Frequently Asked Questions
Bolt length is measured from where the bolt will meet the surface when installed (under the head for a Hex Head, at the top of the head for a countersunk/flush head bolt) to the tip of the threads.
Bolt diameter refers to the thickness of a bolt at the Grip and/or the Major Thread point.
Nut diameter and washer diameter both should match the diameter of its associated bolt.
There are two terms that describe the smooth area between the head and threads on a bolt, "SHANK" and "GRIP". Both terms are correct to describe the smooth area on a bolt. All shear loads should be positioned on the Shank/Grip area of a bolt. Shank/Grip length is measured from the start of smooth area under the head and ends where the threads start. See the diagram under "How Do You Measure Fasteners" above for an illustration.
Thread pitch is the distance from the top of one thread to the top of the next thread. Example would be a M6-1.00 pitch thread. The distance would be 1mm from the top of one thread to the top of the next thread. A higher thread pitch value indicates "coarse thread" vs lower thread pitch values indicate "fine thread".
Structural grade titanium is equal to most steels. Titanium is not stronger than high strength alloy steels. Mettec has experience producing titanium with strengths ranging from minimum Ultimate Tensile Strength (UTS) 120-195Ksi (827Mpa-1345Mpa). Please refer to Mettec Tech Section for an expanded explanation of strengths of titanium verse steel alloys.
Titanium is 47% lighter than steel and has better corrosion resistance than stainless steel in a salt water environment. This makes titanium ideal for applications where weight and durability are critical for high performance.
Machined threads are single point cut which tears the grains of the material to make thread. A rolled thread is formed by compressing the material with a rolling die. A rolled thread has higher strength and fatigue resistance. A rolled thread is much safer, and this is why aircraft manufactures will specify rolled threads on all fasteners.
Machined fasteners are made with round bar material. When you machine the bar all the grain flow in a machined fastener will be in one direction and will have low fatigue resistance and strength. When fastener heads are forged, the grain flow will resemble the form of a mushroom shape in the transition between the shank and head. The grains become smaller and finer which adds to the strength and fatigue resistance of the fastener. All fasteners in aircraft/spacecraft manufacturing are formed by forging.
Mettec started manufacturing titanium fasteners in 1995. Our services have grown to encompass many different disciplines in manufacturing including Hot Forging, Centerless Grinding, Thread Rolling, CNC lathes, CNC mills, Deep Hole Drilling, Shot Peening, and PVD coatings. Take a look to find out more about Mettec's custom manufacturing manufacturing capabilities.
All OEMs make their fasteners from steel. Steel will rust or corrode if not properly coated. Due to price and environmental reasons most manufacturers have gone to cheaper coatings. When a fastener is tightened with a wrench, the wrench will scratch and deform the surface on the head which will lead to corrosion. Mettec makes titanium fasteners that will not corrode and will look shiny for many years. One other advantage is that Mettec titanium fasteners are 47% lighter than steel. By using titanium fasteners you will gain performance with no corrosion problems and reduce the weight of your machine.