Sheet metal must have holes drilled or punched into it for a wide variety of purposes, the majority of which involve either mounting components or routing wiring and other materials. There isn’t always a right or incorrect method to complete the job, just like there isn’t always a right or wrong way to complete any other normal fabrication activity.
However, there is often a more effective approach. In this lecture, we will go through a variety of techniques for drilling and punching holes in sheet metal. Some of these methods are interchangeable with one another, but this is contingent on the application that requires the hole to be made for, the size of the hole, and the costs associated with the necessary tooling.
Step One: Being Prepared Is Crucial
Finding the centers of all the holes you need to make should always be the first step you take in any project like this. After that, if you want to outline the boundaries of the hole, you can use a compass or a circular template, although this step is completely optional.
After the hole centers have been designated with ink or crosshairs scribed on the material, use a center punch to make a hole in each area. The dimples that are left behind by the center punch are used as guides for the drill bits and punch tips, preventing them from walking or otherwise straying across the surface of the sheet metal.
Although automatic and spring-loaded center punches are speedy and convenient to operate, the versatility offered by a set of manual punches in conjunction with a ball-peen hammer is superior.
Step 2: Make Certain to Always Make Use of a Clamp, or Three
Drilling a sheet-metal workpiece requires that you never, ever handle it in your hands, and you should always clamp it down whenever you can. When installing clamps or hold-downs, you should plan for the possibility that a drill bit will snag and seize the workpiece. In this case, you should adjust your clamps so that the metal cannot spin. What do you get when you put human flesh in contact with whirling sheet metal? A miserable day, if you’re fortunate; a trip to the emergency room, if you aren’t.
Before you clamp down your workpiece, you might want to consider covering the back of the sheet with tape. This will assist you in better control and prevent tear-out. Masking is not required in this scenario in which the sheet is going to be attached to a sacrificial wooden board for the same reason. Even if the surface of your workpiece is already finished or is readily damaged, you should still consider masking both the front and the back of it just in case.
Step 3: Twist Drills are an Excellent Choice for Making Holes of a Narrow Diameter
Using a twist drill to make a hole in a sheet of metal is a procedure that may be completed with relative ease. You begin by drilling a pilot hole with a relatively modest diameter, and then you continue to drill holes of progressively bigger diameters until you reach the required size. This approach is effective for creating holes of a modest diameter; nevertheless, it can be laborious and time-consuming when the job requires creating a big number of holes, a large number of holes, or both.
Cutting fluids can be utilized with twist drills, however, they are typically unnecessary when working with thinner gauge sheet metal due to the drills’ higher cutting speeds. When you need to drill through heavier sheets of metal or steel, you should probably keep a bottle on hand just in case.
Step 4: Skipping Some Steps with the Help of a Step Drill Bit
Step drill bits, such as the time-honored Unbait, have the capability of simultaneously drilling holes of varying diameters. These single-flute bits have been developed specifically for use with thin materials, and they have steps that gradually increase in diameter from one to the next.
Self-starting step bits don’t need any pilot holes to be bored before they can generate big burr-free holes in the blink of an eye. This eliminates the time-consuming step of drilling the holes beforehand. Even larger holes (usually 1-3/8 inches diameter or less) can be made in sheet metal using step bits, however, these bits require that pilot holes be drilled first. It is usual to to to to to practice using a self-starting step bit to make the big pilot hole required for a hole-enlarging step bit. This is because self-starting step bits are designed to start themselves.
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Hole Saws for Large Openings, the Fifth Step
Hole saws function differently than twist and step drill bits in that they remove material from the opening’s perimeter rather than drilling it. Metal-cutting hole saws normally come in sizes ranging from 3/4 inches up to 6 inches, and they have a sawtooth-tipped cylinder with a pilot drill bit located at the very center of the saw. Some hole saws include arbors and pilot bits that are secured in place permanently, while others are modular and need to be built.
