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Working with Sheet Metal: Safety, Tools, and Sheetmetal Projects

Sheetmetal is one of the most versatile types of metal a do-it-yourselfer (DIY) can use to complete projects that call for bending sheet metal, cutting, or other methods of metal fabrication. This guide will help you understand types of sheet metal, how to safely punch out and cut sheet metal, how to bend sheet metal, and more.

Sheet Metal Safety Precautions

Working with sheet metal, especially after it's been cut, can be dangerous. Each cut you make exposes sharp edges and creates burrs that can slice a finger. That's why it's vital that you take safety precautions. Wear safety gloves whenever possible, and always wear safety goggles and work boots. Never run your hands, even when gloved, over a cut edge. Always file down burrs promptly. Keep your work surface free of scrap. Metal waste also has hazardous edges. Handle metal sheets with care, especially if they are wet, because moisture mixed with oil and dirt can slick the surface and make it hard to grasp. Finally, make sure your hammers are solid and your shears are sharp.

Sheet Metal Types and Sizes

Light sheet metal — metal rolled thin enough to be shaped with hand tools — is one of the most versatile materials for home-improvement projects. It sheathes the roofs and sides of buildings, and it forms gutters and flashing, ductwork, and exhaust hoods. It can be rolled into cylinders, folded into boxes and, depending on the kind of metal, used for objects that are both decorative and practical.

Sheet metals of stainless steel and copper are prized for their luster, aluminum for its light weight and resistance to rust, and galvanized steel — steel with a coating of zinc to forestall rust — for its low cost and easy handling properties. Galvanized steel is the metal of choice for most household projects.

All sheet metals come in a range of thicknesses up to ¼ inch — the point at which sheet metal becomes known as plate. But the measuring systems for thicknesses vary. For stainless and galvanized steel, manufacturers use measurements in decimal parts of an inch or gauge numbers. The gauge is based on the United States Standard system for iron and steel sheet. The lower the gauge number, the greater the thickness.

For aluminum sheet, makers use measurements in decimal parts of an inch to indicate thickness. They generally class copper by weight, in ounces per square foot. For example, flashing on commercial roofing uses 16-ounce (.02 inch thick) copper; decorative items such as exhaust hoods use 24-ounce (.032 inch) copper.

Manufacturers also size nonferrous metals (those with little or no iron content) by gauge numbers. These gauges are based on a second system, known as Brown & Sharpe or American Standard. In this system the precise thickness of each gauge is slightly different from that of gauge numbers of the United States Standard system, a difference to keep in mind when you are buying sheet metal.

For most household projects, like ductwork, containers, and plant boxes, you'll likely use 30 and 28 (.0125 and .0157 of an inch) gauges of galvanized-steel sheet. Metal in these sizes, which you'll likely use most often, is flexible enough to handle easily but rigid enough to ensure a sturdy product. Occasionally you may need a stiffer sheet, 26 gauge, for projects such as a toolbox or an exhaust hood. And if you are replacing a section of duct, you will need to match the gauge of the existing metal. A gauge guide simplifies this measurement.

Whatever the gauge, most sheet metal comes 2 feet to 4 feet wide and 8 feet to 10 feet long. Large sheets are difficult to handle, so your supplier should roll or cut the metal into manageable sections for you to carry it home. To estimate the size of these sections, you need to make a paper or cardboard pattern of the sheet-metal object, unfolded and flattened out. Called a stretch-out, this pattern will also be your cutting guide. It should contain precise measurements for all the critical dimensions of the finished object, plus tabs of extra material for seams and for the rolled and folded hems that blunt the sharp edges of the sheet metal and make them stronger.

When you complete the stretch-out, transfer the pattern to the metal by pricking and scoring it. Then you can cut and bend the metal and fasten it, much as if you were working with paper.

