Running Pliers vs. Grozing Pliers, understanding the differences

Running Pliers vs. Grozing Pliers: When to Use What in Stained Glass (and Why It Matters)

Let’s be honest—glass cutting can feel like defusing a bomb when you’re just starting out. You’ve made a perfect score, your hands are sweating, and now you’re staring down your tools like they’re wires labeled “DO NOT TOUCH.” But fear not! Knowing the difference between running pliers and grozing pliers—and more importantly, when to use each—will take your glass breaking from nerve-wracking to second nature.

First Up: Running Pliers – Your Go-To Glass Breaker

If stained glass tools were characters in a buddy cop movie, running pliers would be the calm, reliable veteran who always gets the job done. They’re designed for long, straight, or gently curved breaks—basically, any time your score line looks like a confident decision. These pliers apply even pressure on both sides of your score, pushing up from the bottom and down from the top to “run” the break along the line. When used properly, the glass practically breaks itself.

Here’s the trick: the curved jaws of running pliers should align with your score line, and the adjustable set screw should always face up. That screw prevents you from Hulk-smashing your glass by accident. Place the jaws on either side of the score and give the pliers a firm but gentle squeeze. Voila! The break travels neatly down the line, like a zipper opening up your masterpiece. They're perfect for breaking larger pieces after a good score—just don’t expect them to help you with tight corners or tiny notches. That’s someone else’s job.

Then There’s Grozing Pliers – The Unsung Heroes of Detail Work

Grozing pliers may look small and unassuming, but don’t be fooled—they’re the secret weapon in your stained glass toolbox. These are the pliers you reach for when you need finesse, not brute force. They’re ideal for removing narrow strips, nibbling away at curves, or snapping off little bits where your running pliers just can’t reach.

One jaw of the grozing pliers is flat (that’s the top), and the other is curved (bottom). Place the flat side against your glass, right behind the score line—not across it—and gently snap off the piece. If you’ve got a rogue corner left behind after using running pliers, grozing pliers can tidy it up with precision. They're also your best friend when cutting inside curves or tight shapes that no other tool can reach.

Pro tip: don’t treat these like tweezers—get a firm grip, but don’t crush the glass. Practice makes perfect, and yes, you will probably crunch a few pieces along the way. Welcome to the club.

And Then There’s the Skinny Guy: Narrow Grozing Pliers

Just when you thought grozing pliers couldn’t get more precise, enter the narrow-tip version—the surgical tweezers of the stained glass world. These bad boys are designed for the really tight spots, like those annoying inside curves that standard grozing pliers look at and say, “Nope.”

Narrow grozing pliers work just like their full-sized cousins, but their smaller jaws let you get in closer without accidentally chomping off something important. When you’re working on an intricate piece and the space is too tight for standard pliers, these are your glass-saving heroes. Just butt the narrow tip right up to the score line, give a gentle but firm squeeze, and pull the glass away like you’re peeling off a stubborn sticker—with precision, not rage.

A word of caution: because the tips are smaller, it’s also easier to apply too much pressure and shatter your delicate piece like a potato chip under a boot. So go easy. These pliers are more “gentle persuasion” than “brute force.”

Which Pliers Do I Use When?

Use running pliers when your score is clean, continuous, and mostly straight or just gently curved. You’re looking for one satisfying, controlled break across the glass.

Use grozing pliers for narrow cuts, inside curves, cleaning up stubborn edges, and removing small sections after the main break.

Use narrow grozing pliers for extra-tight inside curves, areas too small for standard grozing pliers, and surgical-level glass removal when precision matters.

If you’re attempting a tricky curve and reach for running pliers, you’ll probably hear that telltale crack followed by a sigh of regret. On the flip side, if you try to snap a big straight line with grozing pliers, you’ll be at it all day—and your hands won’t thank you.

Practice Makes Confident Cuts

Once you understand which tool does what, the best thing you can do is practice. Grab some scrap glass and try this drill:

Score a few straight lines and break them with your running pliers. Then, practice nibbling off tiny corners with your grozing pliers. Finally, try breaking a curved score and cleaning up the edge to fit a pattern piece.

And if you're still struggling to remember which way is “up” on your pliers—no shame in drawing little eyeballs on the flat jaws. Yes, really. It works.

Quality Tools Make All the Difference

At the end of the day, the tools you use matter. Not all pliers are created equal—cheap ones can crush, misalign, or just plain frustrate you. That’s why at Tillery Innovations, we offer quality running and grozing pliers (including the narrow kind!) that are designed to help beginners build confidence and precision. With the right tools and a little practice, you’ll go from cracking glass in frustration to cracking glass like a pro.

Now go score, snap, and sparkle—just don’t forget your safety glasses.