Chipboard Screws, ideal for all types of timber including Treated Pine are a coarse thread screws with a countersunk flat head and ribs under the head that self embed with the timber surface for a flush or countersunk finish. The screw provides maximum grip and minimum stripout into chipboard, MDF, other composite and soft timbers. It is recommended to drill a pilot hole into some hardwoods so if possible, test on an outcut as performance and outcome vary depending on the type of timber and age. They are all variations of the original galvanise. All self drilling and timber T17 screws from Bolt and Nut Australia are guaranteed to comply to a minimum of Class 3 and extend to Class 4 and the ultimate of protection B8. To determine the TPI of a screw, count the number of threads contained within an inch of length on the fastener. If the screw is less than an inch count ½” of an inch and multiply by 2 How to measure the length of a Timber Screw: Fastener length is generally measured from the point where the surface of the material will be when the fastener is installed to the end of the fastener. Thus, fasteners with heads that sit above the surface are measured from under the head to the end of the fastener, while fasteners that sit flush with the surface are measured from the top of the head to the end of the fastener Thread Length: have been included as a guide only. Due to stock being sourced from multiple suppliers variations do exist. All material is advisory only and its use by anyone is entirely voluntary. Reliance on it for any purpose by anyone is at the sole risk of that person, and Bolt and Nut Australia is not responsible for any loss, claim or damages arising therefrom.