A Gallery of Sheet-Metal Stakes

Sheet-metal workers use iron posts called stakes to support the metal while they work on it. The rounded end of a hollow mandrel stake supports pipes, buckets, and similar articles with curved sides during seaming, grooving, and finishing. The squared anvil at the stake's other end provides a surface for seaming and finishing boxes and rectangular ducts. Use the hatchet stake to make angular folds, such as at the corners of a box. Its sharp edge creases metal crisply. The two horns of different diameters on the conductor stake shape curves and cylinders of various sizes. Shape broad cones and tapered objects on the shorter horn of the blowhorn stake. The slender horn is used for shaping longer and narrower cones.

The shanks of the hatchet, conductor, and blowhorn stakes fit into holes on a steel bench plate, which you can bolt to your workbench. Or you can clamp the stakes in a vise. The hollow mandrel stake attaches directly to your bench with a bolt that slides in a groove on the underside of the tool, allowing varying lengths of the stake to extend over the edge of the bench.

Drafting a Pattern and Transferring to Sheet Metal

Pipes, ducts and containers made of sheet metal can be fully described by a paper pattern. The pattern, often called a stretch-out, has to include all of the seams, folds, and hems that you would need to fold it into the exact shape of the sheet-metal object you want to make. The process of creating a precise and fully detailed pattern is called "drafting."

A Stretch-out for a Rectangular Duct

To draft the stretch-out for a simple rectangular duct of the type that moves air through a heating and cooling system, rule off two parallel lines on a strip of cardboard or stiff paper. Make the distance between the lines equal to the length you desire for the finished duct. Mark off the lines into four panels, alternating in size, making the first and third panels the size of the duct sides, the second and fourth panels the size of the duct top and bottom. Mark the fold lines between panels with Xs. Make a 60° notch about â…?inch deep at each end of the fold lines, and angle the four corners of the stretch-out. For a simple lap seam, add a tab of the desired width at one end of the stretch-out. Cut out the stretch-out and fold it to make sure the duct will be the proper size (inset).

Fashioning a Cylinder

Using a ruler and a steel square, draw a stretch-out equal in length to the circumference of the completed cylinder, allowing an extra ¼ inch for the overlap in a folded seam. To calculate the circumference, multiply the desired diameter by 3.14. Make the width of the stretch-out equal to the length of the completed cylinder. For the folded seam add two¼-inch tabs, one at each end. Mark the fold lines with Xs to distinguish them from the body of the pattern. Cut out the stretch-out and roll it to check its dimensions.

Plotting a Basic Box

To draft a basic box, begin the stretch-out with a rectangle whose dimensions equal those of the bottom of the planned box. Extend the rectangle to form the box sides, making these extensions equal in width to the planned height of the box. Add two tabs for lap seams to the ends of two opposite sides. You'll make four tabs in all. Then add the desired hem allowance to the outer edge of all four sides. Angle the ends of the hem and seam allowances for a neat finish. Mark all the fold lines with Xs. Cut out the pattern and assemble the box to check it for size and shape.

Pricking the Reference Points

To transfer the paper pattern to the workpiece,. position the pattern on the metal sheet to produce as little waste as possible. Secure the pattern with masking tape. Using a ball-peen hammer and a prick punch, mark the metal at each corner of the bottom and sides and at the corners of the hem and seam tabs. At each X that marks a fold line, tap lightly through the pattern to the metal, just barely marking the metal.

Scribing the Outline

Line up the edge of a steel ruler flush with the edge of the pattern and, using a scriber, lightly scratch the outline of the pattern onto the metal. Keep the point of the scriber pressed firmly against the ruler edge so that the outline is true. Then lift the pattern off the metal and set it aside.

Marking the Fold Lines

With the scriber and the steel ruler, retrace the faint outline you have just scratched around the outside of the pattern. Then line up the ruler with the prick marks indicating corners and fold lines. Lightly scribe the fold lines. Be careful not to scribe these lines too deeply, or you may weaken the seams, hems, and corner folds. When all of the lines on the paper pattern are visible on the metal, you are ready to begin cutting.

