Diamond Wheels And Cbn Wheels

Resin Bond Diamond Wheels

JPT Produces Resin Bond Diamond Wheels that is used for maximum performance which reduces production time and increases profits. These wheels help in cutting and grinding various material efficiently and at the lowest possible cost. Bond matrixes are available for dry, mist & flood applications and their advanced bonding technology provides faster cutting and grinding.

Metal Bond Diamond Wheels

Metal Bond Diamond Wheels manufactured by JPT is used in numerous industries across the globe. For the maximum productivity and consistency, sophisticated metallurgical techniques and premium diamonds are used in the manufacturing of Metal Bond Diamond Wheels. Designed with varying degrees of hardness and abrasion resistance, these wheels offer maximum performance and long functional life.

Application of Resin Bonded Wheels

Precision Grinding

• Cylindrical, centerless, surface and internal grinding of carbide tools, cutters, dies, gages, etc. Grinding chip breaker grooves
• Grinding threads in carbide taps and gages
• Sharpening carbide reamers, drills, inserted tooth milling cutters, etc.

Cut - Off and Slotting
• Cutting sintered carbide to size where fast cutting is important

Off Hand Grinding
• Sharpening single point tools where fast cutting action is required
• Grinding new carbide single point tools on a production basis

WHEEL SPEEDS
The ANSI Standard Safety Code B.71-1970-Maximum Operating Speed For Resin Bond Diamond Wheels is 9500 SFPM

Dry Grinding – Minimum-2500 SFPM Maximum - 3000 SFPM
Flood Grinding – Minimum-5000 SFPM Maximum – 6000SFPM

FEEDS AND SPEEDS
Avoid Excessive feeds - for most satisfactory finish and longer wheel life, the following feeds are recommended :
.001" thru 120 grit
.0005" thru 220 grit
.00025 for 240 grit and finer

TABLE SPEEDS : 10 to 40 feet per minute
CROSS FEED : .030 to .100 depending upon the width of the wheel and size of the load.

Suggestions for Extending Diamond Wheel Life

There is no general rule of thumb concerning how long a diamond wheel should last. That depends on you, your equipment and your customers. But, by following a few simple rules, you can make sure that you’re getting the most from your diamond wheels:

1	Avoid Excessive Heat	Excessive heat damages the bond and can cause the premature loss of diamond particles
2.	Grind Wet	Use a full flood coolant directed where the wheel contacts the carbide tip. It might be more convenient to grind dry,but studies have shown that wheel life can be increased by more than 100 percent by grinding with a flood coolant.
3.	Avoid Excessive Feed Rates	Light downfeeds and fast traverse rates result in the lowest total costs.
4.	Area of Contact	Be careful when going from one saw sharpening operation to another, for example, from top to faces with the same specifications. The larger area of contact can be a cause of heat generation when an improper specification is used.
5.	Avoid Vibration	Vibration anywhere in the operation causes pounding, which reduces the life of the diamond wheel and producesa poor surface finish on the tip.
6.	Clamp Correctly	The saw plate should be supported firmly by clamps that are operating correctly and set close to the tip.
7.	Mount Wheel Properly	Clean all dirt from the wheel mount. Check the mount for any nicks or damage that will cause run out, and useflanges that are at least 1/3 of the wheel diameter.
8.	Solid Machine	In order to reduce vibration, place your grinder on the most solid floor possible and bolt down.
9.	Avoid Steel & Braze Contact	Keep the amount of steel ground by your diamond wheel to an absolute minimum. Steel causes diamond pullout,which results in higher wheel wear. Brazing materials load the wheel surface, causing excessive heat generation.
10.	Operate at Safe Speeds	Resinoid wheels used with flood coolant grind most efficiently at a minimum of 5000 SFPM (surface feet perminute) to maximum of 6000 SFPM. Used dry, the minimum / maximum SFPM rates are 2500 to 3000.

CARE OF DIAMOND / CBN WHEELS

Resin Bonds Are Recommended

Although metal and vitreous (glass-like) bonds are sometimes used in diamond wheels designed for grinding cemented carbides, resin (usually phenolic) bonds are preferred.

Resin bonds are resilient, cushioning the diamond abrasive against shock that might cause gross fracture. And, since resin bonds are formulated to wear at the same rate as the friable diamond abrasive, new crystals buried in the bond are exposed when needed. As a consequence, resin-bonded diamond wheels generally remove material up to ten times faster than metal-bonded wheels and twice as fast as vitreous-bonded wheels.

