Posts in TIPS AND TRICKS
7 COMMON GRINDING AND POLISHING MISTAKES YOU COULD BE MAKING

Surface Preparation is a competitive industry and the ability to achieve quality outcomes are essential for getting noticed. This blog will touch on the 7 most common grinding and polishing mistakes and why it’s important to correct them.

MISTAKE 1: SELECTING THE INCORRECT BOND FOR THE CONCRETE YOU’RE WORKING WITH.

Once you understand how metal bond diamond tooling works, you can use the general rule of thumb when selecting the tooling for your job.

The “rule of thumb” is:  soft concrete requires hard bond diamonds and hard concrete needs soft bond diamonds;

  1. Soft Concrete = Hard Bond Diamonds

  2. Medium Concrete = Medium Bond Diamonds

  3. Hard Concrete = Soft Bond Diamonds

  4. Very Hard Concrete = Extra Soft Diamonds

A major mistake contractors make, is selecting the incorrect bond for the concrete hardness and doing so will result in two outcomes…

  1. The diamonds do not cut- often due to heating up and glazing over. (This happens mostly on hard concrete.)

  2. You will wear out your tooling prematurely

Either way you end up wasting your time, and money, and your results will suffer.

MISTAKE 2: RUNNING THE GRINDER UNNECESSARILY FAST

A common mistake an operator can make when feeling under pressure, is running the grinder at an unnecessarily fast speed. We tend to see this happening when an operator wants a faster production rate and will turn up the speed of the grinder in efforts to accomplish more in less time. However, this increased speed can overheat and “glaze over” your diamonds (especially on hard concrete) which prevents them from cutting properly, or at all (as mentioned earlier).

To give you an example, our Predator grinder/polishers run a maxim drum speed of 1,200 rpm when dial set at 10 (full power). Although it can go 1,200 rpm if need be, generally it’s recommended to set the dial around 4.5-5.5 which runs the drum at approximately 600rpm. An operator can then adjust up a little or down a little to get the best performance.

Finding the right speed is important but speed alone doesn't necessarily equate to better production rates. Ultimately, greater downward pressure = faster grinding

There are two ways of achieving this: A heavier machine will obviously give more head pressure but, so do different diamond options;

  1. Single Round

  2. Double Round

  3. Single Rectangle

  4. Double Rectangle

If you are operating a smaller machine (like the P-1800 & P-2400 for example) a Single Rectangle or single round will give more down pressure because you have double the square inch pressure, compared to a double round or rectangle; allowing it to cut faster. Opposite is true of the larger machines where a double segment will offer a better performance because it is grinding a larger space at one time.

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MISTAKE 3: GOING FOR THE LOWEST PRICE DIAMONDS… SIMPLY BECAUSE OF THE PRICE

Although sometimes price isn’t always an indicator of quality (or lack thereof) when it comes to diamond tooling, it’s important to make sure that price isn't your only criteria of consideration for purchase. Poor quality diamonds wear faster, and inconsistently. They can scratch floors, and generally perform poorly, usually with limited or no support from the vendor. Buy from a trusted vendor willing to stand behind their products. This will save you time and money in the long run.

MISTAKE 4: NOT INSPECTING YOUR FLOOR BEFORE STARTING

A metal bond diamond will grind and polish almost anything from steel, brass, glass, etc. AS LONG AS, the material is not “above grade” (raised above the floor surface). Make sure you inspect the floors for anything above grade and either cut off, hand grind to level, or smack with a hammer to knock below grade. Once you’ve eliminated the above grade issues, you can grind it along with the concrete resulting an interesting detail that adds to the personality of the floor. If you DO NOT inspect the floor and deal with the parts above grade before you begin grinding, you will most likely knock your diamond segment off and can do a lot of damage to your machine. 

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MISTAKE 5: NOT UNDERSTANDING THE PROCESS NEEDED FOR THE DESIRED OUTCOME

Here are a couple questions and cautions for determining what your starting diamond will be…

  • What finish am I trying to achieve? i.e.  Cream Polish? Salt & Pepper Finish? Heavy Aggregate exposure?

  • What is on the floor now that must be removed before the polishing process can begin? Like epoxy coatings, VCT, Ceramic Tile etc.

Here are some important things to be aware of…

  1. Most polishing will start with a 40G metal bond diamond to expose the salt & Pepper or aggregate.

    1. If doing a cream polish you will almost NEVER start with a metal bond diamond as it will remove the cream, and once it’s gone… it’s gone forever.

    2. If removing material like an epoxy flooring before the polishing process do not succumb to the temptation to use a more aggressive diamond like a PCD as it will make deep scratches that are extremely difficult, if not impossible, to remove.

    3. When you’re not sure what diamond to start with, err on the side of caution and start with a less aggressive diamond, because you can always drop back to a more aggressive diamond, if need be.

MISTAKE 6: NOT REMOVING STUBBORN SCRATCHES IMMEDIATELY

When polishing a floor, you must keep an eye on the finish you’re producing as you go. If you see faint scratches starting to appear you must remove them immediately, rather than “hope” the problem will cure itself… because it won’t - it will only continue to manifest as you polish up the floor.