Cutting Sheet Metal

Cutting sheet metal to the shape and size you need is the intermediate step in fashioning any sheet-metal object — the step between laying out the pattern and bending and fastening the metal into its final form. Because of its relative thinness and flexibility, you can cut sheet metal up to 22-gauge with hand tools almost as effortlessly as you would cut paper with scissors. Use a hacksaw to cut thicker sheet metal, like metal plate.

Aviation snips are the most common tools for cutting both straight and curved lines. A metal punch is another way to cut sheet metal. Both snips and punches require maintenance. You should sharpen them periodically. Keep the joints of your snips well adjusted by tightening the pivot bolt that holds the sides of the tool together. To keep the snips working smoothly, occasionally oil this joint with household oil or a silicone lubricant.

A few power tools work well as sheet-metal cutters. For cutting holes of various sizes, you can use a hand-held electric drill or a drill press fitted with special bits for sheet metal. For cutting large patterns that have either straight or curved lines, you can use a hand-held power shear or a band saw.

Before using a band saw to cut metal, be sure its parts are adjusted correctly. First adjust the blade tension according to the saw manufacturer's instructions. The blade guides, which flank the blade on either side, should be tightened directly against the blade, then loosened until you can slip a piece of paper between each guide and the blade.

Safety Precautions in Working with Sheet Metal

Working with sheet metal, especially after it's been cut, can be dangerous. Each cut you make exposes sharp edges and creates burrs that can slice a finger. That's why it's vital that you take safety precautions. Wear gloves whenever possible, and always wear goggles. Never run your hands, even when gloved, over a cut edge. Always file down burrs promptly. Keep your work surface free of scrap, since metal waste also has hazardous edges. Handle metal sheets with care, especially if they are wet. Moisture mixed with oil and dirt can slick the metal surface and make it hard to grasp. Finally, make sure your hammers are solid and your shears are sharp.

Aviation Shears for Straight Lines and Curves

Cutting a straight line on metal

Select snip grips designed for straight cutting. Set the work on a flat surface, grasp the metal with one hand and insert the metal between the blades at the guideline, pushing the snips forward as far as they will go. Keeping the snip grips perpendicular to the metal surface, squeeze firmly until the blades close to within ¼ inch of their tips. Do not close the blades completely — this would cause burrs and irregularities along the cut edge. Open the blades slowly while applying gentle forward pressure in the direction of the cut, then close them again in the same manner. Repeat this action until you have completed the cut. Push the waste metal away from you in an upward or downward curve to avoid cutting your welding gloves. When the cut is done, file the edge to remove any burrs.

Cutting Along a Broad Curve on Metal

Using snips designed for curve cutting, begin as you do for a straight cut, with the metal held flat and the guideline pushed as far between the snip blades as it will go. Continue the cut, keeping the grips perpendicular to the metal surface, but angle the tool slightly to the right or left to follow the guideline. The blades, because of their shape, will automatically cut along the curve, do not force them. Push waste metal away from you, and file the cut edge to remove burrs.

Snipping a Notch in a Cutout on Metal

Use straight-cut aviation snips to make the notches in a sheet-metal cutout. Hold the blades over the notch guideline, aligning the tips with the point of the notch. Cut, closing the blade tips completely at the corner of the notch.

How to Bend and Fold Sheet Metal using Metalworking Tools

Two basic operations — folding and bending — transform flat sheet-metal into a shaped object. With sheet metal of 24-gauge or lighter, you can form the curves of metal cylinders and the sharply-folded corners of boxes by hand.

Before you can form final shapes, you must fold the hems and seams indicated by the pattern to reinforce and bind the cut edges of the flat metal sheet and to make them less hazardous. You can form these folds with a hand seamer while the sheet is still flat. Finish wired edges for the rims of cylindrical objects before shaping the sheet metal. On more complex sheet-metal shapes, such as boxes, cones, and tapers, add the wired edge after you complete the shaping and seaming operations. However, when forming a box, make sure to form on the flat sheet the open folds where the wire will be fitted.