The rate of wheel wear is correspondingly higher. But the reduction in labor and overhead cost per cubic inch of carbide ground more than pays for the increase in diamond wheel cost.

“Hardness” (wear resistance) of resin bonds is an important factor in diamond wheel performance. If a resin bond is too hard, the wheel will not be freecutting. If a bond is too soft, wheel wear will be excessive.

Grinding efficiency can be improved by matching the hardness of the wheel to the specific grinding job. Factors which determine the wheel grade (hardness) are contact area between the wheel and the work, wheel surface speed, wet or dry grinding, grade of carbide, etc.

Basically, a grinding wheel is a toolholder. The tools are crystals (grains) of abrasive embedded in a bond or matrix, which is supported by a core that fits the machine spindle. In a diamond wheel, the abrasive is confined to the wheel rim.

When grinding cemented carbides, the physical properties of the diamond and the bond that holds the abrasive crystals in the wheel rim are of fundamental importance. Using the wrong diamond abrasive or the wrong bond can increase grinding costs substantially.

Diamond content of a wheel is usually expressed in terms of concentration. A 100 - concentration wheel contains 72 carats of diamond abrasive per cubic inch of bond (4.4 carats / cm3) A 50-concentration wheel contains 36 carats per cubic inch (2.2 carats/cm3).

Increasing the diamond concentration of a wheel makes it act “harder” it wears more slowly. With more diamond crystals to share the work, less stress is placed on each crystal.

The degree to which increasing the diamond concentration of a wheel improves wheel life depends on the mesh size of the diamond abrasive. Fine mesh-size abrasive crystals have very small surface areas, which makes it difficult for the resin bond to hold them securely. Premature pullout of abrasive crystals makes the wheel act softer and shortens its life.

Another way diamond wheel life can be improved in both wet and dry grinding is to increase the width of the wheel being used. This increases the wheelworkpiece contact area and for a given material-removal rate reduces the rate of wear of each diamond crystal, hence the rate of wheel wear.

Similar benefits are obtained by increasing the diameter of the diamond wheel. Large-diameter diamond wheels outlast small-diameter wheels by wide margins when run under the same conditions, on the same grade of cemented carbide.

Besides reducing wheel cost per piece, improved wheel life reduces labor and overhead cost per piece. Wheels need to be changed less frequently so the productivity of grinding machines and operators is increased.

Friable Abrasives Cut Fast

Diamond abrasives have many sharp cutting points that remove cemented
carbides cleanly and efficiently during grinding.

As grinding progresses, these cutting points become dull. The dull abrasive tends
to rub, rather than cut, the workpiece surface. Material-removal efficiency is
reduced and much grinding energy is dissipated in the form of heat.

For this reason, friable forms of synthetic diamond abrasive are recommended for wheels designed to grind cemented carbides. A friable diamond crystal undergoes controlled microfracturing under the stresses set up by dull cutting points, creating fresh, sharp points. With these self-sharpening diamond abrasives in the right bond diamond wheels can grind cemented carbides efficiently, with good wheel life.

Trueing Diamond Wheels

Careful wheel mounting is essential when grinding cemented carbides with diamond wheels. For best performance, the wheel should be mounted perfectly normal and concentric to the machine spindle.

Out-of-roundness is not a major problem with cup and face wheels such as Types 11V9, 12, 15 and 6. Straight diamond wheels such as Type 1A1 usually require trueing after mounting.

An out-of-round straight wheel will pound the workpiece surface, reducing wheel life and impairing surface finish. This can be avoided by trueing the wheel so its
entire surface is concentric with the spindle within 0.0005 inch (.0127mm).

Resin-bonded diamond wheels can be quickly trued, using a silicon carbide brake controlled trueing device. However, every effort should be made to mount the wheel to within the required concentricity limits before using the trueing device. This will reduce the loss of valuable diamond wheel rim in the trueing process.

Dressing Improves Wheel Performance

In trueing, the surface of the wheel is uniformly abraded to bring it into truth with the center of rotation. This operation also blunts the diamond abrasive, which is level with the bond after trueing. In this condition, the wheel cannot grind.

To restore the wheel to full cutting efficiency, resin is abraded away with a dressing stick containing fine aluminum oxide abrasive. This exposes the cutting points of the diamond abrasive. When the wheel has between dressed sufficiently, it abrades the dressing stick very rapidly indicating that the wheel is in good condition for grinding.

Maintaining the Wheel

If a diamond wheel frequently tends to lose its free - cutting effectiveness in service, operating conditions probably aren’t just right for that particular job. The wheel can be reconditioned by dressing. But the way the wheel is being used should be critically reexamined.

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