How To Use a Core Drill

Do you have a project that requires a core drill but have never used one before? Before getting started, it's important to understand the ins and outs of using a core drill to ensure the job is done right. 

To help you get to grips with using a core drill, this guide will set out everything you need to know, including the different types of core drills and how to use a core drill like a professional.

What is a Core Drill?

Core drills, also known as Annular Cutters or Broach Cutters, make it easier to drill holes in thick metal slabs. This type of drill is best suited to holes larger than 1/2".  

When drilling thick holes in metal or aluminum, you should opt for a core drill rather than a standard twist drill, as these can be tough to operate. 

Core drills are similar to wood hole saws, as they only cut the outer edge of a hole. They cut a groove around the outside of the hole, leaving a solid core or slug in the middle of it. A burr-free, close tolerance hole can be drilled without any pre-drilling or step drilling. 

Core drills are typically used with mag drills, but they can also be employed on machine tools like mills and huge drill presses with tool holders. 

For example, when using a mag drill attached to a large piece of steel for construction work, this type of mechanical cutter can be used to create large diameter holes.

Parts of a Core Drill Or Annular Cutter 

  • Shank - is the end of the drill bit that fits into the drill and is secured by the chuck. It also has a hole on top for the pilot.  
  • Pilot - is a large nail-like device that must be used when utilizing a core drill. Allows for the coolant flow to enter the hole and helps locate the centre of the hole.
  • Flats - make the drill bit more stable.
  • Flutes - used to eject chips from the drill bit during drilling.
  • Cutting edge - does the actual cutting and Comes in different angles known as geometry.

Core Drilling Process

Core drills are great for drilling large holes quickly and efficiently. When using a core drill, you must wear protective equipment before drilling, such as:

  • Safety goggles
  • Drill gloves
  • Thick and protective clothing
  • Dust mask

Once you are fully protected, you can then start the drilling process. To ensure high-quality holes while extending the life of both the drill bit and the machine as a whole, you should follow these important steps:

  1. The first thing you need to do is select the appropriate ejector pin based on the cutter blade's length. Insert the ejector pin into the core drill while grasping it. Never attempt to operate a core drill without inserting an ejector pin first.
  2. Once the ejector pin is in place, you should Insert the core drill bit into the machine's keyless harbor and mark the area where you want to drill the hole.
  3. The next step involves moving the machine near the mark and positioning the tip of the pilot pin over it. Then, activate the magnet switch and verify that the magnet indicator is lit in green.
  4. After the indicator is highlighted, you should adjust the rotating speed of the machine, making sure it is suitable for the size of the cutter. 
  5. Next, switch on the coolant tank switch and the motor switch.  
  6. If possible, use an internal lubricant, especially when drilling through materials with a thickness larger than 50 millimetres. Never operate equipment without first adding lubricant. Apply a generous amount of oil during drilling for best results.
  7. Once you have added lubricant, you should then begin to drill with a constant speed that is not too slow or too fast to prevent damaging the cutter. Drill with less pressure and a steady feed rate for the best results and longer service life. Avoid putting excessive pressure on the feed handle, as this will not result in faster drilling but may cause cutter breakage and accidents.
  8. Make sure to clean the work area after drilling correctly. Metal chards can cut and even cause eye damage, so you have to be careful.

Types of Core Drill 

When using a core drill, it is vital to select an appropriate model for the material you are working with. To help you choose the right one, here are some of the most common core drills available:

High-Speed Steel (HSS) & Cobalt

Most HSS core drills are made from M2 steel. To drill harder materials, cobalt will be added to steel to make M42-type HSS core drills. HSS can withstand higher temperatures. it can be re-sharpened if it becomes dull

TiN and TiAlN Coated

The TiN or titanium coating helps core drill bits to drill harder materials faster. As a result, they outlast standard HSS core drills. The Coating can also help extend tool life by preventing corrosion.

Tungsten Carbide Tipped (TCT) 

Tungsten carbide has very high wear resistance, and its thermal expansion is less than steel. Due to the TCT cutting edge, the annular cutter can drill hard materials with high-quality performance. Tungsten carbide is sharper than most materials and twice harder than steel. It also has hot hardness at high temperatures allowing faster drilling speed.

Cubic Boron Nitride

Ground Cubic Boron Nitride is almost as hard as diamond. The CBN treated annular cutter has sharp flutes and cutting edges. CBN is frequently used for grinding cutting tools due to its excellent thermal and chemical stability.

Standard Vs Stack-Cut Geometry

Most core drills or annular cutters have Standard-Cut geometry, which means they can cut through one piece of steel at a time. However, when the job involves drilling two or more pieces of material, cutters with Stack-Cut geometry must be used. They tend to have a round cylinder shape, as the cutting teeth are cut from the inside out.

Stack geometry core drills have a unique tooth profile that ensures layer-by-layer safety and stability of penetrating capabilities. As a result, the transitions between layers are smooth, and the hole finishes are exact and clean.

What Drill Bits Are Best for Core Drilling?

Wondering which drill bits you should choose when core drilling? 

Drill bits with carbide cores are the best and can be used in a wide range of materials. However, It's best to employ them only when working with hard or abrasive materials, as they're more expensive than other types of bit material. 

Compared to HSS cutters, carbide drill bits require a substantially greater RPM for optimal performance. However, TiAlN-coated core drills are best in horizontal drilling and other applications where lubrication or coolant is not viable due to environmental concerns.

A standard HSS bit can also be utilized in most cases. It is unnecessary to use a coated or carbide cutter on softer metals. However, a coated or carbide bit will pay off in enhanced tool life when working with hard materials.

Compared to standard large drill bits, core drill bits are easier and more efficient to use. Depending on your needs, you can purchase a single drill bit or an entire set. You can find the best core drills for your application by checking out our online store

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