For folded and grooved seams, use a hand seamer to make open-edged folds, called seam locks, before you shape the flat sheet. Leave clearance under the folds so that the layers of metal slip together easily on the finished object. Form the folds on opposite sides of the flat sheet so that they interlock.

After forming the seam locks, your net step is to make the sharp bends that define the corners of boxes and rectangular forms, and make the curved bends that shape cylinders and tapered shapes. For each kind of bend, use the appropriate stake, or you can improvise with pipes, blocks, and angle irons. To make an angular bend, for instance, secure the metal with an angle iron and clamps and crease it over the edge of the workbench. Form the sides of a box with the help of a wooden block that is cut to size and clamped to the bottom of the box. Bend up the sides against the wood.

A length of pipe clamped firmly in a vise is an adequate substitute for stakes in shaping curves, cones, and tapers. For unusual or complex curves, cut wooden formers — interlocking blocks of hardwood — in the shape you need. Clamp the two pieces of wood with the metal between them and use the vise to squeeze the sheet metal into the shape.

After you've bent and folded the metal into its final form, secure the seams by hooking the seam locks and then hammering them flat to form folded seams. To seam projects with curved sides, clamp a piece of pipe in a vise to support the operation. For boxes or open-ended rectangles, support the workpiece by attaching a length of flat bar stock or railroad rail to the edge of the bench.

For a very secure seam, finish the joint with a hand groover. Select a grooving tool with a slot about 1/16-inch wider than the seam itself. If you are forming a number of objects with grooved seams, settle on a common seam size. For example, if you plan for ¼-inch seams throughout the project, you can then finish every seam with a standard 5/16-inch (No. 2) hand groover.

Some metal-shaping operations present special problems. Attaching the base of a container to a cylindrical or tapered wall with a double seam, or wiring the rim of a tapered object, requires that you make sharp folds along curved rims and edges. You can use a pair of flat-nosed pliers provided that you wrap the jaws in masking tape to avoid marring the metal. Use a mallet and a setting hammer to crimp the folded metal around a wire to form a wired edge, or for locking the flanges together in a double seam. In turning a flange with pliers, as in shaping sheet metal with any hand tool, wear gloves and work slowly and patiently to avoid stretching or kinking the metal.

Sheers, Punches and Other Metalworking Hand Tools Used to Cut Sheet Metal

These hand-held snips, shears, and punches are used for cutting sheet metal to any shape or size. There are three standard types of aviation snips:

  • Aviation snips with a serrated blade that are curved and beveled to cut a straight line
  • Aviation snips with a right-hand curve
  • Aviation snips with a left-hand curve

Widely available brands of aviation snips have color-coded grips for quick identification in the workshop. The shape of the metalworking tool blades helps the metal to curve away from the tool as its cut, which allows the cut to progress more easily.

Hawk-billed snips have long handles and slender blades, making them especially useful for cutting curves in tight spots.

The ripping shear is handy for short, hard-to-reach inside cuts.

Punches, when tapped repeatedly with a ball-peen hammer, make holes of various sizes:

  • The solid punch pushes small circular sections out of a metal sheet
  • The hollow punch works like a cookie cutter to remove circular sections

A hand-held power shear makes quick work of big jobs. Its reciprocating blade shears easily along both straight and curved guidelines.

Cutting a Large Hole with Punch and Snips

You can cut a large hole in sheet metal with a pair of snips, but to begin the cut you'll need to punch a starting hole inside the larger hole.

Beginning the Cut with a Punch

Set the approximate center of the projected hole over the end-grain portion of a hardwood block or over a soft lead block. Set the head of a hollow punch within the scribed guideline and over the block, press down firmly and, with the flat poll of a ball-peen hammer, strike a solid blow on the end of the punch. Try to punch entirely through the metal with no more than two blows. Repeated light taps will result in a jagged edge.

