Frequently Asked Questions

A Midget Mill is a ground rotary file (also called a rotary bur) invented by Severance Tool Industries in 1931. Unlike stamped or machined rotary files, Midget Mills are precision-ground from solid bar stock, producing more uniform teeth, better concentricity, and a smoother cutting action.

They are used in die grinders and rotary tools for deburring, grinding, porting, weld blending, and shaping metals. Available in HSS (M2 High Speed Steel, Rc 63–65) and Carbide, in shapes A through Z, with 1/4-inch shanks.

The name "Midget Mill" comes from their small size compared to full-size milling cutters. Despite the name, they are serious industrial cutting tools used in shops worldwide.

EDP stands for Electronic Data Processing. An EDP number is a unique numeric identifier assigned to each specific tool configuration — combining size, shape, material, and cut style into a single ordering code.

For example, a 1/4"-diameter Shape A HSS Midget Mill has a different EDP number than a 1/4" Shape A Carbide Midget Mill, even though they look similar. EDP numbers are used by distributors and purchasing departments for accurate ordering and inventory management.

You can search by EDP number using the search bar at the top of any page on this website.

Severance tools are manufactured in Saginaw, Michigan, USA. The company has been operating from its Saginaw facility since 1939 and continues to manufacture all products domestically.

Severance Tool Industries is a proud American manufacturer with over 90 years of cutting tool expertise. Every Midget Mill, countersink, and specialty tool is made in-house, from raw material to finished product.

Severance tools are sold through a network of authorized industrial distributors throughout the United States and Canada. These distributors stock the most popular items and can order any tool from the catalog.

To find a distributor near you:

• Call us at 989-777-5500
• Use our contact form
• Email us with your location and the products you need

For large or custom orders, you can also contact our sales team directly.

HSS (High Speed Steel) tools are tougher, less expensive, and more forgiving of impact. They work well on soft-to-medium materials and are ideal for general-purpose work and low volumes.

Carbide (Tungsten Carbide) tools are much harder, run at double the speed, and last 10–20 times longer. They cost 3–5 times more but deliver lower cost per part in production. Required for hardened materials over Rc 45.

For a complete comparison with cost analysis and application recommendations, see our detailed guide:

Here are the most popular shapes and their applications:

• Shape A (Cylindrical) — The most versatile shape. Use for flat surfaces, straight walls, slots, and general deburring. If you only have one shape, make it an A.
• Shape C (Ball) — For concave surfaces, internal radii, die cavities, and rounding internal corners.
• Shape N (Inverted Cone) — For back-side deburring. Reach through a hole to deburr the far side.
• Shape D (Ball Nose Cylinder) — For slots and channels with rounded bottoms.
• Shape G (Tree Pointed) — For V-grooves, narrow slots, and tight tapered areas.
• Shape W (Flame) — For elongated cavities and narrow access areas.

• 82° — US standard flat-head screws. This is the most common angle in American manufacturing.
• 90° — Metric/ISO flat-head screws. Standard for metric fasteners worldwide.
• 100° — Aerospace AN/MS fasteners. Required for aircraft structural work.
• 60° — Center holes (lathe centers), deburring, and spotting.
• 120° — Shallow chamfering and deburring large holes.

When in doubt in a US shop, 82° is the safest default.

A Chatterless Countersink is Severance's proprietary countersink design featuring 6 flutes with unequal spacing.

Conventional countersinks have evenly-spaced flutes that can vibrate at a harmonic frequency, creating chatter — a rough, wavy finish with loud squealing. This is especially common in drill presses and hand-held tools.

The unequal flute spacing of the Chatterless design breaks up these harmonics, producing a smooth, clean countersink even in setups that lack the rigidity of a CNC machine. This means better results with less effort, regardless of your equipment.

Available in all standard angles: 60°, 82°, 90°, 100°, 110°, and 120°.

