Grade 1-4 are very precise grades Primarily used for Gage making & similar precision works, although grade 4 can be used for precise production works.
Grade 5-16 represent a progressive series suitable for cutting operation such as turning, boring, grinding, milling & sawing. Grade 5 is the most precise grade obtained by fine grinding & lapping. Grade 16 is the coarsest grade for rough sawing & machining.
Grade 12-16 are intended for manufacturing operation such as pressing, rolling & other forming operations.
Tolerance position letters
Fundamental positions are expressed by "Tolerance position letters". Capital letters are used for internal dimensions (bore) and lower case letters are used for external dimensions (shaft).
There are 28 possible letters.They are A, B, C, CD, D, E, EF, F, FG, G, H, JS, J, K, M, N, P, R, S, T, U, V, X, Y, Z, ZA, ZB, ZC for Internal dimensions.
There are 28 possible letters.They are a, b, c, cd, d, e, ef, f, fg, g, h, js, j, k, m, n, p, r, s, t, u, v, z, y, z, za, zb, zc for External dimensions.
The letters "I, L, O, W, Q" & "i,l, o, w, q" are not used.
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| Tolerance Grade for Internal & External feature |
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| Fits |
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| Application of International Tolerance Grade range Fig:1 |
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| Application of International Tolerance Grade range Fig:2
Below is the ISO Tolerance Chart for reference.
 
Find the questions & answers for the tolerance grades using the above ISO Tolerance Chart.
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| Question No:1 |
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| Answer for Question No:1
Have the below Fit calculation block as reference and solve the question No:2.
Question No:2
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