For instance, if you are running a 100G resin bond diamond and you start to see scratches, do not think your next step, with 200G resins, will remove them. You must remove them with the 100G or if necessary fall back to a more aggressive diamond like a 50G or 30G resin before you move onto the next step.

To reiterate: Remove the problem scratches as soon as you see them. Do NOT leave them and hope they go away… because they won’t and your results will suffer because of it.

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MISTAKE 7: NOT PROPERLY MANAGING CUSTOMER EXPECTATIONS

This may not seem like something that is overly important but in reality it’s incredibly important. Every customer has a vision of how they want the floor to look upon completion- sometimes it’s achievable but not always, so it is important to effectively manage customer expectations. This is often what contractors new to polishing and grinding find most difficult.

It is so important to properly educate your customer on what is a reasonable expectation for their floor, because every floor is different and has its own “personality” so to speak.

Here are some potential topics that should be covered before work begins…

  1. If removing VCT before polishing, you will most likely see a “ghost shadow” of the VCT that will NEVER go away no matter how much grinding you do- and you won’t see it until the polishing part of the job.

  2. Be aware of hidden imperfections like spalling, trenches etc.

  3. Never promise a consistent monolithic floor (all salt & pepper or all cream finish) promise the opposite, because you will have inconsistencies, cracks, spalling and the like. It is simply the personality of the floor and that is what polished concrete is. If the end user wants a more consistent floor finish, then possibly an overlayment will be required to get the floor to the desired finish..

Again, if you're ever uncertain and need some clarification it is important to reach out to the dealer or manufacturer and get their advice on how to move forward. 

Original article written by Randy Wheelis.

KEY COMPACTION TIPS

In any type of construction, it’s often your base or foundation that determines the long-lasting success of your project. The more compact and dense your building base is, the more likely it will be stable and secure in the future. Compaction is the process of compressing various ground materials to reach a certain level of hardness and density. Two of the most common machines used in construction for compaction are Rammers and Plate Compactors.

Rammers compress the ground materials by striking the surface with weight and force while Plate Compactors use consistent weight and vibration to compress the base material. Both of these machines achieve the same results but use different methods to achieve it.

Regardless of the machine you chose to get the job done there are two important factors to consider to ensure the job is done right….

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UNDERSTAND AND ADHERE TO THE CORRECT COMPACTION SPECIFICATIONS TO THE PROJECT.

All projects have a specific ground compaction requirement based on the project being built over the base surface. It’s important to know what the compaction specifications you are trying to achieve as directed by the project engineer or project manager. All engineers will have a specification of compaction based on the project they are building.

To determine the required compaction specification a Standard Proctor Density Testis often requested by the engineer. This process is done in the lab to test the site soil density by applying various moisture content amounts to the soil and applying a controlled compaction method to determine the optimum compaction specification.  When the optimum compaction rate is determined a nuclear gauge is used on the site after compaction to confirm the soil base meets specifications.

A key factor in compaction is to remember that not all soil types are the same and can vary greatly from jobsite to jobsite. Soil differences like clay, sand, silt and gravel (or any combination thereof) has an impact on achieving the desired specification. If you fail to achieve your required compaction specification, or if you compact beyond the optimum compaction rate, you can decrease compaction and increase project risk on the site. A standard Protor Density Test provides the engineer the required compaction information, and the nuclear gage measures the results on the site to ensure the compaction meets specifications.

For projects that don’t require a specific engineer specification, a general ‘rule of thumb’ spec. for compaction will often require a base of 1,000 lbs of compaction for every inch of material. This number will vary depending on the project being built over the surface, and the base mixture. If you are going to ensure a successful and long lasting project always know your base mixture and follow the required compaction specification for the project.

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USE THE CORRECT TOOL TO GET THE JOB DONE EFFICIENTLY 

Generally speaking either a rammer or plate compactor are capable of compacting the same types of material, but typically Rammers work better on cohesive material (materials that compress like clay) and Plate compactors are more effective on granular materials (like crushed stone). Both of these types of materials compact well, but have different ways of compacting. Granular materials ‘interlock’ as they compact, cohesive materials compress as they compact.

Another factor in choosing the right tool often has to do with ease of use and accessibility. Rammers by nature are smaller and more light weight and achieve compaction by repeatedly ‘hitting’ the surface with the ‘shoe’ of the machine to compact. They are easy to get into tight areas like trenches and easy to transport onto jobsites using simple pickup trucks or small transport vehicles. Plate compactors are often used for larger wide open areas that can be accessed a little more easier. These units (depending on their size) are heavier and are often transported on equipment style trailers or trucks.

Compaction is a simple procedure but its important to know what compaction specification you are trying to achieve – testing for optimum compaction and pairing the right type of compaction equipment with the project job site to make sure things go smoothly, easily and to spec.

Original Article Written by Mike Huggins.