From what we have already discussed, the basic diameters of a pair of external and internal threads precisely match each other. However, most of the time we provide some allowances to our threads to have some leeway when fitting them together. This is where metric thread classes come into play. Here are the equations we use to find the fundamental deviations depending on what tolerance position the threads need to be: T d ( n ) = k × ( 180 × P 2 / 3 − 3.15 × P − 1 / 2 ) / 1000 \small{T_\text{d}(n) = k \times (180 \times P For G position: E I = ( 15 + 11 × P ) / 1000 \small{EI = (15 + 11 \times P) / 1000} E I = ( 15 + 11 × P ) /1000; and

The 250 times table lists multiples of 250, which is the multiplication of any natural number with 250. The table of 250 can also be represented as the repeated addition of 250 . The 250 times table is given below both in multiplication and addition form.On the other hand, here are the different general equations that we use to determine the tolerances based on the tolerance grade of the thread:

For g position: e s = − ( 15 + 11 × P ) / 1000 \small{es = -(15 + 11 \times P) / 1000} es = − ( 15 + 11 × P ) /1000; and The table of 250 chart is given here to assist students in reviewing the multiples of 250 up to 20 whenever needed. The image of the table of 250 presented can be used as a flashcard while memorising the multiplication table of 250. For e position: e s = − ( 50 + 11 × P ) / 1000 \small{es = -(50 + 11 \times P) / 1000} es = − ( 50 + 11 × P ) /1000;T T T – Tolerances for their corresponding diameters (i.e., T d2 T_\text{d2} T d2 ​ is the external thread pitch diameter ( d 2 d_2 d 2 ​ ) tolerance); and Metric thread classes indicate a metric thread's tolerance grade and tolerance position. Each tolerance grade and position have corresponding equations that will tell us how much deeper we should cut or cold-roll the threads to achieve those allowances we want. However, there are limitations as to how much we could deviate from the basic thread dimensions. Therefore, it's good to know our thread's allowable maximum and minimum diameters. For f position: e s = − ( 30 + 11 × P ) / 1000 \small{es = -(30 + 11 \times P) / 1000} es = − ( 30 + 11 × P ) /1000;