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How To Match Screws To Anchors

Buying suitable screws and anchors to hold the weight of your object can be tricky. They'll fall in if it's too big, and they'll slip out if it's too small. Using the wrong screw is one thing, but what if a project fails? We have done some research for you to ensure you pick the right screw that matches the anchor.

Disclosure: We may get commissions for purchases made through links in this post.

Here's what you should do to figure out which screws will work with the anchor you're going to buy:

  • Understand screw sizes
  • Know the size of screw to use for your project
  • Choose the suitable anchor

Not sure what screw size to get? Or what type of anchor to use? Keep reading to learn about the suitable screw and anchor for your project.

A screwdriver and dowel in a concrete wall, How To Match Screws To Anchors

Understanding Screw Sizes

Most packaging for screws sold in the United States has measurements written in imperial units. It's hard to find a company that advertises the number of threads per inch in their products. Instead, they list them by their gauge and length.

Screw organizer

An item marked 10 x 2 inches in the packaging tells it's a #10 gauge, 2-inch screw. Now let's say it has a thread count. For instance, 10-35x2 inches screw, you'll see a number in the middle.

Unless you are familiar with the various screw sizes listed on the packaging, sizing the correct screw in both metric and imperial measurements may be difficult.

For instance, when you need a screw, you often can't find one quickly. And when you do, it doesn't match the anchor size or hole diameter.

So how are screws measured? Keep reading.

Screw Diameter or Gauge

When determining screw diameter, measure the thread diameter rather than the head diameter. An inch measurement is a whole number and a #.

Keep in mind that these numbers are directly proportional to the diameter, so the larger the number, the larger the diameter of the screw.

Screw Length

Measuring a screw's length starts where its head settles on the material after you drill it.

Screws must be long enough to pass through holes in the material you'll use for your project. Follow the steps below to find out the length of different screws:

  • For countersinking screw- Beginning at the top of the screw head, measure the screw length to the bottom. Any screw with a drive that can penetrate a surface, such as trim-head screws, qualifies for this.
  • For partial countersinking screw- Measure its length from the widest point of the head or where the screw head meets the surface of the workpiece to the screw tip. It is how you measure an oval-head screw.
  • For non-countersunk screws- Measure the screw length from the bottom of the head to the tip. It applies to hex, button, pan, truss-head, and round screws.

The screw length should be half the thickness of the bottom material, for example, a 3/4-inch screw in a ½-inch thick material.

Screw Thread Count/Pitch

You can calculate Threads Per Inch (TPI) by counting the threads on a screw and dividing them by the length.

Also known as thread count, 20 represents 20 threads per inch in US screw sizes. Metric fasteners specify a thread pitch, which is how far apart the threads are, so 1.5 pitch means 1.5 millimeters.

Know the Size of Screw to Use for Your Project

Screws with longer lengths typically give you more support, allowing you to load them up with more weight. Learn how to use the screw gauge if it comes with instructions.

When in doubt, use a potential too-large screw rather than a potentially too-small screw. You can also check this list of standard screw sizes for various recommended uses.

Screw Size For Lightweight Items

  • #4 screw: These small screws have a diameter of 7/64 inches and come in lengths ranging from 3/8 to 3/4 inches. You can use them for crafts and light-duty hinges.
  • #6 screw: Also known as a light-duty screw, it has a diameter of 9/64 inches and comes to lengths of 1/2 inches. It works best for picture frames, drawers, cabinets, and light-duty furniture.

Size of Screw For Medium-Weight Items

Man assembling the closet with wooden shelves wall installing a shelf

  • #8 screw: It is 5/32 inches in diameter and is an excellent all-purpose screw. The #8 is available in lengths ranging from 5/8 to 3 inches.

It is appropriate for light wood construction, such as assembling a 1-yard shelf, internal doors, and mounting a TV on stud walls.

