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How To Cut A Straight Line With A Utility Knife (7 Tips!)

straight line with utility knife

Learning how to cut a straight line with a utility knife is bound to pay dividends at the end of many of your home renovation and DIY projects. Whether you are working on an intricate design, replacing drywall, or installing vinyl plank floors. 

Just imagine how bad a new floor would look if the installer didn’t take the extra time and care to get the cleanest, straightest cut with his utility knife. 

7 Tips On How To Cut A Straight Line With A Utility Knife

No one wants a floor with jagged edges and cuts of material that just don’t fit the space. Taking the time to cut a straight line at the start prevents a mess at the finish.

A good quality utility knife is among the top tools every DIY or home maintenance expert needs in the garage. As with any tool, a utility knife should be used safely, and with skill and precision. 

There are basic tools and tips to accompany your utility knife that will give you a straight, more appealing cut.

We’re going to share 7 simple tips to help you learn how to cut a straight line with a utility knife.

1.  Use a Metal Straight Edge, not Wood or Plastic

The average plastic or wooden ruler or yardstick will cause you headaches when trying to achieve the perfect cut with your utility knife. Utility knives are extremely sharp.  

The knife will inevitably poke, jab, and dig into softer material like plastic and wood. When the edge you’re using has imperfections, those imperfections may translate to the material you’re cutting. A sturdy, metal ruler is a much better option, as your knife is unlikely to penetrate the edges.

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The potentially jagged edges of a wooden or plastic ruler are also a safety concern. You don’t want your knife to hit a nick in the ruler while you’re cutting, and suddenly steer your knife off its path. That could lead to a painful cut!

You are much more likely to achieve a clean, straight, safe cut with an impenetrable straight edge made of steel or some other tough metal.

2.  Use an Appropriately Sized Straight Edge 

If you’re cutting a floor plank crosswise, you don’t need a 24-inch metal ruler for a material less than six inches wide. Something smaller, like a speed square, will give you better grip while you cut. 

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However, if you’re cutting the same floor plank length wise, a longer straight edge will be more helpful. If possible, you want your straight edge to be long enough to extend the entire cut, so that you do not have to move your straight edge in the middle of a cut. 

Moving your straight edge mid-cut could cause your line to become crooked, if not done very carefully. It’s a good idea to have two or three straight edge rulers and tools that vary in length, so you are prepared for any cut.

3. Use a Cutting Mat with a Grid

There are a number of reasons to have a cutting mat within reach while you are using your utility knife. 

First and foremost, you do not want to damage the surface beneath the material you are cutting.  Utility knives are sharp, and they could cut into or damage a table, workbench, or other surfaces that weren’t necessarily designed for cutting with utility knives.

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Second, a cutting mat is practically impenetrable. It won’t get the same nicks and abrasions that a work bench or table might suffer.  

Cutting on a surface that has been damaged by a utility knife can actually cause your cut to be less straight. The smooth surface of a cutting mat will help ensure a smooth, straight line on the material you’re cutting. 

As with using a damaged straight edge, cutting on a bumpy or damaged surface could cause injuries. It’s important to do everything you can to ensure a smooth cut.

Finally, many cutting mats have a grid display on them. You can use the grid as a guide to avoid a diagonal cut. 

4.  Use Adhesive to Keep Your Straight Edge in Place 

Placing tape on the bottom of your ruler, speed square or straight edge can help keep the guide in place while you cut. 

Depending on the material you are cutting, it may be challenging to keep your straight edge in place while you cut your project carefully along the ruler’s edge. 

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It’s important to apply pressure, so that your straight edge does not move while you are cutting; but, sometimes that very pressure can cause your ruler to shift slightly. 

A slip like this is both a safety concern, as your hand might slip into the path of the blade, and it could compromise your cut.  

Make sure to use a tape that is easy to remove, like painter’s tape, to avoid damaging the material you are cutting. A tape like painter’s tape will pull off the surface of your project without leaving residue or causing damage.

5.  Don’t Cut All the Way Through your Material at Once 

This rule is particularly true if you’re working with a thicker material like carpet, flooring, or even cardboard. 

To achieve a smooth, straight cut when using a utility knife, you want your strokes to be lighter, and you want to avoid applying excessive pressure.

Best practice with your utility knife is to lightly drag the knife across the surface of your material first, creating an initial track for your knife to follow. 

Then slowly break the surface and cut deeper over several slices in the same location. Applying the amount of pressure it takes to cut all the way through thick material in one try can lead to rigid edges. 

6.  The Quality of Your Knife Matters 

What should you look for when buying a quality utility knife for your home? The best utility knives are expertly designed to help you make the straightest, cleanest cuts possible. 

There are four considerations when finding the perfect utility knife for your toolbox:  price, retractable vs. folding, ease of blade swap, and functionality. 

If you are not sure where to start considering your options, The Clever Homeowner has you covered with our Five Best Utility Knives for Homeowners and General Home Use. We listed the pros and cons of each knife that made our list, from safety considerations to the price tag.

7.  Have Extra Blades on Hand 

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It is simply impossible to achieve a straight cut if your utility knife has a dull blade, and these blades were not designed to last forever. They must be replaced when they become dull after several uses. 

When buying a utility knife, it is good practice to purchase extra blades, if your knife doesn’t come with a set of spares. 

Changing your blade can vary depending on the tool you buy, so make sure to read the instructions or ask the retailer about best practices with your knife.

Finally, make sure you dispose of used blades safely. If you’ve been to a construction sight, you have likely seen the plastic bottles with utility knife blades thrown into the bottom. 

This helps ensure they won’t break through a garbage bag, on the way to the dump,  or be left to injure an unknowing person walking in the project site.

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