’s free for hobbyists and has a solid “thread” feature. If you prefer SolidWorks or Onshape, the steps are similar. 1. **Create a new sketch** on the XY plane. 2. **Draw a circle** for the die’s inner diameter (ID). This is the hole that will sit over the workpiece. 3. **Draw a second circle** for the outer diameter (OD). Typical OD for a small die is about 30 mm, but size it to fit your CNC collet. 4. **Use the “Thread” command** – set the size, pitch, and class (fit). Turn off the “Modelled thread” option; we only need the profile for cutting. 5. **Extract the profile**: Convert the thread shape into a 2‑D sketch that you can revolve. ## Step 4 – Add the Cutting Teeth Now we turn the 2‑D thread profile into the actual teeth. 1. **Create a new sketch** on the side of the die body. 2. **Project the thread profile** onto this plane. 3. **Offset the profile** outward by the desired tooth depth – usually 0.5 mm for HSS. 4. **Trim the sketch** so you have a single tooth shape. 5. **Pattern the tooth** around the die’s circumference. Use a circular pattern with the number of instances equal to the thread pitch divided into the die’s circumference. For example, an M8×1.25 die with a 30 mm OD will have about 75 teeth (30 mm ÷ (π × 1.25 mm) ≈ 7.6 teeth per revolution, round to a whole number that matches the pitch). Make sure the teeth are evenly spaced; any overlap will cause chatter in the CNC. ## Step 5 – Add Clearance and Shank The die needs a little clearance between the cutting teeth and the workpiece to allow chip flow. Add a small fillet (0.2 mm) at the base of each tooth. Then, draw a shank that matches your CNC holder – a simple cylinder of 6 mm diameter and 20 mm length works for most hobby machines. ## Step 6 – Export and Prepare for Machining Export the model as an STL file. If you have a CNC mill capable of 3‑axis work, you can machine the die from a solid block of HSS. For many hobbyists, a 3‑axis mill with a small end mill (0.5 mm) is enough. **Toolpath tips:** * Use a **roughing pass** with a 2 mm cutter to remove most of the material. * Switch to a **finishing pass** with a 0.5 mm ball‑nose cutter for the teeth. * Keep the spindle speed high (10 000–15 000 rpm) and feed rate low (50–80 mm/min) to avoid tool breakage. * Coolant is a must – a mist of oil works fine for HSS. If you don’t have a mill that can handle HSS, consider buying a small block of carbide and having a professional shop do the final cutting. The cost is still lower than buying a high‑quality die set. ## Step 7 – Test and Refine Once the die is out of the machine, give it a quick visual check. Look for any burrs on the teeth – a light deburr with a fine file will do. Then, mount it in your CNC collet and try a test thread on a scrap piece of the same material you’ll be using. Measure the thread with a caliper or a thread gauge. If the pitch is off by more than a few microns, go back to the CAD file and adjust the tooth spacing. Small tweaks are normal; the first version is rarely perfect. ## Step 8 – Keep a Log I keep a [simple spreadsheet](https://www.amazon.com/s?k=simple+spreadsheet&tag=organizationtip101-20) in my Threading Die Workshop blog’s “lab notes” section. I record: * Material of die (HSS, carbide) * Workpiece material * Spindle speed and feed * Measured results (pitch, depth) Over time this data helps me predict how long a die will last and what settings work best for each material. It’s a habit that saves a lot of trial‑and‑error later. ## Final Thoughts Designing [your own threading die](/threadingdies/how-to-design-your-own-threading-die-for-cnc-metalworking) may sound like a [big project](https://www.amazon.com/s?k=big+project&tag=organizationtip101-20), but break it into these bite‑size steps and you’ll have a tool that fits your CNC perfectly and lasts for years. The satisfaction of watching a clean, crisp thread being cut by a die you designed yourself is worth every minute spent in the CAD program. Give it a try on your next metalworking project – you’ll be amazed at how much control you gain over the final product.