Buffing Hints

Article From: Products Finishing,

Posted on: 11/1/1997

Hints for super shine, savings and safety...

No matter what line of work you are in, you can always use a few pointers, tips or hints to help you do your job better. Useful hints on polishing and buffing can help you produce super shine, increase savings and improve safety in your work area. The following buffing hints are taken from a booklet produced by Schaffner Manufacturing Company.

Buffing methods. To achieve the ultimate shine on any product, you must use basic buffing motions:

Cut Buffing is where the workpiece travels against the motion of the buffing wheel. Medium to hard pressure is used. This motion produces a smooth surface, semi-bright and uniform, but with residue left on the material.

Color Buffing is where the workpiece travels with the motion of the buffing wheel. Medium to light pressure is used. Color motion produces a bright, shiny, clean surface.

Buffing compound is the tool that actually does the buffing. The buffing wheel is the means of applying and using the compound. Buffing compound should be applied to the buff ahead of the part. If it is applied after the part, it is thrown away from the part and into the exhaust duct, wasting compound.

For economy of labor and material, the buffer should first determine how much color is needed on a part. The buffer should also determine how much less time is needed by preceding the color buff operation with one or more cut or cut/color operations.

Both the workpiece and the bar/buffing compound should be chucked or gripped close to the end in contact with the buff. Gripping the workpiece at the end farthest from the buff results in vibration. Applying the bar compound with six to eight inches exposed can result in the bar breaking. Exposing only two to three inches of the bar to the buff results in even coverage and long life of the bar.

Buff direction. For safety and material savings, the buffs should be placed on the arbor so that the air turbulence and workpiece pressure hold the buff tails closed. A finger buff should turn away from the tails for longer life. Running a buff backwards results in torn, short-lived buffs.

An air-flow bias-type buff should run with the tails held against the buff by the air turbulence, or they will flare out. Backward rotation of the buff may cause air turbulence to open the tails, and the workpiece may be grabbed and torn from the fixture or the cloth from the buff.

Buffing pressure. Buff speed and pressure are two elements that must work together to produce the best finish, safety and economy. The proper pressure must be applied to the workpiece to produce the friction that allows the compound to buff. Inadequate pressure gives no buffing action. Excess pressure will cause the buff speed to be reduced and/or the buff to collapse.

The results of too much pressure include V-belt slippage, if the nut is not tight; Buff slips on the arbor shaft; and the buff will collapse.

Why are the buff and center diameters important? Buffing is most efficiently accomplished within specific speed ranges. Operating above these recommended speeds can cause burning of the buff and lack of compound retention. Operating below these recommended speeds will not produce sufficient polishing action.

The buffing speed is how fast the outer edge of the buff rubs across the part. This is determined by the diameter of the buff and the spindle speed of the machine. Normally, this spindle speed remains the same, but the buff diameter becomes smaller and smaller as the buff wears out, resulting in slower buffing speeds.

The largest diameter possible should be used that produces the upper end of the buff speed range and still permits coverage of the part contour. The smallest center should be used that provides the lower end of the recommended speed range.

An example is the following: If a 16-by-seven-inch buff (16-inch buff and seven-inch center) produces the top and bottom of the speed ratio at a particular rpm, then: 1) A 20-by-seven-inch buff will have a buff diameter that is too big, thus too fast for the job; 2) A 14-by-seven-inch buff will have a buff diameter that is too small and will have to be replaced more often; 3) A 16-by-nine-inch buff would be a waste, since the center is too big and the buff would have to be replaced often; and 4) A 16-by-five-inch buff would have a center too small, thus too slow for the job.

Why should you use a biased-type buff? When you buff with a cloth that has been cut on the bias (a 45-deg angle to the weave) the edges of the cloth cannot unravel, giving longer buff life. A biased-edge also provides more thread ends for the edge or face of the buff to hold compound.

A full-disc buff will fray easily because of the arc of the buff. In a bias-type buff every thread extends from the outer edge of the buff to the metal center and back out the opposite side. This makes it impossible to pull loose.

The cloth of a metal-center, biased-type buff is held in place by a steel-toothed clinch ring. For safe operation, flange pressure must be maintained at the outer edge of the metal ring.

For greatest efficiency and safety, the flanges holding the buffs should press against the outer edge of the teeth on the clinch ring. Pressure from the flanges on the ends of the teeth will ensure a safer, more even wearing buff.

Common mistakes include: 1) Flanges not used and subsequently pressure from the nuts are on the weakest part of the wheel; 2) Flanges too large and pressure is on the cloth material; 3) Flanges too small, which is as bad as no flanges at all; and 4) For a contoured buff, the center sections much be the same diameter to maintain pressure between the flanges.

Grease sticks. Proper use of a grease stick on abrasive belts and Flapwheels® is very important. Using a grease stick on an abrasive belt makes a new belt cut soft and uniform. The grease stick partially fills in between particles to reduce the initial cutting edge.

Using a grease stick prolongs the life of a partially worn belt by enabling it to continue to cut, because the hot metal particles cannot be welded to the belt. Metal bits welded between particles reduce the cutting surface.

Using a grease stick on a Flapwheel extends the life of the Flapwheel and softens the cut to make the buffing operations that follow easier.

Abrasive belts and Flapwheels. There are two types of joints used in making coated abrasive belts, the butt-type and the more common lap-type. The butt-type can be run in either direction. However, it is important both for safety and belt life that the lap-type be run in a direction so that the open end of the lap is trailing. If the lap-type is run backward, the exposed end of the lap may catch on the workpiece and ruin the belt.

A Flapwheel has certain advantages over an abrasive belt. A Flapwheel provides a long-lasting cutting surface. Because there is so much more abrasive, the Flapwheel will last much longer than the belt, prolonging production time. A Flapwheel provides a uniform cutting surface, since it is worn down constantly, exposing new abrasive. This provides 25 to 50 times more working abrasive as a belt. Also, with a belt, if two pieces of the same product, such as chair legs, are done at different time during the belt's life, different finished surfaces may result.

A Flapwheel can conform or adapt to the contour of the workpiece. It would take four persons to do four different operations on one workpiece where one person could do all the abrading jobs at one time with a contoured Flapwheel.

A fast way to shape the face of a Flapwheel is to put a coarse grit, coated abrasive against the wheel while running it backward. A faster way, if your production requirements are large enough, is to have Flapwheels made in the shape of your particular workpiece.

Spray buffing compounds for aluminum, brass, copper, zinc and other non-ferrous metals are the emulsified form of solid buffing compounds. They are water-soluble emulsions that are applied by one of two methods.

Method one is a conventional system. Liquid buffing compound is pumped from a drum or hopper through an air spray system. Air accompanies this compound as it is dispersed from the spray gun. This type of material has viscosities ranging from 10,000 to 65,000 cp.

Method two is an airless high-pressure system. This method uses the principle of aspiration. The liquids are viscous and thick and leave the gun under heavy pressure.

There are also liquid spray buffing compounds for steel and stainless steel. Liquid compound is pumped from a drum or hopper through an air spray system. Air accompanies this compound as it is dispersed from the spray guns. This type material also has viscosities ranging from 10,000 to 65,000 cp.


Comments are reviewed by moderators before they appear to ensure they meet Products Finishing’s submission guidelines.
blog comments powered by Disqus



Suppliers | Products | Experts | News | Articles | Calendar | Process Zones

The Voice of the Finishing Industry Since 1936 Copyright © Gardner Business Media, Inc. 2014

Subscribe | Advertise | Contact Us | All Rights Reserved