When to use a hard or soft bond diamond

“Without the proper knowledge or diamonds this can ruin a reputation or even worse ruin a company.”

By: Jason Root

With the concrete polishing industry continuously expanding into new markets and increasing square footage being quoted and polished every month, it is more important than ever to understand the diamond tooling available.  With so many different shapes, sizes, quality levels, bonds and ways to attach these diamonds to your machine it is becoming especially difficult to decide what diamond is right for the job you are quoting or polishing.  With so many construction supply companies and online stores now selling these diamonds, it is easy to find diamond tooling for concrete polishing these days; however, it is more difficult to find the right diamond for the best production and life.

Machine Size

Head pressure plays a very important role in achieving the proper grind

First, let’s talk about the machine being used and the down force or head pressure of the machine you are using.  Typically the more head pressure your machine has the more diamond surface area you should have underneath your machine.  In most situations, you would not want to use the same diamond under a 150 lb 110V machine as you would under a 1100 pound 25 horsepower machine.  Basically, the more down force per square millimeter of diamond you have the more aggressive your grind will be; while aggressiveness/production is good you can often wear diamond very quickly with too much down force.  When polishing with larger machines a higher quality diamond will be worth the extra expense as cheaper diamonds will tend to glaze over or wear very quickly.  Many times, contacting your equipment manufacturer for recommended diamond surface area and quality level is a great first step.

Another very important part of selecting the right diamond tool is to understand the concrete that you are grinding or quoting.  The more concrete you grind the more you learn and the easier it is to “read” a floor.  From hard trowel floors with curing agents and sealers to broom finished floors, or noticing white chalky moisture coming through, these are all visual signs that will tell you the floor may be abnormally soft or hard.  I would estimate about 80% of concrete polishing or grinding jobs fall into the category of “normal”.  In this case a medium bond diamond should perform and last long enough for you to make a profit on your diamond investment.  It is the other 20% of the floors out there that can sometimes leave even experienced contractors scratching their heads and, even worse, losing money.  Knowing the PSI of the floor and the aggregate type can be helpful (4,000 – 6,000 is normal); a simple Moh’s hardness scratch test (4 – 7 is normal) will also usually show if something is abnormal.  There is a sense of panic and confusion that can set in when a contractor is under the gun to finish a polishing job and his diamonds suddenly completely stop cutting or are wearing out at an alarming rate.  Without the proper knowledge or diamonds this can ruin a reputation or even worse ruin a company.  The luxury of running a test sample with your diamonds and your machine before the job (or even before the quote) can be very useful.

Diamonds: They are now a man’s best friend

Understanding how a diamond works will help you choose the right diamond with the right characteristics to get the most out of your investment.  The two major components of a diamond grinding segment are the matrix and the synthetic diamond crystals.  The matrix is the material that holds the diamond particles in place until they wear away; this is typically a metal or resin bond.  A wide range of materials can make a bond harder or softer depending on the application.  The exposed diamonds on the surface of each segment do the actual cutting, using abrasive action to slice through material as it rotates.  The diamonds at the surface become dull through use and (when the bond is right for the application) the matrix around the dull diamonds begins to shed away releasing the worn diamond crystals to expose new, sharp diamonds that are embedded within the matrix.  The most important fact here is to know the matrix will control how quickly a segment is going to wear.

Along with different bonds, diamond grinding segments come in many different patterns as well

Why have my diamonds stopped cutting?  Everything was going great for the first 20 – 30 minutes then my production started to decline and now the diamonds are not grinding at all.  The majority of the time this is caused by very hard concrete.  A hard trowel, curing agent, sealer or just plain hard concrete can heat up the diamonds, round off the diamond cutting edges and cause major headaches as production can slow to a crawl.  This is called “glazing”, and the first thing you want to try when your diamonds are glazing is a softer bond diamond.  Although it can be expensive, an investment worth considering is stocking hard and soft bond diamonds for the 15-20% of the jobs that are considered abnormal.  This can help you avoid losing a day of work and rushing overnight shipments of these bonds to your jobsite.  To reopen a glazed diamond you can add a little water or throw some sand under the machine; this can cause an abrasive reaction that can sometimes reopen the diamond segments and expose new, sharp diamond.

“Broom finish, shaved concrete, sandy looking concrete all can tear through your matrix and most of your sharp diamonds will end up in the dust collector.”

On the other hand, you can be getting all the production in the world when suddenly you tilt the machine back and find your $1000 set of diamonds are completely gone and you have only done 500 sq/ft!  This is typically the case of extremely soft concrete (or sometimes cheap diamond quality).  You may be able to run water with these diamonds (something doesn’t look right here—not sure if it should be these, not these, diamonds) and slow the wear slightly but the right thing to do here is get a harder bond set of diamonds.  Broom finish, shaved concrete, sandy looking concrete all can tear through your matrix and most of your sharp diamonds will end up in the dust collector.  A bond made up of harder metals will slow the release of the diamonds and will allow good production with extended life.  This is also a situation where adding more diamond surface area will also help to gain more life.

With all this being said, purchase your diamonds from someone that has experience with your job applications and someone you can call on when you have a problem.  Buying diamonds from an EBay type outlet might seem tempting at times because of the price but will they be there for you if you have a problem?  If you are new to the industry, ask around and get referred to a quality diamonds supplier that can work with you and your job directly.  Track the wear and production of your diamonds as close as possible so you have a realistic guideline as to what you should expect from the floors in your area.  This exciting industry is still very new so keep your eyes open for new products that will increase production and profit.

Jason Root has over 15 years experience in the diamond tool industry basically growing up in the industry at Sawtec, Blastrac, U.S. Saws and Blades and now Syntec Diamond Tools.  He has helped develop several patented segment designs and enjoys the challenge of testing and creating new diamond tools that help evolve this great industry.
Email jasonr@syntecsolution.com

Respirators are an extremely important part in maintaining a healthy work environment.  When polishing concrete, health and safety should be a top priority on every site.  This program will help you and your company determine the safest method of protection for the specific application.  The main site can be found here.  This easy-to-use program will walk you through the proper Respirator Selection Process as well as help you Develop a Change Schedule