Threads are undoubtedly one of the more familiar mechanical devices we use in the modern world to open plastic bottles or assemble furniture. Almost every machine uses them in one way or another.
It’s easy to take them for granted as something ordinary these days. But the thread is really one of the great leaps forward in human engineering, and the invention of creating machines of different shapes and sizes, and with increasing precision.So as a technician, machinist or engineer you absolutely need to have an essential understanding of threads.
How to Identify Thread Pitch and Size
Pitch and size are very important for those who use accessories or use screws.
The types of threads can be divided into several according to their function and shape:
·Straight threads: Used to join two parts or components, characterized by pitch threads that are straight rather than curved, they are used to create a mechanical connection but do not provide sealing capabilities.
·Tapered threads: Used to create a sealed connection, characterized by slopes on the inner and outer surfaces, and the slopes on the outer surface pass through the flexible seal to provide sealing capabilities.
·Ring threads: used to create a reliable connection, characterized by ring-shaped inner and outer surfaces, and fasteners on the outer surface to provide threaded connection capabilities.
·Cap threads: used to create a sealed connection, which is characterized by slopes on the inner and outer surfaces, and the outer surface is fastened by a nut to provide sealing capabilities.
·Internal threads: used to create threaded connections, which are characterized by straight outer surfaces, threads on the inner surface, and fasteners on the outer surface to provide threaded connection capabilities.
Calipers, thread inspectors(thread gauges), thread identification guides are required before determining thread pitch and size.
First way- check if it is a beveled screw or a parallel screw
Beveled Screws: Angled relative to the centerline
Parallel Screws: Parallel to Centerline
Second way -Use calipers
Use calipers to measure the cusp-to-cusp distances of the first, fourth, and last threads of the external or internal thread.
If the diameter increases from the male end and decreases from the female end, it is a tapered thread.
If the diameters are the same, they are parallel threads.
Now use a caliper to measure the diameter from the top to the top of the male or female thread, for tapered screws measure the 4th or 5th screw. For parallel threads, the entire thread needs to be measured.
Next, determine the thread
Use a thread gauge to check the size that matches imperial or metric threads, but be careful because each thread is very similar.
Finally, use the obtained information: thread category, nominal diameter, and the thread pitch to determine your screw size and use the thread identification guide to identify threads.
How to measure thread gauge wear?
Thread gauge wear should be measured by examining the surface condition of the threads. The degree of thread gauge wear can be identified based on phenomena on the thread surface such as scratches, wear or cracks.
1. Preparation: Prepare the gauge, clean the surface of the thread detection area, wipe the surface with a damp cloth, and use an effective lubricant to reduce friction.
2. Calibration: Measure the original size of the thread with a gauge to determine its standard size.
3. Inspection: Check the surface of the thread, if there is wear or damage, use a gauge to measure the size of the wear and damage.
4.Report: According to the test results, prepare a wear report to record the dimensional changes of the thread during the test.