Cutting with Hawk-Billed Snips

Working from above or below the metal surface, whichever is more comfortable, use hawk-billed snips to cut in an arc-shaped path from the edge of the punched hole to within¼ inch of the scribed guideline, using the technique described for aviation snips. Continue cutting just inside the guideline, periodically bending the waste metal away from your hand. When you have completed this first cut, discard the waste and then go back and cut directly along the guideline to trim the hole to finished size. Clean up any rough edges with a fine round file.

How to Make a Preliminary Fold in Sheet Metal

Using a hand seamer or sheet metal seamer, grasp the middle of the edge of sheet metal you are going to bend, positioning the jaws of the seamer so that they close at the fold line previously scribed on the metal. Tighten the adjusting screws until they butt against the metal edge. Use the edge of the lower jaw as a fulcrum by pressing down firmly against the work surface while you lift the handles of the seamer to start the bend. On a long edge, it is best to work from the middle of the piece to either side, grasping and bending the metal edge every 3 to 4 inches along the fold line. To avoid kinking the metal, bend each section only slightly, and then move on to the next section of metal, bringing it even with the previous section. Continue folding bit by bit until you have worked the edge to an angle halfway between vertical and completely closed. The edge is now ready for wiring, or for further creasing to form a folded hem or a seam lock.

Measuring Correctly for Seams in Sheet Metal

In sheet metal work, the extra material needed for each seam depends on the size of the seam, the number of folds it involves, and the thickness of the metal. For a 1-inch standing seam, typical on a large duct, you need â…ž inch extra metal for the edge with the single fold, and 1â…ž inches extra for the edge with the double fold, plus a bit extra for the thickness of the metal.

When you are planning for folded or grooved seams, both of which are typically ¼ inch wide, allow for ¼-inch folds on each edge, plus a small additional amount to accommodate the thickness of the folds. When you're using a folded seam or a grooved seam to join the lengthwise edges of a duct or a pipe, be sure that you enlarge the pattern by the width of the seam — in this case ¼ inch — to allow for the reduction in circumference caused by the seam. A standard ¼-inch double seam requires a ¼-inch allowance along the wall of the container where you will join the wall to the base. You need ½ inch of extra metal to accommodate the two folds along the edge of the base, along with small additional allowances for the thickness of the folds.

How to Make Sheet Metal Seams Flush on One Side Using a Hand Groover Tool

Grooving an Outside Seam

After you join the metal seams, support the piece of metal over a stake, pipe, or rail. Fit a hand groover tool of the proper size over one end of the metal joint and hammer it sharply to start the groove; repeat at the other end. Tip the hand groover back down the seam line and hammer it along the entire length. The three layers of metal in the joint will form a ridge down the outside of the metal object. The inner surface will stay flush and smooth.

Grooving an Inside Seam

Clamp a rail with a groove of the proper size to the edge of the work bench, rounded face up for cylindrical objects, flat face up for rectangular metal ducts and metal boxes. Position the locked seam over the groove and use a mallet to drive each end of the seam into the groove. Then use a mallet along the entire length of the metal joint from end to end to form a ridge of folded metal on the inside of the metal piece and a smooth, flush seam on the outside.


How to Make Hems and Seam Locks with Folds in Sheet Metal

Sheet metal projects can be joined together with interlocking seams made from simple bends and folds along the mating edges. Most hems and seams are made in stages, starting with the preliminary sheet metal fold.

Interlocking Folded Seams in Sheet Metal

Join the edges of a formed object by hooking the seam locks together. Then support the object on a length of pipe, a piece of rail, or either end of a mandrel stake. Use a rounded surface for a cylindrical form or a flat surface for rectangles and boxes. Turn the object until the seam is directly over the support, and then tap along its length with a mallet. Use even pressure when you flatten the seam to avoid distorting the metal.

Closing a Seam with a Seamer

If you are making a seam lock to join with another in a folded or grooved seam, slip two thicknesses of scrap metal or a thin scrap of wood under the middle of the preliminary fold. Fit the jaws of the seamer over the creased edge and the scrap, and squeeze firmly. Work along the full length of the fold, moving the scrap as you go. Then remove the scrap, and check to make certain that enough clearance remains for the fold to mate with another seam lock.

