Monthly Archives: March 2014

From the Archives: How Do Grinding Wheels Work?

SCIENCE! and Technology Articles on Desert Diamond Industries' Blog

This article is from our archives. Let us know in the comments section if you found it helpful or interesting!

Our article on diamond blades drew a lot of interest, so we’re going to follow it up today with a discussion on grinding wheels.

Before we start talking about grinding wheels, though, we should first pin down what we mean by “grinding wheels”. After all, there’s grinding wheels, grinding stones, grinding cups, grinding points, and the list goes on. Therefore, to narrow our discussion, we’re going to confine this article to straight wheels – that is, flat grinding wheels that grind with their faces.

How Grinding Wheels Work: Grinding wheels are similar to the diamond blades that we talked about earlier. They both have some kind of hard, abrasive grit that’s usually held in some kind of bond. The grit scrapes chips out of the material that you’re grinding or cutting, while the bond wears away to shed worn grit and expose fresh, sharp grit buried deeper in the wheel or blade.

Which Grinding Wheel You Should Use: You need to consider three things when choosing a grinding wheel: abrasive, bond, and grit size.

Abrasive: You should match the abrasive in your grinding wheel to the material that you’re grinding. Here’s some of the most common abrasives:

  • Aluminum Oxide: Designed for grinding carbon, stainless, and high-speed steel, malleable and wrought iron, aluminum, and bronze.
  • Silicon Carbide: Designed for grinding cast, gray, and chilled iron, non-ferrous metals like soft bronze, brass, and aluminum, and non-metallic materials like concrete, brick, marble, stone, rubber, and glass.
  • Zirconia Alumina: Designed for high stock removal of steel and steel alloys. Resists higher temperatures and pressures.
  • Ceramic Aluminum Oxide: Designed for precision grinding of tough materials like stainless steel, titanium, and high-nickel alloys.
  • Superabrasives: Extremely hard and expensive materials like diamond or cubic boron nitride. Designed for grinding very hard materials that may defeat other abrasives.

Bond: Most grinding wheels have their abrasive grit bonded either directly to a metal or rubber disc or within vitrified or organic resin bonds. However, what matters isn’t the bond itself, but its hardness.

Grinding wheel bonds are similar to diamond blade bonds: harder bonds last longer, while softer bonds grind faster and with less pressure. You can tell the hardness of your wheel’s bond by a single-letter code on the wheel, with A as the softest and Z the hardest.

Grit Size: This is a big factor in a grinding wheel’s speed and finish. Grit size works pretty much the same for grinding wheels as it does for sandpaper: larger, lower grit grinds faster and and leaves a coarser finish, while smaller, higher grit grinds slower and leaves a smoother finish.

Dangers of Grinding Wheels: Remember, grinding wheels are designed to grab onto things and scrape chips out them while spinning insanely fast, and they don’t care what they grab onto or where they throw those chips. Therefore, you should always take precautions when grinding, including:

  • Wearing personal protective equipment like safety glasses and gloves.
  • Making sure your grinding machine’s guards are installed and in place.
  • Taking off or tying back loose clothes.

In addition, certain grinding wheels pose their own risks, including shattering and emitting hazardous silicon carbide fibers.

Shattering: Vitrified and resin grinding wheels fly apart if they’re nicked, damaged, or run at too high a speed. These accidents produce shrapnel that can injure or kill the grinder operator.

To prevent shattering, you should check these kinds of grinding wheels for cracks and large nicks before and after using them. The Oklahoma State Regents for Higher Education recommend the “ring test” – that is, lightly tapping the edge of a vitrified or resin wheel with a non-metallic object before starting it up. If you hear a dull thud instead of a metallic ping during this test, throw out the wheel and get a replacement.

You can also help prevent grinding wheel damage by:

  • Carrying the grinding wheel to your grinder instead of rolling it, no matter how big it is.
  • Running it within its recommended RPM.
  • Grinding with only its face instead of its edge.

OSHA also recommends standing off to one side when you start up your grinder and then letting it run for a full minute, just in case your grinding wheel does shatter.

Silicon Carbide Fibers: Grinding wheels with silicon carbide abrasive pose a special hazard: emitting silicon carbide fibers during grinding that can lodge in your lungs. Long-term exposure to these fibers has been linked to increased mortality from asthma, emphysema, chronic bronchitis, pneumoconiosis, and lung cancer. We therefore recommend that you wear a respirator whenever you use or are around silicon carbide grinding wheels.

Of course, you can avoid shattering wheels and inhaling silicon carbide fibers by using a metal grinding wheel instead of a vitrified or resin one, like the Safety Blade Grinder/Cutter. The Safety Blade Grinder/Cutter is made of solid steel, so it won’t shatter or break apart under normal use. In addition, its thick coat of diamonds grinds a wide variety of materials, including iron, steel, non-ferrous metals, high-nickel alloys, welds and welding slag, concrete, asphalt, brick, block, stone, you name it.

Works Cited

“Abrasive Wheel Grinder Safety.” System Safety, Health and Environment Resource Center. Oklahoma State Regents for Higher Education, n.d. Web. 28 Aug. 2013. < http://www.okhighered.org/ssherc/newsletters/osrhe/abrasive-wheel-grinder-safety.html >.

“Grinding Wheel.” Wikipedia. Wikipedia, 9 Apr. 2013. Web. 28 Aug. 2013. < http://en.wikipedia.org/wiki/Grinding_wheel >.