Screw Size For Heavy-Weight Objects

  • #10 screw: It has a diameter of 3/16 inches and is available in lengths ranging from 3/4 inches to 4 inches. You can use this screw for decking, kitchen cabinets, storage sheds, and more.
  • #12 screw: It has 7/32 of an inch in diameter. You can use it for heavy-duty use. They range in length from 3/4 inches to 6 inches.

Choose the Suitable Anchor

Wall anchors or wall plugs provide support to screws. It is necessary to install the anchor before the screw to see if it fits tight inside the material. The screw goes inside the anchor once the anchor is in place.

Screw anchor set against a wooden background

Once you've decided what type of screw is suitable for the project, you need to choose the anchor.

Depending on the task, also consider the anchor's diameter and length. These will assist you with matching fittings:

  • Wall anchor diameter- It determines its mechanical strength. Hence, this should play a substantial role in your decision.
  • Wall anchor length- Take the thickness of the wall or ceiling into account when choosing an anchor. Choose the longest fixing that the diameter allows. Keep in mind that the longer the fixing, the more secure the fixing.

Anchors differ depending on the material used, and each type provides a different level of support. Below are some examples of an anchor.

Anchors for Hollow Material

Screws with dowels on a table

Plastic Anchors

An anchor like this can hold objects from 11 pounds to 175 pounds.

  • Yellow: Used for screw sizes 1 to 3. They fit into a 4 mm drill bit.
  • Red: Used for screw sizes 8 to 9. They suit into a 6 mm drill bit.
  • Green: Used for screw sizes 10 to 12. They fit into a 6.5 mm drill bit.
  • Blue: Used for screw sizes 14 to 16. They work best 8 mm drill bit.

Keep in mind that not all brands adhere to the same color standards.

Find this assorted wall anchor kit with screws on Amazon.

Butterfly Anchors

It has four 'wings' and is perfect for shallow holes. Using these wall plugs, you can hang paintings, light mirrors, and other lightweight items.

Anchors for Solid Materials

Steel Bolt Anchor

Steel bolt anchors function similarly to expansion plugs. Bolts and nuts make these anchors strong enough for heavy loads.

Hammer-in Anchor

There's a special screw that goes in these wall plugs. It's perfect for installing wooden pilings, ceiling panels, and more.

Should Screws be Longer Than Wall Anchors?

Ensure the screw doesn't go longer than the anchor. A screw not well seated in the anchor can lead to a loose fix. An anchor will hold better if it is flush with the surface.

Should Drill Bit be the Same Size as Wall Anchor?

Drilled set for a drill

The drill bit size for the anchor is determined not only by its size but also by its type. Anchors are for lightweight applications and typically require a 1/4- to 3/8-inch drill bit. A toggle anchor is for heavy-duty use and needs a 1/2-inch drill bit or bigger.

You can use a pilot hole chart to determine the best drill bit for your anchor and screws.

Can You Reinsert a Screw Into a Wall Anchor?

It depends on the type of wall anchor you use if you can reuse the combination anchor and screw. If you intend to reinsert a screw into a wall anchor, use a reusable anchor.

Click here to see this removable and reusable anchor and screw set on Amazon.

High-grade mixed plastic and metal anchors are more expensive and have reusable options. If you unscrew the screw, they retract so you can reuse them.

Is There a Way to Stop my Wall Anchor From Spinning?

If your wall anchor continues to spin, remove it and replace it in a different location. Drill, pull, or push your wall anchors.

It does not imply that you used the incorrect size anchor or that the hole is too large. You only chose inappropriate material for the anchor.

To Sum it Up

This post touches on all the basics of screw and anchor selection, with a general overview of the most commonly used options. Matching anchors and screws make a difference in how well they hold weight.

Before installing any anchor, check the packaging recommendations to know how much weight it supports and how long the screw should be. Consult a professional if unsure of the right size screw and anchor.

Learn more about screws and anchors for your upcoming projects by checking out these posts:

How Far Should A Screw Go Into A Stud?

How Much Weight Can Drywall Hold [Is It Enough For Your Home Project]?