Hard, Soft, and In-Between: A Guide to Diamond Segments and Bond Types

If you’ve ever seen your diamond segments "glaze over" and stop cutting, or watched a brand-new set of shoes disappear after only 500 square feet, you’ve experienced a bond mismatch.

In the world of concrete grinding, the diamond isn’t the only thing doing the work—the metal "bond" holding those diamonds is just as important. Here is everything you need to know to choose the right setup for your next job.

1. How Diamond Segments Actually Work

It’s a common misconception that the metal bond does the grinding. In reality, the metal matrix is designed to wear away at a controlled rate. As the metal wears down, it exposes new, sharp diamond grits.

• Too hard of a bond: The metal doesn't wear down, the diamonds get dull (glaze), and the tool stops cutting.
• Too soft of a bond: The metal wears away too fast, dropping perfectly good diamonds on the floor before they’ve done their job.

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2. Matching Bond Hardness to Concrete PSI

The golden rule of grinding is opposites attract. You want to use a soft bond on hard concrete and a hard bond on soft concrete.

Concrete Type	PSI Range	Recommended Bond	Why?
Very Hard	6,000+ PSI	Extra Soft	Needs a "weak" metal matrix to constantly expose fresh diamonds against the dense surface.
Hard	4,000 – 6,000 PSI	Soft	Provides a balance of durability and cutting speed.
Medium	3,000 – 4,000 PSI	Medium	The "standard" bond for most residential slabs and general-purpose grinding.
Soft/Abrasive	< 3,000 PSI	Hard	Prevents the abrasive sand in the concrete from eating the tool alive.

 

3. Understanding Segment Shapes

The shape of the segment on your grinding shoe affects the "head pressure" and the scratch pattern left behind.

• Double Buttons/Rounds: Great for lighter machines. The smaller surface area increases the pressure per square inch, helping the diamonds "bite" into the floor.
• Rectangular/Bar Segments: Ideal for heavier machines. They provide a wider footprint and longer life, making them the workhorse for large commercial areas.
• Arrow Segments: Designed with sharp leading edges to "plow" through thick coatings like glue, epoxy, or thin-set while grinding the concrete underneath.
• PCD's: Designed to act as a scraper to remove thicker coatings like thin-set or mortars. These are not meant for grinding concrete.

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4. Grit Sizes: When to Use What

Grit refers to the size of the diamond particles embedded in the bond.

• 16/20 Grit: Aggressive removal of coatings and heavy "cream" layers. Leaves deep scratches.
• 30/40 Grit: The standard starting point for most grinding projects.
• 60/80 Grit: Used for removing scratches from the previous steps and preparing the floor for thin-film coatings.
• 120/150 Grit: The final metal-bond step before transitioning to resin-bond polishing pads.

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Pro Tip: The "Scratch Test"

Before you start a large job, use a Mohs Hardness Pick Set. If you find the concrete is a 7 or 8 on the Mohs scale, reach for your Extra Soft Bond tools. If it’s a 3 or 4, stick with a Hard Bond to save yourself hundreds of dollars in tool wear.

Need help picking the right tooling? Check out our Grinder Starter Packages or contact the team at Iron Horse for a recommendation based on your machine specs!