For a simple folded hem, as on the top edge of a box, leave out the scrap and close the fold completely (inset). For a double hem, fold a single-fold hem a second time, turning the edge with the seamer and crimping it closed.

Double-Seaming around a Container Base

To install a tight base in a sheet-metal container, use the technique of double-seaming.

Turning the Flange

Fit a cylindrical or tapered container wall over a section of pipe or a mandrel stake. Steady your work with one hand and use flat-nosed pliers to grasp the edge marked for folding, bending it up in small sections. Work slowly and do not bend any section sharply without evening off the rest of the edge.

As the turned-up portion approaches a right angle, remove the container wall from the support. Up-end it on the work surface and strike along the flange with a mallet to square off the bend and form a right angle.

Edging the Base

Form a matching right-angled flange around the container base by bending up the circular edge, marked off with a divider. Begin by using flat-nosed pliers to crease the edge in small sections around the base. Then position the base against the end of a piece of pipe or a mandrel stake, aligning it so that the folded edge hooks just over the horizontal surface of the pipe or stake. Use a mallet to hammer the edge down onto the curved surface, rotating the base slowly until you finish the flange at a right angle to the base.

Closing the Seam

With the base flat on a work surface, fit the wall of the container down inside the turned-up flange of the base. Then use the tapered peen of a setting hammer to bend down the edge of the base onto the flange at the bottom of the container wall (inset). Hold the hammer at a sharp angle so you don't dent or scratch the workpiece with the hammer head.

Locking the Base in Place

Support the container on a pipe or a mandrel stake. Use a mallet to turn up the joined edges of the base and walls so that they lie flat against the container sides (inset), rotating the container as you work around the entire seam.

A Wired Edge for Smooth Reinforcement on Sheet Metal

You can add rigidity to a sheet-metal box or bucket by folding the top rim around a thick wire. This detail gives a professional finish to shop-made sheet-metal projects.

Bending the Wire to Fit the Rim

Measure and cut a length of wire equal to twice the combined length and width of the box, plus twice the diameter of the wire. Clamp the wire in a vise with about 1-½ inches extending from one side. Hammer that short section to a right-angled bend, then unclamp the wire and pass through the vise an additional length equal to one side of the box. Reclamp for a second right-angled bend. Unclamp the wire, and repeat the process twice more. On the fourth side, don't butt the wire ends together right at the corner, but rather, about 1-½ inches away from the corner bend. This will strengthen the corner seams of the box and give the appearance of continuous wiring all around the rim.

Fixing the Wire to the Rim

Slip the formed wire into the folds that you have left partially open around the top of the box. Fit the box over an improvised support or the flat end of a mandrel stake. Use pliers with taped jaws to press the wire snugly into the fold at one end of a side. Tap with a mallet to bend the creased edge over the wire. Work along the side in small sections, moving the pliers as you go so that you are always holding the wire close to the sheet metal being flattened. Continue all the way around the rim, rotating the box on the support as you work.

Setting the Edge

Upend the box on the work surface and crimp the edge farther around the wire by tapping along it with the square face of a setting hammer. To complete the tucking, reverse the hammer and drive the metal edge behind the wire with the hammer's tapered peen.

How to Make Holes and Countersinks for Screw Heads in Metal

To widen the top of a hole to accommodate a tapered screw head, fit a cone-shaped countersinking bit into the chuck of a drill press or a hand drill. Drill at the slowest possible speed, and apply cutting fluid liberally. As you drill, check the circumference of the hole by setting an upside-down screw head over the hole. The two should match perfectly, so that the screw will be flush with the surface of the metal when it is in place (inset).

To inset bolt heads, make a cylindrical, or counter bored, hole with a counter bore bit 1/16 inch larger than the bolt head. Make the hole deep enough that the top of the bolt sits flush with the metal surface when it is in place.

