ACME and Trapezoidal threads are quite common in use. With increasing industrialization and the rapid development in the machineries, their usage is immense. The evolution and the similarities of these gages are interesting to have a look at. Here's what we have to know about them both. ACME thread gages were a new addition to the field only in the 19th century. It came into existence as a result of a previously used, less compatible square thread. These square threads used to be the top preference during the Industrial Revolution, but later became redundant as they were difficult to manufacture and it had weak base. So, the need for a new gage that would help people get over these shortcomings was needed. The square gage had a sharp 90-degree angle on the flank. Hence, ACME thread gages came into existence.
ACME Thread Gages:
ACME thread gages had the modification of the included-angle to 29-degrees which helped in widening the base and made it firm and strong. ACME diameters and the pitches later get established over a period of time. These days, ACME threads are used in precision instruments Hence, you need precision tools to evaluate and determine its tolerance levels. The best tools for the purpose are ACME thread gauges. This is in the US.
Trapezoidal Thread Gages:
In Europe, similar standards and history led to the making of a 20 degree flank angle precision tool which came to be known as the trapezoidal thread gage. The diameter and the pitch measurements are given in metric units. This became the standard precision tool in European countries. These threads are also used in lead screws and other pivotal instruments. These threads have to be strong as well. You need a special gauge to measure the pitch of these trapezoidal threaded screws. They are the trapezoidal thread gauge.
Similarities and The Differences:
There are three main classes of ACME Thread Gauges- the General Purpose one, the Centralizing one and the Stub ACME. 0.50 thread pitch and a 29 degree flank angle are common traits to the General Purpose and Centralizing thread forms. It is important to note that the centralising threads are made to deal with tight tolerance and lesser clearance on the diameter. This is not the case with the general purpose tool. ACME threads follow the same basic design. The difference is that the depth is a little lesser.
There is no much difference in them physically but how they are used makes the difference. ACME has become the standard tool around the globe especially in the US. The European industries have settled with the trapezoidal measures. Although they are the same, they are important in their own ways.
These are some basic information on the ACME and the Trapezoidal standards of thread gages that are popularly used across the globe.