Monday, 21 March 2016

Metal Treatment. Part 1

This article contains information about marking of abrasive grinding disks, some theory of metal cutting treatment and recommendations for choosing wheels for a certain type of work.

Grinding discs are metal treating tools for rough and clean treatment of metal items or other relatively hard materials. Besides those grinding wheels, there are tools used for hand and stationary machines: blocks, oilstones, segments etc.

In spite of tools and materials for polishing, grinding tools have cutting edge of abrasive crystals. Cutting edge of the wheel is characterized by durability, strike viscosity, height and flexibility. Application of tools depends on hardness of abrasive material. The harder the material is, the wider the range of treated materials is.

While using too soft abrasive for hard materials (talc or emery for hard steel or superalloyed steel) there is high wear of the disk. After this process the applied surface is with high cleanness of treatment, however, the grinding is not precise.

If using tools with too hard abrasive grain for treatment of soft materials (for example, white aluminum oxide or boron carbide for copper or aluminum) the treatment is carried out well, but the disk is jammed with cutting waste.

That is why some users try to use wheels with weak bond (this way is not economical due to high waste of expensive abrasive) or to clean the result with a “diamond” (this way is not enhance economy as well). A “diamond” is a tool for wheel correction, i.e. for deleting curves from wheel surface and deletion of abrasive layer jammed with cutting waste. A classical diamond is a small block of tiny crumb of technical (usually synthetic) diamonds with tungsten bond, aluminum and copper. For a stable fixing of block there is a metal handle.

Thursday, 21 January 2016

Abrasive Cutting Coefficient. What It Is and How It Is Calculated

One of the main characteristics of the cutting of abrasive wheels to determine their quality is such parameter as the abrasive cutting coefficient, which is often called the coefficient of grinding. It defines the ratio of the area of the cut to the size of the blank area of the worn when cutting. Coefficient helps to determine the wear resistance of cutting tools for different materials. The same cut-off wheel can variously show it wear resistance and coefficient of cutting depending on use in a stationary equipment or on the angle grinding machine, which is influenced by an additional effect of vibration.
The coefficient K while using an abrasive cutting wheel to a value equal to 0.75 of the initial diameter can be determined from the following formula:

K = 4*SЗ*n / π*(Dk2  Dн2)

Where: n – number of cuts; SЗ – area of cutting in sq. cm; Dн и Dk – diameters before and after cutting.
Another important parameter of an abrasive wheel is operating speed, measured in m/s, which is always specified on the label. Exceeding it is not allowed. It can lead to the destruction of the instrument or other undesirable consequences.

Wednesday, 16 December 2015

5 Advantages of Abrasive Discs

Here I`d like to write about advantages of resin bonded abrasive discs.
  1. Cheap price. It is the main criteria for buying for household. If you do not operate cutting works professionally, abrasive cutting and grinding discs can become the best solution. Especially when it comes to cutting stone.
  2. Abrasive discs do not need any type of cooling. No water cooling is used.
  3. Abrasive wheels are always sharp, no matter how narrow diameter is left. The sharpness will remain the same.
  4. They are always available at any DIY store. You can buy abrasive discs almost at every market. Besides there are many websites offering abrasive cutting and grinding discs.
  5. Large variety of applications allows to choose the most suitable disc for an exact work.
Here you can find more about abrasive discs.

Friday, 4 December 2015

Thin Abrasive Discs

Nowadays the masters working with angle grinders use the phrase "thin circles." They designated a relatively new category in the market abrasive tools - cutting wheels small thickness (about 1 – 1,2 mm).
A user of thin discs gets the following advantages:

  • A thinner discs provides a better elasticity. It means that under big pressure it will not break off, unlike 2,5 mm disc. 
  • Thin discs are energy efficient. Using them an angle grinder consumes less power. 
  • Cutting process is faster meanwhile cutting coefficient is higher. The whole cut is even, not curved. 
  • There is another remarkable feature. Only prominent producers can make real size of 1,0 mm discs. For example, Klingspor, Tyrolit, NovoAbrasive. For this thickness it is harder to find a counterfeit Chinese product. 

Very often operators underestimate efficiency of dispensable instrument, such as cutting discs. Nevertheless, qualitative discs can make a crucial effect in work.

Tuesday, 17 November 2015

Functional Protection for Angle Grinders

Convenience and safety for working with an instrument is provided by functional features of the tool. In this article I`ll give you some info about some of important features.

Soft start
Those angle grinders having soft start option are less affected by short critical overload at starting time. Especially soft start is needed for powerful angle grinders having a large weight of inner parts and abrasive wheel mounted. In case of present soft start function the grinder starts working smoothly, not shaking in hands and motor brushes are not suffered by high current steps.

