How To Cut Hardboard

While hardboard lives up to its name, it is not difficult to cut. Even the harder, tempered variety of this compressed fiberboard can be cut with relative ease. All you need are commonly available woodwork tools and a basic understanding of the techniques involved. 

How Do You Cut Hardboard?

Cut deep grooves on both sides of the board with a utility knife, then snap the wood along the cut line. Alternatively, cut the hardboard with a hand or power saw, and if the workpiece is Masonite, make sure the saw’s teeth cut into the smooth front side of the board.

Method 1: Power Saw

You can cut through large quantities of hardboard (also called high-density fiberboard or HDFB), quickly with most kinds of power saws, including:

• Circular saws
• Table saws
• Miter saws
• Jigsaws
• Band saws

The ideal tool depends on the kind of cut you need to make. You don’t need to think about ripping or cross-cutting since HDFB is composite wood and has no grain. Factors to consider are the thickness of the board, the length of the cuts, and whether you need to make a straight or curved cut.

Circular saws and portable table saws are preferable for executing long straight cuts. These saws are also ideal for cutting thicker piece of HDFB. Miter saws are a make short, angled cuts in small sections of hardboard. Jigsaws and band saws are the tools of choice for cutting curved lines. 

Step 1: Select An Appropriate Saw Blade

Selecting an appropriate saw blade like the best jigsaw (or cutting disc) for cutting hardboard is critical to achieving a neat, accurate cut!

For cutting hardieboard siding (very similar), I personally prefer a jigsaw.

The first point is that blades made from carbide work most effectively for cutting through HDFB.

The next critical point is the size and geometry of the blade’s teeth. Fine-toothed blades are optimal for HDFB – look for the following characteristics: 

• Small teeth
• High teeth per inch (TPI) ratio
• Gentle rake angle 
• Thin 

Though HDFB is hard, it can potentially chip or splinter because it is a composite wood made from heavily compressed wood fibers. A thin, fine-toothed sharpened circular saw blade gives you the best chance to slice through hardboard without creating jagged, broken edges.

Jigsaw blade for plywood exhibit the above characteristics and are excellent for sawing through hardboard. 

Step 2: Measure And Mark The Hardboard

Take the necessary measurements with a tape measure or ruler.

Mark the intended cut line on the board with a pencil. You can also scribe (scratch) the wood with the tip of a sharp tool blade. 

At this point, some people place adhesive tape along the marked line (to lower the risk of breaking or splintering the board), but this is optional.  

Step 3: Position The Workpiece Correctly

Logically, if you are working with a table saw, a miter saw (or a mounted best circular saw or jigsaw), place the board on the tool’s table, resting snugly against the fence.

When using a hand-held circular or jig saw, lay the hardboard on a workbench or a suitably flat, stable surface. The marked line where you intend to cut must extend sufficiently far beyond the edge of the work surface!

If you are working with masonite (hardboard produced through the wet, Mason method), notice that the front side is smooth and the underside is roughly textured. 

So, to achieve the neatest results, position the masonite hardboard with the front side oriented opposite the direction of the table saw blade’s cutting motion. For example, if you use a table saw, you should position the masonite workpiece facing upward because the saw’s blade cuts downward (anti-clockwise).

If the HDFB was produced with the dry method, it is typically smooth on both sides (note that some hardboard is made using a wet-dry method). Just like how to use dry wood slices. In this case, you can orient the board with any side facing up or down (depending on which side will be visible after the project is complete).

Step 4: Stabilize The Workpiece With Clamps (Optional)

Stabilizing the piece of HDFB with your hand or foot works fine in most instances. However, if you have sufficient time, it is advantageous to secure the board with woodwork parallel clamps. Clamping the board down will provide maximum stability while allowing you to concentrate on operating the hand-held power saw.

Step 5: Set Up A Guideboard If Appropriate

If you need to make straight cuts using a hand-held jig or best circular saw, it is advantageous but not essential to use a guideboard. 

You can improvise this guiding device from a long, straight piece of off-cut wood. Set up the guideboard by clamping it to the top side of the hardboard, ensuring it is aligned with the marked line. 

Step 6: Put On Protective Gear

Power saws are potentially dangerous tools, so it is prudent to wear protective gear like goggles, a mask, and cut-proof gloves.

Step 7: Make The Cut

The next step is to execute the cut.  

Start the power saw and cut the piece of HDFB along the marked line. Use the fence or guideboard to keep the blade moving in a straight line (unless you’re cutting curves).

It is essential to cut in a slow and controlled motion, taking care to apply gentle pressure (never force the blade through the hardboard). This technique is particularly crucial at the start and end of the cut. 

Step 8: Sand The Cut Edges 

The final step is to smooth the edges of the cut with sandpaper. Using sandpaper with a fine-grit rating of P220 or P320 is generally suitable to produce a satisfactorily smooth finish on the piece of hardboard.

Method 2: Utility Knife

The most convenient way to cut HDFB is with a utility knife. You don’t use the knife to cut right through the hardboard. Instead, you use the knife to score the board deeply, then you snap the board along the scored groove.

Here are the steps to follow. 

Step 1: Measure The Board And Mark The Cut Line

Take the tape measure or ruler and take the necessary measurements to size the board.

Mark the board using a pencil (or the tip of the utility knife blade) to indicate the line you want to cut. Make sure to also mark the opposite side of the HDFB in the same place. 

Step 2: Position The Workpiece

Place the piece of hardboard on a workbench or similarly smooth, flat, and stable surface. 

When cutting masonite, orient the workpiece with the smooth, front side facing upward. If you are working with dry-made hardboard (with both sides identically smooth), place the chosen front side facing up. 

Step 3: Secure The Board If Appropriate

You may want to make the board more stable by securing it to the workbench or surface with clamps. This step is optional but worthwhile if you have the time (and access to clamps)!

Step 4: Affix The Ruler Or Guideboard (Optional)

You can opt to hold the ruler or guideboard, but clamping these cutting guides to the hardboard makes it easier to cut with accuracy and control.

Step 5: Cut A Scored Groove

Press the utility knife blade against the cutting guide (see above) at one end of the hardboard.

Make the first two or three cuts with light pressure, passing the blade in an uninterrupted, swift motion across the length of the board. Then apply more force to the blade as you execute the last two or three cuts. 

Once you have created a deep groove running along the cut line, flip the piece of HDFB over and repeat the process in the same place but on the opposite side. Now you have a scored cut line on both sides of the workpiece. 

Step 6: Snap The Board 

Complete the cut by snapping the hardboard along the scored groove. 

To perform this step, place the workpiece with the groove aligned with the straight edge of a stable, elevated work surface. The part of the board you plan to snap off should protrude over the side. 

Next, lean firmly on the board with one hand and hold the overhanging side of the board tightly with the other. Finally, use a powerful downward movement to snap off the overhanging section of the workpiece along the scored groove.

Step 7: Smooth The Cut Edges With Sandpaper

Smooth the newly-cut edges with fine-grit sandpaper to give the piece of HDFB a neatly finished look and feel.

Frequently Asked Questions

Conclusion

Hardboard is straightforward to cut with conventional woodwork tools and cutting methods. You can score HDFB with a utility knife and then snap the board or use a power saw with a fine-toothed blade to cut the material (like an ordinary piece of timber).