Here are some basic rules for maintaining high quality and cutting fastener costs!
- Use Standard Design Fasteners Wherever Possible.
Specify cold-headed fasteners for increased shear strength and lower costs. Cold-heading eliminates waste and offers a selection of head designs not possible with screw machine parts.
- Cut Variety of Standard Types and Sizes.
Larger inventory of fewer fasteners means less stocking and ordering headaches, lower drilling, tapping, punching and tooling costs; avoids high cost of small quantity orders. Better inventory control and less SKUs to manage and purchase.
- Use ANSI Standard Specifications Wherever Possible.
Use these tolerances for economy: Diameters: Frac. + .015, Dec. +.003 Lengths: Frac. +1/64, Dec. +010 Angles: +2 degrees, Drilled Holes: +.005. Avoid sharp corners on blueprint designs - allow for a radius of .005 to .010 otherwise they will increase cost.
- Use Class 2A and 2B Thread Tolerances.
Class 2A external thread to fit Class 2B internal thread is the most frequently used thread tolerance. This gives a general purpose fit, providing sufficient clearance to minimize fastener driving difficulties during installation. Class 2A thread form allows for a minimum plating buildup.
- Determine if a Standard Design Fastener Will Meet the Design Application Objective.
If there already exists a standard screw design that will meet the design application, it is best to use it because it will be more readily available, quicker delivery in general and will cost less.
- Steel Material Selection.
Use low-carbon steel wherever possible. Use heat heated fasteners for more strength in smaller sizes to reduce size, weight and cost.
- Use Multi-Function Fasteners.
Fasteners can do more than just hold two parts together. They can replace an assembly operation, replace extra parts or perform other functions thereby increasing production while cutting costs and reducing rejections. Good examples are Sems® Screws, Keps® Nuts, Thread-cutters or Self-Drillers.
- Don't Use Custom Designed Fasteners
Avoid custom fasteners unless no standard designed fasteners will suffice for the fastening application. Cost savings will be significant with standard fasteners usage!
- Use Plated and/or Phosphate Coated Fasteners Where the Application Warrants
Use plated or coated fasteners rather than solid more expensive materials to solve corrosive or surface reaction problems. Food industry and salt water environments are notable exceptions.
- Use Recommended Materials on Adjacent Parts.
Avoid galvanic action (corrosion) between non-compatible metals and also use surface treated fasteners.
- Order Maximum Quantities
Order the maximum amount you can to be used for certain period of time even though delivered at different times. Allow enough lead time. Review and evaluate all the Vendor Managed Inventory (VMI) programs offered by your suppliers.
- Provide up-to-date Drawings and Specifications.
Include sample parts or manufacturer's part numbers if available.
- Adhere to IFI Industry Tolerances for Additional Cost Savings.
Keep design requirements as uncomplicated as possible. Consolidate lengths, diameters, materials, head styles and drive recesses for the benefits of "Standardization".
- Involve Your Suppliers in the Design and Application Method.
Sometimes, a newer, more efficient or lower costing fastener can be recommended. Ask for suggestions in improving fastener installation in the work cell, i.e. angle or position of installation, tool choices, etc. Use special designed or engineered fasteners when the application calls for them. Don't be determined to eradicate all special fasteners. Sometimes two or three expensive fasteners or parts can be replaced by a one-piece special cold-headed fastener that has a lower in-place cost and is superior in quality.
- The Real Cost of Fasteners.
Purchase price is not a fastener's real cost! The real cost or the full cost is the "In-Place" cost. That is, purchase price plus labor cost to prepare the application, i.e. drilling, tapping, punching and then the installation cost. Plus the down-time cost and added labor to replace it if it breaks or fails on the assembly line plus any replacement costs necessary in the field. The "In-Place" cost of a fastener can be 5 to 20 times the cost of a fastener. Order fasteners capable of performing the fastening application required - not necessarily the cheapest fastener.
Standardization is the key to saving money! Use standard, commonly used fastener types, styles and sizes. Use as few varieties and sizes as possible; thus cutting costs and saving money. Do not over-specify, for example, tensile strength, corrosion, plating, weight, vibration resistance or one of numerous other reasons. However, be aware there are times a "special" fastener will reduce costs, improve the fastening application and increase production. Never substitute a fastener without checking with engineering first!