- Overview
- Product Description
- FAQ
- Company Profile
- Our Advantages
- Certifications
Basic Info.
Product Description
302 stainless steel utility extension spring 4 inch overall lg
The ends on the extension springs offered in our stock inventory are the common machine-made hook and full-loop configurations.
#1 ATTN: Read This Before BuyingA. Due to the internet and computer display solutions. The actual products may differ from
the pictures. Please contact our salesmen for further assistance.
B. All the extension springs, compression springs, torsion springs, wire forms can be made in customized demands.
C. We appreciate Drawing-Guide Production, Please send us a spring drawing as possible as you can when you inquiry.
D. We appreciate your inquiries and you are welcome all the time!
For a better understanding of your demand, please learn the basics of extension spring manufacturing.
#2 Working Drawing of an Extension spring
#3 Different Hook End Types of Helical Extension Springs
Various types of ends are used to attach the extension spring to the source of the force. They include hooks or eyes at varying positions or distances from the body of the spring, reduced and expanded eyes on the side or in the center of the spring, extended loops, threaded inserts, and even rectangular or teardrop-shaped ends. By far the most common is the machine loop and crossover loop. These ends are made with standard tools in one operation and should be specified when possible to minimize cost.
Unlike compression springs, extension springs do not have a solid stop to prevent overloading. Because of this design stress levels are lower for extension springs than for compression. A special type of extension spring called a drawbar spring has a solid stop and is a type of compression spring with special hooks.
#4 Available Coating Method
Due to the government's environment policy, all the coating materials are prior to RoHS standards. Please take RoHS standard coating as possible as you can. Below is a table for reference, you can simply learn the cost of each coating method.
| Coating Method | Cost | Does it Meet the RoHS requirement? | Remark |
| Unplated | None | Yes | |
| Anti Rust Oil | Lowest | Yes | |
| Black Oxide/Oxide | Lower | Yes | |
| Normal Zinc coating | normal | No | |
| Trivalent Zinc coating | High | Yes | Normally 8~10μ thickness, 48 hours without white rust |
| Nickel Plated | normal | Yes | |
| Electrophoresis | Higher | Yes | |
| Painting | Very High | Yes | require a longer delivery time |
| Stainless steel Washing | normal | Yes | |
| Stainless Steel Electro-polish | Highest | Yes | This coating cost more than the others |
Q: Which kind of materials are available? Do they meet RoHS certification?
A: DoFo Spring is able to manufacture different spring types of compression springs, extension springs, torsion springs, wire forms with a large range of High-Grade Spring Steel - Carbon steel - Stainless steel - Music Wire, all comply to the RoHS standard. The wire diameter is available from 0.001 inches to 0.075 inches, which can meet the requirement of different applications.
Q: Do you support orders in small quantities or do you only accept large runs?
A: DoFo Spring manufactures large quantity springs, small quantity springs based on your demand. We will work with you to choose the most effective solution.
Q: Does DOFO spring offer DESIGN service OR initial ASSISTANCE ON SPRINGS?
A: Our engineers could give initial assistance on the design and advise to lower the production cost. Our engineer has years of experience in spring design. We could provide drawing format in CAD, 3D, and 2D design layout as well as prototype development.
Q: What is the typical lead time for custom springs?
A: The lead time varies in custom springs. For compression springs, extension springs, torsion springs, wire forms in our mold range, we are able to deliver within 25 days. However, for some complex shapes of springs, the delivery time would be around 30~40 days.
Q: Do you charge custom spring samples?
A: We make the custom springs sample charge as a subscription of formal order. In other words, the sample charge could be refunded when we receive the order. However, if your sample requires an additional mold, we will charge it.
Q: If we order large quantity springs, will you house the springs, wire forms, and ship to us based on a required basis?
A: Our warehouse provides specific stock services for long-term business. You can make your shipment schedule on an annual, monthly basis. We will ship on a specific schedule.
Q: What payment term do we accept for spring orders?
A: We could accept payment terms based on T/T, L/C at sight, DP, Westunion.
If any question, please contact us directly.
