Different tool engineering, composition, and design affect the way they perform and which workpieces they will cut most effectively. Several factors determine which drill bits work best on various steels and alloys, copper, zinc, aluminum, tin, etc., owing to the properties of ferrous vs. nonferrous metals.

Ferrous Metals

Ferrous metals, of course, are those that contain iron. These include stainless, carbon, and alloy steel, and cast and wrought iron. Ferrous metals generally possess more tensile strength than their non-iron-based counterparts. That makes them ideal for use in building materials, structural and ornamental designs, and heavy industrial products such as shipping containers, tools, and appliances. Tool manufacturers must consider hardness and strength when designing and engineering drills made for cutting ferrous metals.

Non-ferrous Metals

Non-ferrous metals - especially copper, lead, zinc, and tin also occupy important niches in the construction and manufacturing industries. Because they contain no iron, these metals are valued for their use in applications where they come into contact with moisture that would rust ferrous metals. They also are malleable, ductile, and easily manipulated into various shapes for components, housings, etc.  They are non-magnetic, making them quite useful in electronic components.
 
Hardness is the primary consideration when choosing a drill to cut metal.

​Drills incorporate various design elements in order to cope with these different challenges

Drill bit points can be altered to provide more precise hole-starting, centering, and quality, as well as conduciveness to varying feeds and speeds. The standard 118-degree point is used because it offers a “good enough” fit for most applications.

​Standard points can be used for most “softer” steels and non-ferrous metals. Standard 135-degree split-point drills can cut these materials, as well as harder steel alloys. In these harder materials, the split-point offers the advantage of working at lower feed pressure and centering of the hole with minimal walking. Learn more about how to find the right drill point angle for your application

As we might expect, the harder the material being drilled, the harder the tool must be to get the job done. Carbon steels are too soft for cutting metal; only high-speed steel (HSS), carbide-tipped, and solid carbide bits should be used in cutting metal, no matter how soft. HSS is common because of its low cost and ability to drill softer carbon steels as well as zinc, copper, aluminum, and other non-ferrous metals.

Alloying HSS with 5 to 8% cobalt adds  “red” hardness which allows the tool to maintain the sharp cutting edge longer and allows for slightly faster speeds, making these drills suitable for working in heat-treated steel, cast iron, and even some titanium alloys.

For exponential increases in speed and wear resistance, nothing beats using a carbide tool. It withstands extremely high temperatures, resists wear, and maintains rigidity better that HSS. It costs much more, but is the only long term, high volume option when the work piece is stainless steel or alloyed steel. Carbide-tipped HSS saves some costs and is a viable option for nonferrous metals such as copper, bronze, and other materials that are highly abrasive.
 
Drills made of cobalt-alloy High Speed Steel (HSS-E) or even drill bits with a thin film coating are needed for stainless steel. These are more expensive than normal HSS drill bits, but they enable drilling in special steel without a high level of drill bit wear.

Thin film coated drill bits are high-speed steel drill bits (HSS) that have any of a variety of coating blends typically with a titanium base. TiN (Titanium Nitride), TiALN (Titanium Aluminum Nitride) and TiCN (Titanium Carbonitride) are examples of thin film coaing typically used on drill bits. They are very hard, and corrosion-resistant and reduce the co-efficient of friction allowing for better lubrication of the tool. They last much longer than regular HSS drill bits, and they are good for cutting through any metal, including metal sheeting.

Thin film coated drill bits have a surface that is harder than cobalt. However, because they are coated, they lose the coating protection at the cutting edge when they are re-sharpened and subsequent tool life will be reduced. Uncoated drill bits are made of cobalt or HSS steel, and they can be sharpened without any loss in ​performance or tool life.

Understanding the characteristics of ferrous and non-ferrous metals, and what twist drill is ideal for each material is key to high quality production and extending tool life. If you are still unsure of exactly which drill is right for your job, contact a Browne & Co. Sales Rep and we would be happy to assist you.

If you deal with exotic alloys like Inconel, titanium, Hastelloy, etc., this article is written especially for you. Wise operators always select the correct tool for the job, avoiding the problems others face when they try to apply a general-purpose tool to a unique situation. In this article, we give you the information you need to select the proper tools for machining exotics. It will make your shop stand out from the competition since you will produce better results at a reduced cost.

The Hard Stuff
Exotic alloys are specifically designed for high-temperature applications (think aerospace), performance in corrosive environments (think underground), or to have the highest available strength to weight ratios (think earth-moving applications). The machinability of these materials is NOT the first consideration. As much as it would be nice from the machinist’s viewpoint to have an aluminum firewall in a helicopter, as the pilot or passenger you want a material that is strong and heat retardant.
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The Answer
One day a new job order comes in and you are faced with threading these kinds of alloys. What’s an operator to do? Fortunately for you, North American Tool manufactures application-specific thread mills right here in the USA.

These tools are made from solid carbide and have been specially designed with exotic materials in mind. The results are longer more consistent tool life and the elimination of scrap due to tap failures in your parts.

Uniquely Crafted
North American Tool thread mills for exotic alloys are designed with only three teeth. This places less stress on the tool than a conventional thread mill with six, eight, or ten teeth engaged in the workpiece at the same time. Carbide thread mills nickel-based alloys are also made with left-hand helix and left hand-cut, which permit an operator to run from the top of the hole to the bottom and climb mill the threads.

​This will create a right-hand thread on the part. The threads are milled, rather than cut, typically producing a better quality thread in the part.

The thread mills are coated with AlCrN to give them greater heat and wear resistance in the high heat, higher abrasive applications that typically confront an operator when machining exotic alloys.

Exotic Material Experts
As well as thread mills, we are the industry leader in designing and manufacturing special taps for exotic materials as well. Thread mills are a good alternative tool to the special taps we design every day provided of course, you have a 3-axis CNC capable of the interpolation tool path needed for thread mills.


If you are working with exotic materials and need a thread mill or special tap, please contact us for a quote. We’d be happy to help.