Can Portland Bolt add more thread to our existing bolts?

Basically, there are 3 different configurations of threads:

  1. Full-body cut thread
  2. Reduced-body rolled threads
  3. Full-body rolled threads

Full Body Cut Thread

Full body cut threads use full size round bar and the threads are cut into the steel. This is a commonly used method, especially on larger diameter product, long length product, and small quantity runs. This thread configuration can have the threads extended. We have to line up the threading dies with the existing threads and then continue cutting threads up to the new desired thread length. One note though, if the parts are hot-dip galvanized, we must strip the parts of the galvanizing, re-thread, then re-galvanize. It may be just as cost effective to remake the parts in this situation.

Reduced Body Rolled Threads

Reduced body rolled threads are made using pitch diameter round bar which is  ½ way between the OD of thread and the root diameter, so the threads can be formed through a rolling process. This type of thread is commonly found on right angle bend anchor bolts and product manufactured to the ASTM F1554 anchor bolt specification. Some companies may be willing to extend rolled threads, but this is not an option for us. It is extremely easy to ruin a set of threading dies when rerolling bolts.  Therefore, this is something we are not willing to do. Cutting additional thread length will not work on pitch diameter material.

Full Body Rolled Threads

Full body rolled threads use full size material that gets extruded down to pitch diameter and then the threads are rolled. This is a commonly used method for cold headed product like A325 structural bolts. The product is small diameter, short length, and high volume. This configuration cannot have additional threads added. Although the unthreaded shank is full size and can be cut threaded, the extrusion angle causes incomplete threads which will not meet threading specifications.

If you need information about a specific situation, please contact us. We will be happy to clarify the options available to you.

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