Curtain Grommets for Drapery Workrooms: Choosing 18mm, 30mm, or 40mm

Curtain grommets are two-piece metal sets, a grommet and a matching washer, that finish the holes in a drapery header. Select the size primarily by curtain rod diameter, choose brass or 304 stainless steel based on exposure and the desired finish, then set samples in your actual header to confirm the grommet closes correctly.

Stimpson carries curtain grommets in three metric sizes and two base metals. Keith Gentilin, our Vice President of Sales & Marketing, recommends: “The grommet should be slightly larger than the diameter of the curtain rod, and the material should be suitable for your environment. Stainless steel is more popular outdoors, particularly in marine environments, while brass and nickel-plated brass are popular choices indoors. Then test the fit in your material. We can help with complimentary sample settings.”

Whether the grommet sets properly is a different question. Fabric thickness, layer count, interfacing or header reinforcement, such as buckram, and overall header construction determine whether the set can close through the header. Length under the flange increases with size, from .331″ on the 18mm to .433″ on the 40mm, but the size chart cannot tell you how a set will close in your header. Testing does.

Which Curtain Grommet Do You Need?

Dimensions are as listed on each product page. All four come in boxes of 100, 500, or 1,000 sets.

Typical Uses for the 18mm Set

The 18mm listing names shower curtains, outdoor and marine drapery, and décor, with slim rods, cables, and wires. Use it for diameters up to 5/8″ (16mm), and confirm clearance against the .701″ hole before ordering. It comes in 304 stainless only.

Typical Uses for the 30mm Set

The 30mm listing covers diameters up to roughly 3/4″ and names medium-weight residential and hospitality drapes as the typical application, along with commercial design and trade show and display panels.

Typical Uses for the 40mm Set

The 40mm brass set is listed for diameters up to approximately 1-1/8″. Its listing names heavy drapes, theater curtains, and oversized decorative panels. The 40mm stainless set takes the same range, and its listing includes pool-area and outdoor drapery. The 2.441″ flange also puts a larger ring on the face of a wide panel. Even on a heavy panel, curtain rod diameter sets the grommet size, not panel weight.

Brass or 304 Stainless: Match the Metal to the Setting

Polished brass curtain grommet and washer.

Brass for interior work. Polished brass pairs with wood poles and classic hardware. The polished nickel finish coordinates with chrome and brushed-metal hardware. Both are finishes on the 30mm and 40mm brass sets. For more on how finishes compare, see metal grommet finish options.

Polished silver-finish curtain grommet and washer.

304 stainless for moisture exposure. 304 stainless steel is the corrosion-resistant option in this line, available in 18mm and 40mm. Stimpson’s article on 304 stainless steel for marine applications covers the metal in more detail.

As a starting point, if the drape will be exposed to water, humidity, or outdoor conditions, evaluate 304 stainless first. Exposure conditions vary by site, so confirm suitability for your specific environment with your local Stimpson Sales Rep before you specify it. If the drape hangs in a dry interior, choose the brass finish that matches the hardware.

Setting Curtain Grommets: One Tool per Size

Each size sets with its own curtain set hand drive tool, driven with a brass mallet that is sold separately:

• 18CGWTS: Sets the 18mm stainless steel set (18CGWSS).
• 30CGWTS: Sets the 30mm brass set in both the polished brass and nickel finishes.
• 40CGWTS: Sets the 40mm brass and 40mm stainless steel sets.

Each tool is listed only for its own size, so plan one tool per size you run.

For higher volumes, ask your local Stimpson Sales Rep about machine options. The Jopevi J-25 pneumatic grommet machine can set all three curtain grommet sizes in prepunched material, with separate tooling for each size. Confirm cut-and-set compatibility before planning around it.

Test in Your Fabric Before the Production Run

No curtain grommet fits every fabric. Header construction, fabric weight, layer count, and the hole you cut all change how the set closes. A set that closes cleanly in a lightweight sheer can behave differently in a lined blackout panel. Use a 3/4″ hole punch for the 18mm set. Ask your local Stimpson Sales Rep to confirm the cut size for the 30mm and 40mm sets.

Ask your local Stimpson Sales Rep about complimentary samples, including installation into your materials. Setting samples in your actual header confirms the set closes correctly before you order production quantities.

Curtain Grommet FAQ

What size curtain rod fits a 30mm grommet?

The 30mm listing gives a maximum of roughly 3/4″ in diameter. Test the fit on your actual hardware before ordering.

Is a 40mm curtain grommet the same as a #12?

Its 1-9/16″ (1.547″) hole is comparable to a standard #12 curtain grommet. Numbered sizes are not used consistently across suppliers, so compare hole diameters rather than size numbers.

Do I need a special tool to set curtain grommets?

Yes. Each size has its own hand drive tool, used with a brass mallet that is sold separately: 18CGWTS, 30CGWTS, or 40CGWTS.

Get the Right Curtain Grommet for Your Next Order

Contact your local Stimpson Sales Rep to discuss your application, or call (877) 765-0748. Ready to order? Visit the official Stimpson webstore. Order Monday through Friday and enjoy same-day shipping on all orders placed by 3:00 PM E.T.