How to Use an Undercut Saw to Cut Door Casing


Are you a flooring contractor, a power tool enthusiast? And would like to learn how to use an undercut saw for cutting door casings? Then this article is definitely for you.

In this article, you’ll be guided step by step on how to safely and skillfully use an undercut saw.

What is an undercut saw?

An undercut or door jamb saw is a special-purpose tool designed for undercutting door casings to install tile, hardwood, or laminate floorings. Therefore, giving it a neat and seamless appearance.

This is a “must-have” tool for every flooring contractor.

An undercut saw is a combination of a circular saw and an angle grinder used for buffing out materials. It’s shaped like an angle grinder with a handle guard that steadies it on the surface for easy cutting.

Although it has a large ripping teeth blade that rotates at a high speed different from an angle grinder but similar to a circular saw. The blade is mounted on an abhor perpendicular to the body of the tool.

This provides a stable surface for non-skid sliding action and a stable surface for cutting.

Uses of an Undercut Saw

An undercut saw is used in woodworking and construction, and just like most power tools, it is versatile. It also can be used for general cuttings.

However, it is specifically designed to undercut door casings, mouldings, base, masonry, and tile to install flooring materials. This makes flooring installation faster and efficient. Since you don’t have to cut or trim flooring materials to fit around the door casing.

Cutting or trimming by hand would not only be stressful and time-consuming but would mostly not give a good result.

If you want a good result undercut the door casing and push in the flooring material to install. Leave a little gap to create an illusion of the flooring material sitting directly under the door casing.

You’re probably thinking “Why can’t I use regular or reciprocating saws?”

Well, most door casings are designed in such a way that makes it hard for regular saws to get through. And reciprocating saws can’t give a fine cut like an undercut saw would.

This is why you need an undercut saw. It was specifically designed for this purpose, and no other tool does it better.

How to Use an Undercut Saw to Cut Door Casings

Undercutting door casings is quite simple and anyone can do it with the right tool (undercut saw) and some basic knowledge.

When using an undercut saw to cut a door casing, you aim to get a perfect undercut to slide in your flooring piece. This is why it is important to consider some factors before buying or renting an undercut saw for the project:

Decide whether you want a Powered or manual undercut saw: There are two types of undercut saw. The electric undercut saw and the hand undercut saw. The electrical undercut saw is faster, less stressful, and efficient, but costly than a hand saw. If you don’t mind the price, the electric model is the best option. It is what professionals use.

Adjustable cutting depth and height: Ensure the saw has an adjustable cutting depth and height which works perfectly. This will enable you to control the blade better.

Check blade strength and quality: The saw would come with a blade, so check if the saw blade is suitable for your project. It should be made from steel with sharp teeth to cut efficiently. Also, ensure that the blade is easily replaceable. This is for when the blade gets blunt.

The longevity: When you buy a power tool such as this, your expectation is for it to last for years, so aside from the blade. Check to ensure other parts of the undercut saw like the handle guard, and the tool’s body is made with durable materials. Finally, check if it has a storage case or a manufacturer warranty. To return if the tool gets damaged within a short period of the purchase date.

Weigh the price of the model: Check to see if the chosen model is worth the price. You don’t want to buy an undercut saw that ends up not meeting the claimed quality.

You can buy an undercut saw from any hardware store or e-commerce site like Amazon. If you’re on a budget or it is just a one-time project, you may rent the electric undercut saw or opt for a hand saw.

Here is a simple step by step process of using an electric undercut saw:

Step 1: Mark the door casing before cutting

Take a sample piece of your flooring material to mark the door casing. Adjust the saw blade to align with the upper portion of the flooring material you want to install. Also, use a piece of the underlayment under the flooring piece and place cardboard if it is a tile to prevent it from cracking. This will save time if correctly done.

Step 2: Adjust the saw blade to meet the marked area

Position the saw flat on the flooring piece to meet the door casing. Make sure this is correctly done to fit the appropriate height before cutting. You don’t want to finish cutting and realize that you have an undercut too high or too low.

Step 3: Set nails deeper than your cut

Before cutting into the door casing ensure the nails in your cut line are deeper than your cut to prevent damaging the saw blade.  Do this by pushing down the nail with a hammer and a nail set. This way you have no chance of ruining your saw blade or the whole cutting.

 Step 4: Set the saw

Ensure all adjustments like depth cut, blade mount is locked down before starting the saw.

Step 5: Begin undercutting the door casing

Plug in the saw and allow the speed to regulate before cutting. Make sure your flooring piece is leveled because when you turn on the saw. It might want to wiggle a bit, so stabilize the piece with your fingers. Then position it against the marked area steading your hand. Don’t force or use your hand to guide back.  Use the wall to plunge slowly cutting in a clockwise motion until the desired depth is achieved to easily slide in the flooring material.

Step 6: Check if the flooring material fits

After undercutting the door casing. Remove the undercut wood from underneath the casing. You will have a nice flat area all the way around. Then slide in your flooring material to check if it fits seamlessly and nothing can get underneath. But if it doesn’t it is recommended to raise the saw to about 1/32 inches higher than previously done. Then recheck by pushing in your floor piece.

Step 7:  Install the flooring material

Once, your flooring material fits properly. Use a trim paint to touch up the edges of the door casing before installing the flooring material and use sandpaper or your fingernail to get out some of the rough edges from the cut. Clear out the debris with the vacuum. Then slide in your flooring to install. 

On the other hand, the same process is being followed using a hand saw, excluding the electrical aspect of it. 

Now you can see that using the undercut saw is not just efficient but fast and simple to use. Anyone can use it.

Nevertheless, whenever you use a blade tool as the undercut saw there are certain safety precautions you must take to avoid accidents. 

Below are some safety tips to observe:

  • You must ensure there’s nothing around that can jam into the saw blade. This is to prevent any fatal tool failure.
  • Always wear protective gear such as a nose mask and protective goggles to protect you from flying debris and dust. Also, use earplugs to protect your ears from the saw’s noise.
  • Use the guard handle to hold the saw. Don’t put your hand close to the blade.
  • Don’t attempt to remove debris while cutting.
  • Ensure the saw is positioned before plugging in.
  • Don’t keep the saw close to your side while it is running.
  • Don’t keep the cut-out wood between your legs or hand while sawing. Position the saw properly.
  • Be careful while changing the blade because the blade will be hot after use.
  • Always unplug the saw before changing the blade.
  • Don’t carry or unplug the saw from the cord.
  • Keep away from children, so they don’t injure themselves with the blade.
  • Don’t use it on a wet surface. It can cause electrocution.
  • Ensure there are no inflammable materials in the area because the saw might throw sparks.
  • Don’t use it to cut steel. Sparks created can cause a fire in the wall.
  • Read the operator’s manual.

Final Words

The undercut saw is a “must-have” tool to get a perfect and precise cut for installing flooring material. It’s efficient, easy to use, and gets the job done on time.

And with the above steps and safety tips, you should be able to operate an undercut saw skillfully and safely to get an overall good result.


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Jason D. Turner

Hi there! My name is Jason, a keen enthusiast in power tools and their mechanisms and the sole mastermind behind the Noisy Tools. Working in a multi-national construction firm in Brooklyn for over a decade, I have developed a fair flair for different construction devices, gadgets, and their diverse operational aspects. By the dint of this platform, I have researched and reviewed various tools with utmost details of even the most trivial matters that will provide valuable insights for any prospective user.

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