The diamonds used in the manufacture of SMI diamond grinding wheels can be classified into two categories:
natural diamond and synthetic diamonds. Every since synthetic diamonds were first introduced in 1957. Their applications have been steadily increasing.Now they are acceptedas the principal material for diamond grinding wheels.
Two important achievements in the history of synthetic diamonds are the development of strong.though diamond grits used for saw blades and the improvement of the grits for resinoid bonds. some grits for resinoid bonds are coated with metal which enables the resinoid bond grinding wheels to achieve better performance.
Diamond powder is commercially available in 50 grades and each grade has its own unique features. Diamonds may be classifiedin to the following
two catagories in term of bonding method:
• RESINOID BOND
• METAL BOND OR VITRIFIED BOND
The grit typed and gritsizes of grinding wheels can be selected depending on workpieces, bonds, and grinding conditions.To help us design the grinding wheels best suited to your purpose.
concentration is the content of diamonds in a unit volume of a grinding wheel.
when content is 25 volume % concantration is 100,which is equivalent to 4.4cts/cc of diamond in the grinding wheel.the relationship among grits content(in volume %),concantration and diamond content(in cts /cc)is as follows:
|Grit content (volume%)||Concentration||Diamond Content (cts/cc)|
AS illustrated above, the price of grinding wheel largely depends on its concentration.
since the appropriate concantration of a wheel depends on work materials, grinding conditions, etc.
Diamond grit size are classified into 22 grades as shown in the following table. The nominal grit size of a grinding wheel indicates the coarsets size grits which are present in the wheel.
For instance,the grits in the #140/170 range pass through a #140 sieve and are trapped by a #170 sieve.The grit size in this range is noted as #140.
Grit size classification by sieves is not only feasible up to # 135 mesh. After this, the grit sizs is still indicated by number (#……)but the method of classification is different.Grit size can br more accurately understood by correlating them to their respective mesh size and grit sizescatter in diameter (see chart below)
|Normal Grit Size (Mesh)||Grit Size Range in Mesh of the Grits Use||FEPA||Normal Grit Size (Mesh)||Grit Size Range in Mesh of the Grits Use||FEPA|
|20||20/30||D 852||230||230/270||D 64|
|30||30/40||D 602||270||270/325||D 54|
|40||40/50||D 426||325||325/400||D 46|
|50||50/60||D 301||400||400/500||D 38|
|60||60/80||D 252||600||500/600||D 30|
|80||80/100||D 181||800||600/800||D 25|
|100||100/120||D 151||1000||800/1000||D 15|
There are three alternative bonding methods :resinoid bond, metal bond and vitrified bond
Resinoid bond grinding wkeels are manufactured by using resinoid bonds to bond diamond grits.
there are two types of resinoid bonds:the phenol resin type and the polymide resin type. The phenol resin type is currently in more common usage.
Resinoid bond grinding wkeels have good elasticity, fine surfacefinish, and high grinding performance.They are effectivefor
(1) grinding of cementebcarbide
(2)combination grinding of cemented and hardened steel
(3)grinding of cermet
(4)precision grinding of magnatic materials glass,ceramics,etc
polymide wheels are recommendeb for heavy grinding and creep -feed grinding.
Metal bond grinding wheel are manufactured by sintering metal powder to bond diamond grits.These grits are superior in grits retention and thereforepreferred
(1)when a long service is required
(2)when wear of the grinding wheel needs to be minimized(such as in form grinding)
(3)in hand grinding of cemented carbide
(4)in profile grinding
(5)in the cutting and grinding of hand ,and brittle materials such as ceramics,glass and quratz
(6)in the cutting and grinding of magnetic materials such as ferrite
(7)in the cutting and grinding of the stone
(8)in the cutting and grinding of graphite,etc
The high grit retention quality of metal bond can also cause grazingor loading.the increaseof grinding pressure and of heatingdue to loading may cause thermaldamage to the workpiece. in order to prevent thermal damage,please choose the grinding process, conditions,coolant, dressing intervals,etccarefully.