- How do I choose the most appropriate spring material for my spring design?
- Is it possible to obtain a small quantity of a product to check my spring design prior to placing a large production order?
- Is it necessary to specify helix direction on spring blueprints?
- What is the correct way to get an accurate coil count in a spring?
- What is spring index?
- What is the advantage to using 17-7 stainless steel?
- Do you stock catalog springs?
- Can you help with my spring design?
A variety of questions must be asked and answered to arrive at the best spring material including:
- The atmosphere in which the product operates
- The frequency of cycles and the amount of deflection
- The cost of the spring or wireform in relation to the overall project
- The expected life of the product
Some springs are used in products that are discarded in a relatively short time frame and have a low cycle frequency during that time. In those cases the design should specify a general purpose spring wire, which can keep costs down while not affecting product performance.
Conversely stainless steel is often specified in products frequently exposed to moisture. Other spring materials include Hastalloy C-276 alloy (for use in highly corrosive atmospheres), music wire (which is a carbon steel and has the best resiliency to being deflected and distorted), chrome silicon, copper, aluminum, phosphorous bronze and the list goes on.
In a word, yes, however it’s imperative we both understand exactly what we are attempting to accomplish. All of our products are custom manufactured and often the cost to set up equipment and ensure the quality to produce prototypes is little or no different than set-up costs to run a production order; for example if the prototypes require zinc plating the cost for sub contracting may be exactly the same for 10 pieces as for 2,000. However, if spring load is the only concern of the design, prototypes can be evaluated without being plated. We have equipment and methods specifically geared for prototypes and short run production and regularly produce orders for as few as one or two pieces.
Generally, compression springs have an optional helix direction but in special applications such as clutches or drapery hardware the helix may be vital. Torsion springs and extension springs with open hooks are also critical applications where helix specification is mandatory for either assembly, function, or both. It’s always best to present a drawing with the correct helix and end configuration shown as well as the correct written terminology to reinforce the drawing. Refer to the drawing (below) which clarifies left hand helix and right hand helix and avoid terminology such as clockwise and counter-clockwise. Please note, double torsion springs always have one side left hand and one side right hand.
Coils are full 360 degree circles; however, springs often are designed to have not (for example) exactly five coils or exactly eight coils but, rather, four and one-half coils or eight and one-quarter coils. Please refer to the sketch (below).
Spring index is the ratio of wire diameter to the mean spring diameter. The ratio is one calculation for determining manufacturing difficulty and feasibility. An index of 5 to 15 is generally a desirable range and up to 20 should not be a problem. An index of 25 or 30 should be reviewed by both the spring designer and manufacturer for red flags. An index of 40 or over should be avoided if possible. For indexes under 4 use extreme caution in design and quotation. An index of 2.5 or less is approaching impossible.
17-7 stainless steel is a precipitation hardening product. Once formed or coiled, the springs are subjected to a high temperature heating process which increases the material tensile strength. Two common heating processes are Condition CH and TH1050 depending on the initial material stage being Condition C or Condition A, respectively. Since many stainless grades are somewhat weaker than steel, 17-7 is desirable at times since it possesses both the strength of steel as well as the corrosion resistance of stainless.
No, but we have Spring Assortment Kits that tool shops and machine rebuilders find useful.
Yes, we can help with your spring design to improve function by adding or decreasing spring strength, suggesting a more appropriate material for the application or answering various other questions you may have. However, you must have a spring drawing, sketch or written description of the spring or sample with which to start. We are not mechanical design engineers whereby you may have an abstract concept of something you want to build or invent and are depending on us to design a spring from scratch to fit your application.