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Need brushed and mirror finishes on areas of the same part

We are a metal fabricator who is looking at a potential job that would require both a #4 brush finish on the majority of the part, but with a highly polished "stripe" that runs lengthwise of the part. The material would be either 439 or 201 stainless steel. The application is an appliance handle and the profile is somewhat of a "D" shape. There are small flats (approx. 1/4") in the profile on either side of the straight part of the D shape. The brushing would be linear over the majority of the handle, but these flats or stripes would need to be highly polished. We can do the linear brush or we can do the polish. The problem that we are facing is how to separate the two finishes with a crisp delineation - not letting the brush bleed into the polished and not letting the polish bleed into the brush area. We are looking for suggestions/help/equipment recommendations.

John Hale
Manufacturer - Athens, Tennessee, USA
February 10, 2011

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You need to do the brushed finish first, then by use of an adequate permanent mask fixture, do the polishing. Preferably use hardened steel for the mask to give it a longer life. For very intricate geometries, electroformed nickel or nickel-cobalt masks are good options.
G. Marrufo-Mexico

Guillermo Marrufo
Monterrey, NL, Mexico
First of two simultaneous responses -- February 15, 2011

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I am not sure what a #4 satin finish is. When I polish the slide on a 1911 Colt automatic I would polish the whole part to a bright finish. Then I would mask it with a metallic tape, usually aluminum, on the sides and use a fine greaseless compound (180 grit) on the top of it to reduce glare. You have to be very careful to run parallel to the tape or it would peel it back and brush the areas that you want to keep bright.

Frank DeGuire
- St. Louis, Missouri, USA
Second of two simultaneous responses -- February 16, 2011

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G. Marrufo,
May I know what kind of electroformed nickel or nickel-cobalt masks is that?
I am having difficulty in getting polished nickel finish for aluminium profile.
Seeking for your expertise.
Thanks.

Jay Lee
- Klang, Selangor, Malaysia
February 24, 2011

#4 brush finish is typically what is found on stainless steel appliance doors/handles. We have considered some kind of mask, but that does not lend itself well to high volume production. We have found it is better to start with polished material and add the #4 finish. Trying to polish a #4 finish out to a mirror finish is not feasible.

John Hale
Metal fabricator - Athens, Tennessee, USA
First of two simultaneous responses -- February 25, 2011

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Electroformed masks are free standing forms (shells) made of nickel or nickel alloy that match exactly to your part surface and geometry. Frequently used for selective painting or blasting surfaces, their advantage is that they can follow intricate shapes easily and are hard, tough and rustproof. Toys and auto car wheels are good examples of parts painted and blasted using them.
G. Marrufo-Monterrey, Mexico

Guillermo Marrufo
Monterrey, NL, Mexico
Second of two simultaneous responses -- February 26, 2011