How to Cut a Screw Shorter: Best Tools by Screw Size

You're installing a handle or a bracket, and the screw is too long. The tip pokes out the other side. If you don't have a screw of the right length on hand, you can cut a longer one down to size.

To cut a screw shorter, pick your tool by the screw's size. For thin machine screws up to about 1/4 inch (6 mm) in diameter, a screw cutter cuts them without ruining the threads. For thicker or harder screws, thread on a nut first, then cut with a hacksaw or an angle grinder.

This guide covers how to find the right length, how to cut a screw with each tool, and how to fix the threads after cutting.

What to Decide Before You Cut a Screw Shorter

Before you cut, see whether you can avoid cutting at all. If you can't, decide on the length first.

A cut screw can't be made longer again, so settle the length before you pick up a tool.

If the Screw Is Only a Little Too Long, You May Not Need to Cut It

Start by checking how far the screw sticks out once it's installed. If it's only a few millimeters, you can match the length without cutting. There are two ways:

• Add a washer under the screw head to reduce how far it sticks out

• Buy one shorter screw

Adding a washer takes no tools, and the screw stays as it is. Cut the screw only when a washer isn't enough, or when you can't get a screw of the right length right away.

Find Where to Cut by Test-Fitting the Screw

When the screw is too long even with a washer, cut it. To find where to cut, push the screw through the parts you're fastening and follow the three steps below.

Leaving 2 threads past the nut means every thread inside the nut is engaged, so the screw holds at full strength. If you can't test-fit the screw, measure the thickness of the parts and use the formula under the diagram to get the cut length.

How to Choose a Tool to Cut a Screw

Choose a tool based on whether you'll use a nut, and on the screw's size and hardness. Here's what works best for each:

If you cut machine screws between 1/8 and 1/4 inch (about 3 to 6 mm), keep a screw cutter like the J.KOGU Machine Screw Cutter on hand. A nut threads on right after the cut, with no filing. With a hacksaw, you usually have to file the edge of the cut before a nut will go on.

The Machine Screw Cutter comes in an inch model that cuts #6-32, #8-32, #10-24 and 1/4"-20 screws. A metric model cuts M3 to M6 screws.

How to Cut a Screw Shorter with Each Tool

The way you cut a screw depends on the tool. Each section below takes you from the first cut to the finished screw, so you only need to read the one for the tool you have.

With a Screw Cutter

A screw cutter cuts a screw when you thread it into a hole in the tool and squeeze the handles. Each hole fits one screw size, so use the hole that matches your screw. Follow these steps:

1. Push the screw through the parts you're fastening, mark the cut point with a permanent marker, and remove the screw

2. Pick the hole that matches the screw size

3. Thread the screw into the hole and stop when the mark lines up with the blade (the seam between the two plates)

4. Squeeze the handles to cut

5. Unscrew the screw from the hole

The J.KOGU Machine Screw Cutter cuts as long as there's at least about 5 mm (3/16 inch) under the screw head, so it also works when you need a short screw.

The Machine Screw Cutter isn't made for bolts or hardened screws. Follow the product manual for detailed instructions.

With Diagonal Cutters

Screws up to about 1/8 inch (3 mm) thick can also be cut with diagonal cutters, as long as they can cut hard wire such as piano wire. The J.KOGU 8.5" High Leverage Diagonal Cutting Pliers are one example.

Follow these steps:

1. Push the screw through the parts you're fastening, mark the cut point with a permanent marker, and remove the screw

2. Clamp the screw in a vise or with a clamp

3. Line the cutter blades up with the mark, square to the screw

4. Squeeze the handles firmly to cut

5. Smooth the sharp cut end with a metal file

With a Hacksaw

A hacksaw works on screws of any size. Thread a nut on before you cut, and the threads get cleaned up when you take the nut off. Follow these steps:

1. Push the screw through the parts you're fastening, mark the cut point with a permanent marker, and remove the screw

2. Thread a nut onto the screw and run it past the mark toward the head. Two nuts give the vise more to grip

3. Clamp the nut in a vise

4. Saw at the mark, right next to the nut

5. Lightly file the edge of the cut with a metal file

6. Unscrew the nut. As it passes over the cut end, it pushes the damaged threads back into shape

Use a fine-tooth blade made for metal. As a rule of thumb, at least three teeth should be in contact with the material. Thinner material needs more teeth, and a fine blade has 24 to 32 teeth per inch (TPI).

Small screws are hard to hold in a vise, so you can also hold them with pliers. When you grip the threads, soft-jaw pliers like the J.KOGU 6.5" Soft Jaw Combination Pliers hold the screw without scratching it.

With an Angle Grinder

An angle grinder cuts thick or hard screws quickly. Fit it with a cut-off wheel made for metal. Follow these steps:

1. Push the screw through the parts you're fastening, mark the cut point with a permanent marker, and remove the screw

2. Fit the grinder with a metal cut-off wheel

3. Thread a nut onto the screw and run it past the mark toward the head

4. Clamp it in a vise or with a clamp

5. Put on safety glasses, gloves and earplugs

6. Cut slowly along the mark

7. File the cut end, then unscrew the nut

How to Fix a Cut Screw When the Nut Won't Thread On

If the nut won't go onto a cut screw, the threads at the cut end are crushed. You can fix them in two ways:

• Chamfer the edge of the cut with a metal file

• Recut the crushed threads with a thread file

Start by lightly filing the edge of the cut at an angle with a metal file. Just taking off the sharp edge widens the opening, so the nut starts more easily.

If the nut still won't go on, use a thread file. A thread file has teeth shaped to match the threads. Lay it across a few good threads, then move it like an ordinary file to recut the crushed ones.

Safety Tips for Cutting Screws Shorter

Keep these three things in mind when you cut a screw shorter:

• Screw cutters and diagonal cutters can't cut hardened screws

• A freshly cut screw is hot

• Wear safety glasses whenever you cut screws

Screw Cutters and Diagonal Cutters Can't Cut Hardened Screws

Screw cutters and diagonal cutters can't cut hardened screws. To cut a hardened screw, use an angle grinder.

For example, some screws of these types are hardened:

• Drywall screws

• Self-drilling screws, which drill their own hole in sheet metal

• Sheet metal screws

A Freshly Cut Screw Is Hot

A screw is hot right after you cut it. With a hacksaw or an angle grinder, friction between the blade and the screw creates heat.

Let the cut end cool for a moment before you touch it.

Wear Safety Glasses Whenever You Cut Screws

Wear safety glasses with every tool you use to cut screws. With an angle grinder, also wear gloves and earplugs.

Key Takeaways: How to Cut a Screw Shorter

When you cut a screw shorter, decide on the length first. If you're using a nut, leave 2 threads past the nut. If the screw is only a few millimeters too long, a washer may save you from cutting it.

Choose your tool based on whether you'll use a nut, and on the screw's size and hardness:

• Machine screws held with a nut (1/8 to 1/4 inch, about 3 to 6 mm): cut with a screw cutter

• Thin screws without a nut (up to 1/8 inch, about 3 mm): cut with diagonal cutters made for hard wire

• Screws thicker than 1/4 inch (about 6 mm): thread on a nut, then cut with a hacksaw or an angle grinder

• Hardened screws: cut with an angle grinder

If you often cut machine screws between 1/8 and 1/4 inch (about 3 to 6 mm), the Machine Screw Cutter gets the job done faster, because a nut threads on right after the cut.