Fowler/Bowers XT bore gage heads can have the anvils specially machined to be able to accurately measure threads. These special XT heads can be manufactured to measure the pitch diameter, major diameter, or effective diameter which is also known as the functional diameter. The effective diameter thread heads are the most common as they give a better overall average measurement of the thread. It is a little tedious, but thread heads are available in single point so each individual thread can be measured independently if the customer chooses to do so.
Fowler/Bowers XT thread heads are available to measure threads with a range of 8UN -12” and M4-300mm on the metric side. Thread heads are available in both 2-point and 3-point contacts but 3-point are much more common as it helps the head self-centralize in the thread. Special thread heads are available in the following thread forms: ISO, ANSI, UNC, UNJ, UNS, UNF, Metric, ACME, Whitworth, JIS, Buttress, PG, BSF, BSP, BA, and left handed threads.
Similar to all other Fowler/Bowers XT heads, special thread heads must be set to a master thread ring or certified part prior to use. An operator has two different preset options when using special thread heads. The operator can preset the size of the thread ring into the pistol grip or electronic holemike and the display on the readout will show the actual reading of the thread. The operator can also set “zero” on the thread ring and the readout will display the deviation away from the nominal size.
If you are interested in learning more about Fowler/Bowers thread heads or would like a quote, please email [email protected].