Precision shoulder screws are machine screws, but include a unique, unthreaded section between the head and threads. This shoulder allows for these screws to be used in a wide range of applications. Most commonly, you will see this shoulder screw acting as the pivot point, locating pin, dowel rod, axle or in other unique ways.
What makes Lyn-Tron precision shoulder screws unique is the high tolerance on the shoulder diameter. Standard shoulder bolts have a range of 0.002”. Lyn-Ton precision shoulder screws are held to a tolerance range of 0.001” for a very precise fit. We offer these in steel, stainless steel and brass.
Step 1 - Screw Type
Lyn-Tron provides shoulder screws with different materials, thread sizes, and head heights to work in a variety of different environments. You can start by reviewing our catalog of Lyn-Tron Precision Shoulder screws or by looking at our offering of Mill Spec Precision Shoulder Screws. Lyn-Tron manufactures both lines to the same high quality standards.
Lyn-Tron Precision Shoulder Screws
Screws with a hex socket drive for use with a hex key in installation. Offered in different materials and thread sizes for many applications.
Screws with a slotted drive for use with a flathead screwdriver. Offered in different materials and thread sizes for many applications.
Mil-Spec Shoulder Screws
Hex Drive Precision Shoulder Screws are made following the Dimensions, materials and passivation methods specified and approved by the National Aerospace Standards Committee in the NASM51576 Standard. This standard is maintained and published by AIA.
Slotted Precision Shoulder Screws made to the Dimensions, Materials and Passivation methods as specified and approved by the National Aerospace Standards Committee. These shoulder screws are made to the NASM51575 Standard, maintained and published by AIA for Slotted Precision Shoulder Screws.
Step 2 - Shoulder Dimension
The shoulder section on these screws is what makes them unique. Lyn-Tron offers these shoulders in a wide range of Diameters and Lengths. You can find these in both inch and metric sizing.
Inch Sizes available
|Standard Diameters (Nominal)||Standard Lengths Offered|
|1/8||1/8 - 1/2”|
|5/32||1/8 - 3/4”|
|3/16||1/8 - 1 1/2”|
|1/4||1/8 - 1 1/2”|
|5/16||1/4 - 1”|
|3/8||1/4 - 1”|
|1/2||1/4 - 1”|
Metric Sizes Available
|Standard Metric Diameters||Standard Lengths Offered|
|3.16mm||3 - 13mm|
|3.96mm||3 - 20mm|
|4.75mm||3 - 25mm|
|6.34mm||3 - 25mm|
|7.93mm||3 - 25mm|
|9.51mm||3 - 25mm|
Step 3 - Material
The material used for the shoulder screw will have a direct effect on the screw’s strength, corrosion resistance and cost.
Is very strong, but its corrosion resistance is limited. Leave these screws exposed to the elements and they will quickly rust. Plating will improve their corrosion resistance and allow them to last longer, but their effectiveness in harsh environments will always be limited. Best used in applications where the screw will be protected either indoors or inside an enclosure.
Is very strong and has excellent corrosion resistance. The addition of chromium to steel gives these screws a naturally forming, corrosion resistant layer. Most Lyn-Tron shoulder screws are made out of 303 stainless steel and are used in many aerospace environments and outdoor applications. For salt water environments, request 316 stainless which is nicknamed the “marine grade”. This grade has higher levels of nickel and molybdenum to be more resistant to salt.
Is easy to machine and is generally more corrosion resistant than stainless steel. Brass also has excellent properties for electrical and thermal conductivity as well as a higher thermal expansion coefficient. These properties allow brass shoulder screws to perform well in many high temperature applications and outdoor or marine environments.
Step 4 - Thread Size
Shoulder screws come in all common thread sizes. Generally, each shoulder diameter is mated with a corresponding thread size, but others do have different thread options. Lyn-Tron can offer non-standard combinations upon request.
Shoulder Diameter and Thread Size Combination of Standard Precision Shoulder Screws
|Shoulder Diameter (Nominal)||Thread Size|
|3/8||1/4-20 or 5/16-18|
|Shoulder Diameter||Thread Size|
Step 5 - Head Height
For a long time, shoulder screws only came with one head height. As our screws have become more popular, situations have developed where the height of the head would be in the way of other components once installed. We now offer all our shoulder screws in 3 different head heights: Regular, Low Profile and Ultra-Low profile.
Low-Profile head height will be roughly two-thirds the head height of regular shoulder screws. Use them in applications where extra clearance is needed such as the inside of machinery. Ultra-Low Profile shoulder screws will be roughly one-third the head height of a regular shoulder screw. Use them in tight-fitting applications where extra space is needed.
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