How to Form Sheet Metal into Angles and Curves

Making a Right-Angled Bend in Sheet Metal

Align the fold line on the metal with the edge of the workbench. Lay an angle iron across the sheet, flush with the fold line and the workbench edge, and clamp it in place with two C clamps. Force the flap of metal down by hand, and then square off the bend at a crisp right angle by tapping along the length of the crease with a mallet.

To use a special hatchet stake (inset) in forming an angled bend, position the fold line directly over the stake and press down on both sides. When the fold reaches the desired angle, keep the bend fitted tightly over the sharp edge of the stake; pound with a mallet along the crease, to make the bend sharper.

How to Form Sheet Metal into Angles and Curves

Making a Right-Angled Bend in Sheet Metal

Align the fold line on the metal with the edge of the workbench. Lay an angle iron across the sheet, flush with the fold line and the workbench edge, and clamp it in place with two C clamps. Force the flap of metal down by hand, and then square off the bend at a crisp right angle by tapping along the length of the crease with a mallet.

To use a special hatchet stake (inset) in forming an angled bend, position the fold line directly over the stake and press down on both sides. When the fold reaches the desired angle, keep the bend fitted tightly over the sharp edge of the stake; pound with a mallet along the crease, to make the bend sharper.

Bending the Sides of a Metal Box

Cut a block of wood to the exact width and length of the bottom of the metal box you have planned. Center it on the cut-out sheet metal, aligning the block's edges with the fold lines. Clamp the assembly to the workbench, positioning one fold line directly over and flush with the bench edge. Bend up the side by hand, and tap along the crease with a mallet to make a sharp bend. To bend up the remaining sides, unclamp each one, turn it, then reposition the assembly and reclamp the block so that the next unbent side projects over the workbench edge.

Shaping Sheet Metal into Curves and Cylinders

Using a vise, secure a length of pipe with a radius at least 25 percent smaller than that of the metal curve or cylinder you plan, or use a conductor stake of the proper size (inset). Support the flat sheet with one edge extending just past the top of the curve, and bend down the sheet in small sections by hand or with a mallet. Move the sheet gradually across the pipe or stake. If you form the curve with bends that are separated too widely, the curve will be uneven.

Forming a Cone from Sheet Metal

Starting at one end of the metal cutout, bend the metal down over a piece of pipe clamped in a vise, either by hand or with a mallet. Slowly work the narrow end of the sheet metal cutout across the pipe, bending it sharply where you form the small opening of the cone. Move the wider end of the metal piece more quickly and bend it less sharply so that the cone tapers properly.

To shape a metal cone on a blow horn stake (inset), form the narrow end of the cone over the point of the horn, the wider end over the broad part of the stake, bending the metal gradually.

How to Fill a Sheet Metal Dent That Cannot Be Banged Out Using a Mallet

When working on a metal repair or metal fabrication project, dents in metal are often in need of correcting. Banging dents out of metal is the easiest way to fix dented metal, but sometimes metal cannot be smoothed out by banging with a mallet. It must be filled. Follow these steps to fill dents in sheet metal that cannot be malleted.

Drill Anchor Holes in the Sheet Metal

If you cannot reach the back of a dent with a hammer or a stake because the object has a double layer of metal, sand the dent and a 1-inch area around it, exposing the bare metal. Drill â…›-inch holes ½-inch apart in the dent. Be careful that you do not drill through the inside layer of metal. These holes will help anchor the filling compound.

Apply the Metal Filler for Metal Repair

Use a putty knife or other applicator to fill the dent in the metal with an epoxy mixture or dent-filling compound. Press the filler material into the drilled holes so that some of it spreads onto the inaccessible side of the metal. Build the filler slightly higher than the surface of the surrounding metal, and overlap the edges of the dented area. Allow the epoxy to cure completely. File and sand the filled metal surface to the correct level and finish of the original metal surface. Clean and paint the filler, feathering the paint into the surface of the metal object.