We broke down the most common questions we get asked about Annular Cutter sizes
What is an annular cutter?
An annular cutter is a specialized bit for drilling through steel. Like a hole saw for wood, they only cut the outside edge of a hole. It produces an accurate burr-free reamed like hole. It can drill a much larger hole and requires less force and time than a standard twist drill bit. As it turns, the cutter produces chips from the outside cutting edges and after cutting the hole which leaves a chunk of steel from the center of the cutter then falls out.
What do they look like?
On top of the cutter there is a hole for the pilot pin which is used to locate the center of the cut. Next, there are Flats on the sides which hold the cutter in place in the magnetic drill. The shank which is either ¾ or 1-1/4 diameter which slides into the magnetic drill. On the cutting edge there are flutes that pull the chips out of the hole when cutting. And last the cutting teeth, which have different angles called Geometry that makes the cut.
They cut faster, last longer, produce a better hole finish, and a true round hole with very tight tolerances, can be re-sharpened. They leave a burr free reamed like hole, they are 3 times faster than a twist drill, and require no step drilling. Because they do not have to drill/cut through the complete work piece, they require less thrust and thus less energy to drill through material. Lastly, they have efficient cooling system built in that allows cutting fluid to flow through the center of the bit. Internal lubrication makes these cutters faster and more efficient for deep hole drilling.
The cutter you select depends on the diameter of the hole, the depth of cut and the type of material. There are a wide range designed to cut through the following materials: Carbon Steel, Stainless Steel, Hard Alloys ex: Titanium and aluminum. The most common cutter is high speed steel, and is the standard with most cutters. Some other types are more specialized like cobalt are effective when drilling material with inconsistent composition. Carbide tipped cutters are used for hard or abrasive materials. Titanium Nitride Cutters or TINI have coatings that improve tool life by increasing surface hardness of the tool and providing greater lubricity. TINI coated are generally used in applications where the material being cut is difficult to machine, or when extended tool life is desired.
Depth and Diameter
When determining cutter size, they are measured by depth and diameter. If you look at an actual cutter the depth is actually longer than what it is rated, (a 1" cutter is really 1-1/4") because this ensures the tool can drill all the way through the hole and allows extra length for resharpening. Cutters either come with a ¾” or 1-1/4 weldon shank depending if you’re using Magentic drill or drill press. Some cutters require special arbors to fit properly.
Standard vs. ID or Stack-Cut Geometry
Most annular cutters come with Standard geometry. They are designed to cut through one piece of steel and offer the fastest, and cleanest hole. When the job requires drilling two or more pieces of steel plate, cutters with stack-cut geometry must be used. This special cutting geometry enables two or more steel layers to be drilled in a single operation. The cutting geometry causes the core to be cut from the inside to the outside. This produces a cylindrical core without a protruding burr at the lower end.
A Pilot pin is a large nail looking object that helps start the hole when using an annular cutter. It serves three very important functions it locates the center of the hole. Allows coolant to flow down around the slug and to the cutting teeth and ejects the slug at the end of the cut. Pilot pins tend to last a very long time and can be used with multiple sizes of cutters.
Extending Cutter Life
Coolant and cutting paste increases tool life dramatically. Cutting fluid is a water-based fluid designed to protect galvanized, steel, aluminum, brass and other alloys, it extends tool life, improves surface finish and reduces heat buildup. Drilling upside down can cause fluid to leak from your magnetic drill. Instead use cutting paste that is applied to the inside and cutter teeth to reduce heat buildup and extend the life of the cutter
Re-sharpening your high-speed bits makes them like brand new. You can sharpen your cutters up to 6 times as the cutter are reground on the same CNC machines the cutters were manufactured on to ensure they are true to size and just as sharp as day one.
Most Popular Sizes
Different applications call for different sizes, the most popular diameter sizes are 7/16”, 1/2”, 9/16”, 5/8”, 11/16”, 3/4”, 13/16”, 7/8”, 15/16” and 1”, that have 1” and 2” depth of cut.
There are many brands that make these cutters, some are imported, and some are made in the USA and prices vary, each manufacturer sells different sizes and sets, some include the pilot pins and some do not. Brands, like Jancy, Fein, Evolution, Steelmax, Hougen, Unitec and Milwaukee are just some of the companies that make great hole cutters.