How to Enlarge an Existing Hole in Metal?

If you do metalwork for your project, you may need to enlarge or align a hole in a metal pipe. Most of the time, a reamer is used to do this job. It doesn’t cut hole in metal but enlarges the size of an existing hole. A professional metalworker must know how to widen a drilled hole in metal with the reamer.

In this article, we will try to describe how to enlarge an existing hole in metal with the step-by-step technical guide. You can also get to know how to make a hole in metal by reading this article. Keep reading; you will find this article helpful for your project. I hope this article will make your work easier and fulfill your demand for knowledge regarding this topic.

Related: How to Fix Exhaust Pipe without Welding?

Table of Contents

  • When a Hole Is Reamed In Metal to Size It Is
  • Tool for Enlarging Holes
  • Drilling Hole in Metal (Step By Step Guide)
  • Technical Tips

When a Hole Is Reamed In Metal to Size It Is

When a hole is reamed in metal to size, it expands the hole size and generates a precise size hole. This process of enlarging holes is called reaming.

Reaming is an essential process to enlarge your metal device’s hole so that you don’t have to rethink your chosen process. It will allow you to create a circular hole of your required diameter. You have to make a hole at first with the drill machine and then precise it with a reamer according to your needed diameter. It is a finishing process of the existing hole with a high degree of accuracy. This is instructional content on how to make a hole bigger in metal.

Tool for Enlarging Holes


The Unibit is an excellent tool for drilling holes and to enlarge a hole. It is ideal for soft materials such as plywood, acrylic, etc., and thin materials such as sheet material and stainless steel. You can make a hole of different diameters by step drill bits with a stairstep profile. The larger the bit size is, the more it can enlarge a hole.


Holesaw can cut holes and enlarge the hole size in metal, plastic, wood, and more. It includes a sharped blade to make a large hole in the material, suitable for professional and practical design. But it isn’t easy to expand an existing hole because hole saws depend on a pilot bit to guide them.

Knockout punch

An electrician uses knockout punch generally to enlarge hole size or to create. This tool is mainly used in metal electrical boxes for widening hole size. Knockout punch is a simple hand tool that can enlarge a hole in sheet metal.

According to mechanical engineers, there are different types of reamer based on function, such as hand reamer, jobbers reamer, shell reamer, chucking straight fluted reamers, taper pin reamer, etc. All of them are rotary cutting tools to enlarge the diameter of a previously formed hole. Reamer is readied with two or more peripheral trenches or flutes made of high carbon steel. 

Drilling Hole in Metal (Step By Step Guide)

Here we will describe how to drill hole in metal with the step-by-step guide.

Step-1: Securely Fix the Workpiece

First of all, fix the workpiece securely so that it can’t move from the workplace.

Step-2: Choose Appropriate Reamer

Then choose an appropriate reamer according to your required hole size. You have to choose your reamer according to what material you will reame, needed diameter, desired accuracy, finishing, etc. You have to select your reaming tool very carefully that has impacted a lot to get the right size hole. Almost any size reamer is available to the industrial supplier with thousands of inch and hundreds of millimeter increments. So, performing reaming correctly, this step is essential.

Step-3: Fit the Reamer to the Drive Tool

Then equip the reamer to the driver tool properly.

Step-4: Choose Correct Adapter

When you have to use a Holemaker Technology reamer in a socket wrench power tool, magnetic drilling machine, or SDS drilling machine, choosing the appropriate adapter is essential. Then fit the adapter to the drive equipment and inject the reamer. After that, fit the reamer into the drill and tighten the screw properly.

Step-5: Insert Reamer into the Hole

Insert reamer into the hole to widen it. While setting the reamer with a magnet drill into the hole, make sure to turn off the magnet drill for the reamer’s correct moving.

Step-6: Start the Cut

Now start the cut. Apply pressure steadily. Making the speed of the reamer half will be good and make the feed double. Reach the reamer to the hole as deep as the hole size is needed. When the cut is complete, stop the reamer and withdraw it.

Technical Tips

Drill your hole at an angle you are going to ream because the reamer follows the drill hole.

  • Never run a reamer in reverse
  • Try to use cutting oil while working
  • Research before choosing a reamer size to get the required hole diameter.
  • Be aware of your safety first. Put on protective gloves and safety goggles
  • If you need to ream a blind hole, drill a little deeper with pilot drills.

Final Words

Reaming is a process that can make your job easier when you need to enlarge a hole size. It makes an existing hole bigger than it already is. It is mainly used for the circular hole but to cut square hole in metal. You need a square broach tool instead of the reamer. How much stock leave depends on the reamer’s size, so you need to focus on stock allowance while working. There are plenty of tools with different types to widen a hole size. You have to choose the right way for you. In this article, I tried to describe how to make a hole in metal in a few words to understand it easily.

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