Rotation settings
Rotation setting system enables to find out rotation speed for a certain need: i.e. cutting process, grinding, deburring etc. These are additional facilities provided for optimization of work modes of the instrument.

Stabilization of rotation
Revolution stabilizing system helps to work with large massive surface.

Protection from disc jamming
If the abrasive disc is jammed during the cutting process, this is very dangerous and may lead to serious injury. The instrument is briskly pulled out with unknown circumstances. To avoid that the professional angle grinder should be equipped with jamming protection system. Here in case of jam the tool gets turned off immediately.
Angle grinder cutting

Secondary start fuse
In case when the power is off (for instance, someone pulled out a plug) and the work starts again, the angle grinder can be protected by spontaneous secondary start.

Brush protection
Some good quality angle grinder producers install a special system protecting motor brushes from voltage loss. This may avoid burning relay contact.

Balancing system
This feature helps to reduce vibration of the tool affecting work quality.

Dust protection

Especially needed when cutting stone, masonry, brickwork, concrete. You should ask about that issue while choosing an angle grinder for dusty work.

So be assured that those fatures are included into the tool you plan to buy!

Thursday, 5 November 2015

Application of Abrasive Discs. Recommendations about Disc Thickness

Angle grinder disc

In this article I will give you a couple of tip about application of abrasive discs.

As we have already discussed on the pages of this blog, abrasive discs can be of two types: cutting and grinding. Cutting discs are made for cutting metal or steel. Grinding abrasive discs are designed for deburring, cleaning, grinding and even polishing of a variety of materials. Each of these types of application has its set of instructions for the best performance. For example, for primary grinding do not work with a side surface of the disc, you need to move the instrument in lateral direction with an angle from 10 to 30 degrees. Do not ever use cutting abrasive wheels for grinding procedures. This may result into a real injury. For final grinding the working angle must be around 15 degrees.

Disc thickness
Another very important advice is to choose the most appropriate thickness for cutting wheel. The thinner wheel you have, the easier cutting goes. The thicker disc you use, the harder it will be, because thicker discs have larger material resistance. With a thin wheel you will have a more accurate cutting line. They do not heat they do not heat the material so much, but definitely fade away much faster. Thin discs are good for low power angle grinders. By saying thin cutting disc, I mean thickness of 1-1,2 mm for 125 mm diameter. Also keep in mind that thin wheels are more dangerous than thick ones. But I personally did not have any problem with that because anyways there is a fiberglass net which preserves from collapse. And even if a thin disc cracks, the particles will be small and of low weight.

Here you my find info about abrasive disc production process. 

You can write in comments if this article was useful for you. I`ll appreciate your opinion.

Friday, 23 October 2015

Safety Tips for Working with Angle Grinders

safety rules for working with angle grinder

In this article I`d like to tell you some important tips how to make your work with angle grinders safe and to avoid injury. If you follow these safety instructions while working with cutting discs, you will be safe and your work will me smooth and pleasant. All tips are based on my experience.

First, you should know that angle grinders are considered as the most dangerous power tools. The reasons are as follows:
1) A large open space of rotating element (cutting disc)
2) There is no solid support point.
3) High rotation speed

Safety work requires skills gained with experience. If you are a newbie, start with low power tools (those for discs of 115 and 125 mm). Using a small angle grinder you will control load allocation better.  Bigger ones require more experience and knowledge.

Problems with abrasive discs
90% of all injuries while working with an angle grinder are resulted from bad quality discs.
Always check if the discs have cleavage. At the point of touching the material cleavage makes abrupt movement. In this case sometimes the disc may break down spreading its parts with the speed of 300 km per hour or in a better case the toll will be just pulled out of your hands.
Sometimes it is very difficult to see the crack. It may result from stepping on the disc. If you so that someone is stepping on the disc on the ground, immediately inform the operator or do not use that disc. These safety precautions for working with abrasive wheels may save someone`s life.

Use appropriate discs
Here you can read about difference between abrasive discs and diamond discs in detail.
Here I just can add that always you an appropriate disc for your application. Read carefully instruction on discs. For example , never used wood saw blades for hand angle grinder. Teeth over the edge will easily mesh into wood which may bring a very abrupt sudden movement.
Some people try to save money and use TCT saw on angle grinder of 22.2 bore diameter. This is extremely bad and may result into a real danger.
Here is another example. Never use abrasive grinding disc on the wooden surface. First you may fell like the result is good, the disc does not wear out a lot. But working with wood emerges high temperature, and resins may make harmful smell. It can be harmful both for eyes and smelling.

Control before and after operation
Always make sure you have controlled everything before application. Make sure the wheel is fit correctly, the nut is tightly screwed. When you finished cutting, always turn the tool off. Never leave a running machine with a cutting disc on the surface.

I hope those short pieces of advice were useful for you. Here is another article about safety instructions while working with angle grinders.