“Grinding Wheel and Abrasives Basics.” Georgia Grinding Wheel. Georgia Grinding Wheel, 25 Nov. 2008. Web. 28 Aug. 2013. < http://www.georgiagrindingwheel.com/grindingwheels_basics.htm >.

“Hand and Power Tools – Hazard Recognition.”  Occupational Safety and Health Administration. Occupational Safety and Health Administration, May 1996. Web. 28 Aug. 2013. < https://www.osha.gov/doc/outreachtraining/htmlfiles/tools.html >.

“How a Grinding Wheel Works.” Flexovit Abrasive Products. Flexovit Abrasive Products. Web. 28 Aug. 2013. < http://www.flexovitabrasives.com/education/performance/how-a-grinding-wheel-works/ >.

“How Do Diamond Blades Work?” Desert Diamond Industries’ Blog. Desert Diamond Industries, 27 Aug. 2013. Web. 28 Aug. 2013. < https://desertdiamondindustries.wordpress.com/2013/08/27/how-do-diamond-blades-work/ >.

Sullivan, Joe. “Choosing The Right Grinding Wheel.” Modern Machine Shop. Gardner Business Media, 15 Dec. 2000. Web. 28 Aug. 2013. < http://www.mmsonline.com/articles/choosing-the-right-grinding-wheel >.

“Q. What’s the Difference between Abrasive Wheels and Blades and Diamond Grinders and Blades?” Desert Diamond Industries Blog. Desert Diamond Industries, 2012. Web. 28 Aug. 2013. < https://desertdiamondindustries.wordpress.com/2013/11/13/q-whats-the-difference-between-abrasive-wheels-and-blades-and-diamond-grinders-and-blades/ >.

How to Size Up Peaked Roofs for Ventilation, by Fire Engineering

Sizing Up Peaked Roofs for Ventilation, by Fire Engineering

How can you tell which structure fires need roof ventilation and which ones don’t or are too dangerous for it? Jeff Johnson of the Kansas City, MO Fire Department has the answer in his Fire Engineering article.

One thing to look at is the roof, he says. The roof can give you all kinds of information about its safety and the fire underneath it, but only if you know how to read it. We’ve summed up the most important indicators in Johnson’s article in this bullet list.

  • Smoke: Smoke rising high into the sky indicates high heat from a more developed fire and greater danger to firefighters and occupants, while smoke hanging around the eaves could indicate less heat or a fire that hasn’t made it to the upper floors.
  • Roofing Materials: Asphalt shingles can indicate lightweight truss construction and can hide the signs of impending roof failure. Heavier materials like slate or clay tiles, on the other hand, are probably built on top of more solidly-built roofs and will need more personnel and effort to ventilate. Both can collapse at any time, so don’t take your eyes off the roof for a second, no matter what it’s made of.
  • Dormers: A useful roofing feature for firefighters, dormers give you a look into the attic and can be used for ventilation.
  • Skylights: Another useful roofing feature, as we’ve noted here before, are skylights. They can tell you if the fire’s worked its way up into the roof and, with a little work, can also be used for ventilation.
  • Roof Vents: Both fixed and turbine vents vent heat from attics. Turbine vents are especially useful during a size-up because they spin faster the hotter the attic gets, at least in windless conditions.
  • Other Roof Features: Roof features and equipment can warn you of roof collapses if you know how to read them. Keep an eye out for rain guards and flashings raised above the roof line, melting tar, or the chimney and roof pulling away from each other. These are signs for you to get your guys off the roof and maybe out of the structure.
  • Fire District: Probably the best way to know how to vent roofs is to know what kinds of roofs are in your district! Visit construction sites, learn about existing buildings, build props and mock-ups of them, and then train, train, train.

Read Johnson’s full article at Fire Engineering.

Fire Engineering, Jeff Johnson, “Size-Up: Reading the Pitched Roof

Want to Find Out More about Desert Diamond Industries?

Ever wonder why we make vacuum-brazed diamond tools like the Ductile Iron Safety Blade and Fire Rescue Safety Blade? Or about the people behind those tools?

Well, wonder know more! We’ve updated the About Us page on our website! Check it out now!

Safe Dry-Cutting with Diamond Blades

Dry Cutting Tips for Diamond BladesDespite what you may have heard, you don’t always need water when cutting with a diamond blade! Dry-cutting even has advantages over wet-cutting: you don’t need to clean up slurry after you’re done, you can cut in places without reliable water sources, and you’ll tend to get cleaner, crisper cuts.

That being said, you can’t just slap any old blade on your saw and go to town without knowing what you’re doing.

First of all, you need to use a blade that’s designed for dry-cutting (may we suggest our Ductile Iron Safety Blade?). That’s because the water used in wet-cutting cools the blade. Cut without this cooling water, and you’ll quickly destroy a wet-cutting blade. Even worse, the heat will weaken the welds holding the cutting segments onto your blade, and if those segments break off during cutting, they may injure or kill you.

Second, you need to cut differently when dry-cutting. That’s because dry-cutting blades are cooled by air while cutting, and that air can’t get to the blade if you bury it deep in a cut. To get around this, you should step-cut – that is, cut an inch or so deep at a time – and periodically take the blade out of the cut to let it free-run and cool down.

Third, you need to wear a respirator when dry-cutting, especially if you cut concrete, brick, block, and stone. That’s because the water used in wet-cutting is one of the best ways to reduce dust while cutting. Without this water, you’ll inhale more silica dust, which can lead to lung diseases like silicosis, pneumoconiosis, and lung cancer.

In short, we’re not saying that you shouldn’t dry-cut. If you do, though, make sure that you have the right blade, the right cutting technique, and the right safety equipment for the job.