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What size should I Purchase?

No one product or application is alike. With such a variety of sizes to choose from along endless ways in which they can be used, figuring out what hardware to use can become a daunting task. In an effort to lend a helping hand we have put together this guide.

Whether you are in the designing, prototyping or hardware replacement stages of a product we hope you'll find this guide useful. The information presented below pertains to items found on this website and was designed to incorporate the use of standard and readily available tools and is to be used as a reference only.

Important: All our Screw and Post product titles refer to the shank length of that product.

Chicago Posts

  • Post Shank Length:
    • Post length is measured starting from underneath the head to the end of the shank.
    • Due to the design and manufacturing procedures involved, our screw and post combinations when used together do not bottom out when fastened all the way regardless of what length screw is being used. Therefor please allow for some additional length on top of the length being purchased as follows:
      • #4 and #8 Threads: Allow up to an additional 0.020" (0.51mm) when using same length post and screw together. Example: When using a 1/4" (6.3mm) shank length, expect a total spacing or holding capacity between the heads of 0.270" (6.85mm) when fastened all the way.
      • We have found that using a screw shank length one size below the post shank length being used will provide a slightly tighter fit, roughly 0.005" (0.13mm) tighter. Example: If using a 1/4" (6.3mm) shank length post, use a 3/16" (4.7mm) shank length screw.
      • Please note for some applications this added spacing may be insignificant but should be taken into account when working with precise dimensions and materials.
    • The post length should be shorter or equal to the thickness of the material to be bound or fastened. 
    • Going too long will result in swivel like movement and loose fit.
    • When being used to bind dense materials such as metal, plastic or wood, consider a smaller length versus the exact length (when available) as these materials do not compress and you may end up with a loose fit.
    • Post Shank Hole Diameter:
      • Hard Materials (Metal, Plastic, etc...): We recommend the diameter of the hole in which the post will be inserted through be a minimum of .005" (.13mm) larger than the size of the post shank diameter. This will ensure a precise fit and allows for any variance among pieces. Please note that when drilling such a precise hole minor things may adversely affect fitment such as burrs left behind after drilling. For our #8 thread posts we recommend using a #4 drill bit. #4 being the minimum clearance recommended for a precise fit. For our #4 thread posts we recommend using a #20 drill bit. #20 being the minimum clearance recommended for a precise fit. 
      • Soft Materials (Leather): For #8 thread posts use our 13/64" punchFor #4 thread posts use our 5/32" punch.
      • Using too big of a hole will result in a loose fit and reduce the holding power underneath the head possibly compromising the hold. For head diameter size please refer to specific product page.

    Chicago Screws

      • Screw Shank Length
        • Screw shank length is measured starting from underneath the head to the end of the shank.
        • Our recommended minimum thread engagement length for a #8 screw when being used in conjunction with a Chicago Post is 1/8" or 75% of the length of the Chicago Post, whichever is greatest. (Please reference Chicago Post section above on how to measure length of post)
        • Not adhering to the above guidelines:
          • You risk compromising the structural strength of the screw and post combination.
        • Although not required, at your discretion we recommend using thread locker. For convenience we offer the following thread lockers.
          • If your product allows for interchanging of hardware finishes or is repairable we recommend using a low strength thread locker to simply prevent the screw from backing out prematurely yet allow for future removal.
          • If you don't expect to ever have to remove the fasteners then a high strength permanent thread locker will do the job.
          • Screw Shank Hole Diameter (Where applicable):
            • Hard Materials: The diameter of the hole in which the screw shank will be inserted through should be a minimum of .005" (.13mm) larger than the diameter of the screw shank, also known as major diameter when speaking of threads. For a #8 thread we recommend using a #19 drill bit. #19 being the minimum clearance recommended for a precise fit. For a #4 thread we recommend using a #32 drill bit. #32 being the minimum clearance recommended for a precise fit. For a #3 thread we recommend using a #37 drill bit#37 being the minimum clearance recommended for a precise fit.
            • Soft Materials: For Screws with #8 thread use our 3/16" punch. For Screws with #3 or #4 thread use our 1/8" punch.
            • Using too big of a hole will result in a loose fit and reduce the holding power underneath the head.

             Still need help? If so, please contact us and provide us with your question, concern or issue at hand. We'll be glad to help!



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