Black Oxide Finish

We have received several inquiries recently regarding black oxide finish.  Black oxide is a conversion coating (as opposed to an applied coating) because it results from a chemical reaction with the iron present in the metal fastener and forms an integral protective surface.  It is a color of the base metal, which neither removes nor deposits metal.  Therefore, it adds, at the most, 5 to 10 millionths of an inch to the fastener's dimensions.  Likewise, it cannot chip, peel or rub off, and the item maintains 99% of its conductivity making black oxide a popular finish for electrical parts.

When a black oxide finish is specified, it is called out as "Black Oxide and Oil".  Other supplementary coatings such as wax or lacquer may be ordered, but fasteners with those finishes are usually not available from stock and must be a special order.  Typically, the oil after-finish is dry to the touch, which gives the part a lustrous appearance and improved lubricity without excessive residue.  The color is a deep black rather than the grayish-black appearance of black phosphate, and remains consistent at temperatures as high as 900 degrees Fahrenheit.  Black oxide also resists abrasions better than phosphate, and one of the most important advantages is that there is almost no risk of hydrogen embrittlement because the process does not involve electro-plating nor does it require an acid-activation.  Case hardened parts need not be baked after receiving a black oxide finish.

Black oxide neither enhances nor detracts from a fastener's resistance to corrosion.  The post-treatment oil application offers good indoor corrosion protection, but a zinc-plated part is more resistant to rust.  However, parts with a black oxide finish will not suffer from white corrosion which can occur over time with electro-plated parts.  To avoid the risk of white corrosive particles (which can cause electrical shorts) many in the electronics industry opt for black oxide instead of zinc plated fasteners.

The popularity of black oxide stainless fasteners is also growing.  In addition to being used for decorative purposes, the finish reduces light glare and reflection and makes the surface of the fastener smoother.  The automotive aftermarket utilizes them in tail-light assemblies, grills and windshield wiper assemblies, to name a few.

Comparing Fine Thread with Coarse Thread Fasteners

Fastener threads provide both load holding when tightened and the ability to move during tightening and loosening.  A fastener's pitch and lead, determined by whether it is coarse or fine thread, is a factor in fastener performance.  A coarse thread will move a larger distance with each rotation than a fine thread of the same diameter.  If speed of assembly is a factor, a coarse thread may be preferred as it will assemble faster.  If adjustment is required, a fine thread will provide a less sensitive adjustment and a greater ability to control adjustment.

Each flank of thread carries a percentage of the clamping load.  This load is not distributed equally among the thread pitches in most applications.  It is generally thought that a fine pitch thread will have a more uniform load distribution among its engaged pitches when installed.

Fine threads can be more susceptible to cross-threading if assembly conditions are not controlled.  In general, both coarse and fine threads have advantages depending on the fastening output required.

Super Cruise XIV, February 5, 2017

Hillco’s annual Super Cruise took place Sunday, February 5, and we had a great turnout! Although it threatened to rain throughout the day, we were lucky to enjoy cool weather and gray skies (perfect for car-show photography!).  The many who did attend had a great time checking out what has become the most diverse collection of cars, trucks, and bikes in one show, enjoying the food and participating in our raffle.

Conversations with the builders helps one appreciate the history, hard work and craftsmanship required in each project.  Many are so beautifully planned and executed that they are more a work of art than merely just a car. From the daily driver to the trailer queen, it was all here on show day, which is the main reason many love attending this event.

On behalf of Hillco’s entire staff, thank you for attending, and a special thank you to Gary Brown (The OC Car Guy) for emceeing and organizing our event and donating to our raffle, Tom Leroux of Hoist Services, Joe and Arlene Jill of Superior Automotive, Stephanie Hill of Stephanie Hill Photography, Los Alamitos Brew Kitchen, Brighton Best International, and Joe Leroux and the Road Devils for their generous donations to our raffle that helped to make Super Cruise XIV a great success.  Special thanks to the Hillco staff for their enthusiasm and support in putting on this event.

Thank you again to all who attended.  We will be posting photos from the event on our Facebook page, so please share with your family and friends.  As most of you already know, Hillco is a family-owned and operated business established in 1976.  Super Cruise Sunday is our annual customer appreciation event which gives us an opportunity to see your projects and raise funds for veterans and first-responders via donation to Gary Sinise Foundation.  We look forward to seeing all of you next year!

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