STAINLESS STEEL POLISHING & BUFFING
When stainless parts are delivered to the polishing or buffing department, they lack the inherent beauty and luster that spell real sales appeal. The work accomplished at this point puts the Cinderalla fable to shame. From a homely looking article, the “magic” of polishing and buffing puts a dress on stainless steel that is permanently beautiful and functional. For here beauty is more than skin deep, offering a lifetime of service, because it stays that way for years.
Functionally, polishing gives stainless maximum corrosion resistance, often at considerably less cost than good chrome plating jobs.
The cost of bright-finishing
stainless steel depends entirely upon the condition of the surfaces when the
parts are delivered to the polishing or buffing room. Careless handling in
fabrication causing deep scratches or tool marks adds needlessly to the cost of
finishing.
Polishing: Strictly speaking, polishing is a cutting operation used to prepare a surface for final buffing. The amount of polishing required depends upon the original surface of the parts. Very little actual polishing is done on stampings and rolled moldings made from the lighter gauges of stainless strip. The finish on this strip is so good that a light buff is frequently all that is necessary. On heavy-gauge strip, polishing begins to enter the picture.
Forgings, machined parts or parts formed from strip and that have been badly scratched in fabrication or handling require a series of polishing steps preparatory to buffing. When machined parts require polishing, the time and expense for doing this work can be reduced about 50% by using a free-machining grade.
If coarse abrasives are first used, then finer abrasives must be used successively until the surface is finally smooth enough to permit buffing. The complete series of abrasives will run NO. 80, No. 120, No. 150, No. 180, No. 200. Start with the finest abrasive that will efficiently cut down the surface.
Turkish emery is much better than artificial emery because it doesn’t scratch as deep, and the next finer wheel will do a better job. On very rough work, start with the artificial emery, but after the No. 150 artificial, go to No. 150 Turkish )at cross angles to the old scratches when possible), then continue with Turkish emery.
Use setup wheels or continuous polishing belts operating at about
5,000/6,000 surface feet per minute. Note that these speeds are considerably
slower than buffing speeds.
Oiling Out: This is an intermediate step between polishing and buffing. Oiling out will start after the No. 300 wheel.
For oiling out, use a fairly, stiff sewed rag wheel and surface it with Turkish flour emery. This is done in the same manner as any other “setup” wheel. When the wheel is dry, first break it down with emery stone to take off the sharp edges, then saturate with tallow or grease. Keep enough grease on the wheel at all times to prevent burning. The use of this grease gives rise to the name of the process.
Oiling out is done at 5,000/6,000 surface feet per minute, the same as
polishing.
Buffing: A cutting buff
followed by a color buff is usually employed. If stampings made from the lighter
gauges of stainless cold rolled strip have not been badly scratched, the
finishing job can frequently start right here.
Buffing lathes for stainless steel should not run under 10,000 surface feet per minute, and 12,000 to 15,000 feet is preferable. This may mean spindle speeds ahs high as 3,000 rpm. For color buffing, speeds in the range of 7,000/9,000 surface feet per minute may produce better results.
Do not use red rouge or rose Tripoli on stainless steel, use the special
buffing compound prepared expressly for this purpose. Buffing compounds
containing iron oxide will cause rust pitting on the stainless surfaces.
When trouble is encountered in buffing, it is usually due to:
(a)
Too soft a wheel, or one which scratches (from the knots in stitching).
(b)
Too slow speed on the wheel.
(c)
Trying to cut and color in one operation.
(d)
Using the wrong kind of compound.
(e)
Trying to buff a surface that is not good enough to start with.
f)
All the foregoing combined to make the operator “lay on too heavy”
and overheat the work. This gives a brown cast, or a dull luster that is not
typical of properly finished stainless steel.
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