A backer board is not only useful for minimizing tear-out, but it also assists in guiding the pilot bit of a hole saw, which helps to keep the device in the correct position. Cutting fluid is a useful tool that, when used with larger saws and stronger materials (like steel), can make the cutting process more efficient and extend the life of the saw. In most cases, the manufacturer will give a table that details the appropriate hole sizes and cutting speeds in terms of revolutions per minute (rpm).
Hole saws, just like regular drill bits, have the potential to bind, and when they do, they exert a great deal of power on the material they are cutting through. If you are using a handheld drill on a piece of work that is securely secured, you should arrange your grip and body in such a way that you won’t get hit by the drill if it grabs the workpiece and yanks it out of your hands.
Portable hand punches that don’t make a mess and have enough agenda grip are the sixth step.
It is possible to utilize a hand punch, such as those manufactured by Roper Whitney, to create precise holes in sheet metal in a short amount of time and with a minimal amount of work. Bench-mounted punches that are more sturdy and more expensive may be required for creating larger holes or when working with thicker gauges of steel.
Before using a portable hand punch, it is necessary to first pick and install a punch and die set that is compatible with the punch. After positioning the punch such that its point is centered above the future hole’s center, push the tool’s handles together to create the hole. After the punch has passed completely through the sheet, a little slug will fall loose, and you will then be able to remove the tool. Holes that have been punched have edges that are relatively clean and require very little to no polishing.
The seventh step is to knock out your opponent with sheer force.
The holes that can be made by knockout punches, such as Greenlee’s famous Slug-Buster, are significantly larger than the ones that can be made by a portable hand punch. Knockout punches are simple to operate and produce excellent results, but unfortunately, greater sizes are prohibitively expensive. These punches are typically used by electricians to punch holes in conduits.
The draw stud, the punch, and the die are the three components that make up a knockout punch. To prepare the punch for use, begin by using a step drill bit to create a pilot hole in a piece of sheet metal. Before putting the draw stud through the pilot hole, position the die so that it is on top of the stud.
After that, the punch is threaded onto the end of the draw stud, and it is moved near the sheet metal. The draw stud is then turned with a socket or a wrench, which progressively draws the punch through the sheet metal and into the die. After the punch has been dragged entirely through the stud, the hole will be finished and the punch will be able to be removed from the stud.
Deburring is often necessary for holes created by knocking them out, although not to the same extent as for holes created by hole saws.
Circle Cutters for Large or Unevenly Sized Holes is Step 8 of the Process
It’s possible that you need to drill a hole with an unusual or atypically sized diameter. In this particular scenario, you will want to make a circle cut out of the material rather than punch a hole in it.
Sheet metal can be drilled or punched to create holes, and in both cases, the hole is more or less completely removed in one motion. To make a hole in the middle of a circle when cutting it out, one or sometimes two cutting tools are rotated about a central point.
The circle cutter that you see before you was manufactured by General Tools. It is intended to be utilized in conjunction with a drill press. To operate it, you need to adjust the distance between the pilot bit and the cutter so that it matches the diameter of the hole you want to make. Because this circular cutter is not perfectly well balanced, using it can make it unsteady and can be potentially hazardous.
Circle-cutter attachments for rotary tools in the form of Dremel and RotoZip are also available, making it possible to cut big holes without using a drill press.
Step 9: Obtaining a Silky Surface
Even while it is possible to cut some holes in sheet metal extremely precisely, most of them will need some light finishing to provide the best results. This step can be bypassed if the application calls for grommets or rubber trim to be installed in or over the holes. If such an application exists, however, this step is not required.
There are a few different approaches to cleaning and deburring a hole that has just been drilled or punched. When dealing with holes of a smaller diameter, it is typically sufficient to simply break down any sharp edges by giving a slightly larger-sized twist drill a light finger twist over the hole. Using a portable deburring tool is the quickest and easiest way to clean up jagged edges when you are smoothing out larger holes that need to be deburred.
To use a deburring tool, place the sharp edge of the tool’s blade against the rim of a hole that has recently been drilled, and then move the blade in a circular motion. As the deburring blade cleans up the area around the hole, it will automatically adjust itself as it eliminates a very thin layer of material.
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