T27 vs. T29 Flap Discs: Which to Use?

T27 vs. T29 Flap Discs: Which to Use?

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If you are planning to work on metal, then one tool that you might have use for is a flap disc. To be exact, flap discs are attachments for grinding tools. These are used to grind and shape metal. That said, there are various types of flap discs out there, and each one has a specific use.

Today, we want to compare the two most com T27 and T29 flap discs. Let’s figure out what the differences between them are, and which one is ideal for what sort of purpose.

Flap Discs: The Basics

The flap disc is a very special type of abrasive wheel that is used with both angle grinders and die grinders. These consist of a backing plate to which overlapping pieces of material with abrasives are attached. It kind of looks like overlapping pieces of sandpaper attached to a circular disk with a hole in the middle.

Unlike normal grinding wheels that are totally flat, flap discs are made out of various flaps of abrasive materials that are layered over each other. These flap discs come in various shapes, grit levels, and are made with a variety of materials.

While there are various materials, grits, and sizes of flap discs, one of the most important distinctions between them is the angle that they feature. The “T” rating refers to the angle of the flap disc, and of course, today we are here to compare the T27 and T29 angle flap discs.

For the record, flap discs are a go-to abrasive attachment, and they are used to remove paint from metal, surface blending, contour work, smoothing, and edging metal. Simply put, flap discs are very special kinds of grinding wheels.

Flap Disc in Use

Similarities of T27 and T29 Flap Discs

Let’s first determine what the similarities between T27 and T29 flap discs are.

1. They’re Both Used for Metal

One of the most basic similarities here is that both of these types of flap discs are designed to be used on metal. Although they excel at slightly different jobs, both the T27 and T29 flap discs are designed for removing paint from metal, shaping and finishing metal, and removing material.

2. They’re Both Designed for Grinding Tools

Another basic similarity that both the T27 and T29 flap discs share is that they’re made to be used with specific grinding tools. Remember that flap discs are accessories or attachments, not tools in themselves. Depending on the size and type, they can be used with both angle grinders and die grinders.

3. They’re Both Alternatives to Traditional Grinding Discs

Normal grinding discs are fine for basic and quick work. However, due to the special overlapping flap design of both the T27 and T29 flap discs, they make for good alternatives to grinding wheels when both speed and precision are called for. Doing precision work is easier done with a flap disc than a normal grinding wheel.

4. They Both Feature the Same Construction Type

Both the T27 and the T29 flap disc feature overlapping layers of materials that create these flaps. Yes, they have slightly different shapes, but the basic construction type is still the same.

5. They Can Both Be Various Sizes & Materials

The other similarity worth noting is that these flap discs come in a variety of sizes to suit various sizes of grinders (and for specific jobs). They can also be made out of a fairly wide variety of abrasive materials.

T27 Flap Discs

Differences Between T27 and T29 Flap Discs

Now that we know what is similar about T27 and T29 flap discs, let’s figure out what makes them different.

1. Shape

One of the most basic differences between these two flap discs is the shape that they have. The T27 flap disc has a completely flat face design with a 0-degree angle. In this sense, it looks more like a traditional flat grinding wheel. On the other hand, the T29 has a slightly angled face. Although it doesn’t come to a point, it does have a slightly conical shape.

2. Best Grinding Angle

When using a T27 flap disc, it is best held to the material being grinded at an angle between 0 and 15 degrees. On the other hand, a T29 flap disc is best held to the metal being grinded at an angle between 15 and 25 degrees.

3. Primary Purpose

Perhaps the biggest difference here is what both of these flap discs excel at. The T27 is best used for blending surfaces and for smoothing them. This type of flap disc is also best used for sanding flat surfaces. On the other hand, the T29 flap disc is best used for shaping and contouring metal surfaces, and for work on uneven metal surfaces.

4. Ability to Grind Material Away

While a T27 can grind material away from a metal surface, the T29, due to its angle, is better for aggressive material removal and grinding.

T29 Flap Disc

T27 vs. T29 Flap Disc: Which One Should You Use?

If you are working on a flat surface, blending surfaces, and smoothing out a finish, then a T27 is the way to go.

However, if you are looking to quickly grind away material, are working on an uneven surface, or want to shape contours and edges, then the T29 is the way to go.


Now that you know what the differences between T27 and T29 flap discs are, you can make an informed choice between them.