Both are rotary files with 1/4" shanks, but they differ in cut pattern and material:

• Midget Mills: Available in HSS or Carbide with a single-cut (one set of flutes) pattern. Provide good finish and controlled stock removal. The most versatile product line.
• Carbo-Mills: Carbide-only with a double-cut (cross-hatch) pattern. Cut more aggressively, remove stock faster, and produce a finer finish than single-cut because the cross-hatched teeth create smaller chips.

Choose Midget Mills for general-purpose work, finishing, and when you need HSS. Choose Carbo-Mills when you need faster stock removal in production environments and want a finer finish from carbide.

Calculate using the formula: RPM = SFM × 3.82 ÷ Tool Diameter (inches)

Recommended surface speeds:

• HSS rotary files: 150–300 SFM
• Carbide rotary files: 300–600 SFM

Example: A 1/4" HSS Midget Mill at 200 SFM: 200 × 3.82 ÷ 0.250 = 3,056 RPM.

Adjust based on workpiece material — run slower on stainless steel and titanium, faster on aluminum and brass. Always start at the lower end and increase gradually.

Yes. Severance offers a professional regrind service that restores worn tools to original factory geometry and cutting performance.

• HSS tools: Reground on standard aluminum oxide wheels. Easy and cost-effective.
• Carbide tools: Require diamond grinding wheels. More specialized but still much cheaper than buying new.

Most tools can be reground 2–4 times, saving 40–60% compared to purchasing new. The reground tools perform like new when done by our experienced technicians on purpose-built equipment.

Severance rotary files are available in three standard shank sizes:

• 1/4" shank — Midget Mills, Carbo-Mills, and Sever-Cuts. Fits standard die grinders, right-angle grinders, and most industrial air tools. This is the most common size.
• 1/8" shank — Junior Mills. Fits pencil grinders, Dremel-type tools, and small pneumatic grinders. Ideal for detail work in tight spaces.
• 3/32" shank — Lab Mills. Fits precision rotary handpieces used in dental, jewelry, and laboratory applications. The smallest form factor.

Countersinks are available with various shank configurations including straight shank and hex shank, depending on the product line.

Yes. Severance Tool Industries manufactures custom rotary files, countersinks, and specialty cutting tools to customer specifications. Custom options include:

• Non-standard diameters
• Special flute lengths
• Custom shank sizes
• Modified shapes
• Special materials or coatings
• Combination tools

Contact our engineering team to discuss your requirements. We will work with you to design a tool optimized for your specific application. Minimum order quantities may apply for custom tooling.

Severance tools can cut virtually any machinable material. Here are the most common:

• Mild steel (1018, 1045, A36) — HSS or Carbide
• Tool steel (D2, H13, A2) — Carbide recommended, required if hardened
• Stainless steel (304, 316, 17-4) — Carbide recommended, use cutting fluid
• Aluminum (6061, 7075, cast) — Use Sever-Cuts to prevent loading
• Cast iron — Carbide strongly recommended (very abrasive)
• Brass and bronze — HSS or Carbide, light pressure
• Copper — Use wax stick to prevent loading
• Titanium — Carbide required, use flood coolant
• Plastics (Nylon, Delrin, ABS) — Light pressure, avoid heat buildup
• Composites / Fiberglass — Carbide required (extremely abrasive)

For hardened steels above Rc 45, carbide is required — HSS will not cut effectively.

Carbide tools typically last 10 to 20 times longer than equivalent HSS tools when cutting the same material at appropriate speeds.

The actual ratio depends on the workpiece material:

• Abrasive materials (cast iron, fiberglass, composites): Carbide may last 20× or more compared to HSS.
• Hardened steel (above Rc 45): HSS cannot effectively cut these materials at all, so carbide is not just longer-lasting — it is the only option.
• Softer materials (aluminum, brass, mild steel): The ratio may be closer to 10×, since HSS performs well here.

Despite costing 3–5 times more upfront, carbide tools deliver a significantly lower cost per part in production applications due to fewer tool changes, less downtime, and more consistent performance across the tool's life.