Enter the size with a fit (40 H7/g6, 40 H7 g6, 40H7/g6) or one class (60 k6, hole 45 H8, shaft 30 h6), or pick the size and the classes from the lists. The diameter sign or dia. in front of the size is read too. A measured bore or shaft goes in the fields below: the finder says whether it is inside the zone and by how much it is outside.
One reading says little about a worn or oval part: measure in several places along it and in two directions.
Shafts, bushes, pins, bearing seats and housing bores on pumps, compressors and deck machinery are made to fits marked on the drawing: H7/g6, H7/k6, H7/p6. Enter the nominal size with the fit or one class (40 H7/g6, shaft 30 h6, 100 H7), or pick them from the lists: the finder gives the upper and lower deviation and the limits of size of the hole and the shaft, the largest and smallest clearance or interference, draws both zones to scale, checks a measured diameter and writes an RFQ line.
It covers nominal sizes over 3 mm up to 250 mm and the classes listed below, to ISO 286-1 and ISO 286-2. Which fit a part needs comes from its drawing or its maker, not from this finder.
A capital letter is a hole class (H7), a small letter a shaft class (g6); written together, H7/g6, they make a fit on one nominal size. The letter places the zone against the nominal size: H holes and h shafts start at it, F and G holes lie above it, K holes either side of it and M, N and P holes below it; e, f and g shafts lie below it, js shafts either side of it and k to s shafts above it.
The number is the standard tolerance grade, IT6, IT7, IT8, IT9 or IT11 here: it sets the tolerance, the width of the zone in micrometres, which grows with the size. At 40 mm IT7 is 25 micrometres, at 100 mm 35 micrometres.
Hole minus shaft at the limits of size gives the largest and the smallest clearance; a negative clearance is an interference. If both are clearances, it is a clearance fit; if both are interferences, an interference fit; if one is a clearance and the other an interference, a transition fit.
| Nominal size, mm | IT6 | IT7 | IT8 | IT9 | IT11 |
|---|---|---|---|---|---|
| 3–6 | 8 | 12 | 18 | 30 | 75 |
| 6–10 | 9 | 15 | 22 | 36 | 90 |
| 10–18 | 11 | 18 | 27 | 43 | 110 |
| 18–30 | 13 | 21 | 33 | 52 | 130 |
| 30–50 | 16 | 25 | 39 | 62 | 160 |
| 50–80 | 19 | 30 | 46 | 74 | 190 |
| 80–120 | 22 | 35 | 54 | 87 | 220 |
| 120–180 | 25 | 40 | 63 | 100 | 250 |
| 180–250 | 29 | 46 | 72 | 115 | 290 |
Over the smaller size, up to and including the larger: 30 mm is in the range 18–30, 30.01 mm in 30–50. A value is given only where two published tables agree; combinations two tables do not agree on are left out (for the classes in this finder the tables agreed). The limits of a class follow from its fundamental deviation, from ISO 286-1, and the tolerance of its grade; for the r6 and s6 shafts above 50 mm the fundamental deviation changes inside the range (50–65, 65–80 and so on), and the finder uses those steps.
Every grade and fundamental deviation here appears in two published tables of ISO 286, and every class the finder gives was checked against a published table of limit deviations; a value two tables do not agree on is left out. Sizes up to 3 mm and above 250 mm, and other classes, are not in this finder.
A nominal size of 40 mm with the hole to class H7 and the shaft to class g6. The capital letter is the hole, the small letter the shaft; the letter places the zone against the nominal size and the number is the tolerance grade. To ISO 286, 40 H7 is 40.000 to 40.025 mm and 40 g6 is 39.975 to 39.991 mm, so the fit has a clearance of 9 to 50 micrometres.
In a clearance fit the shaft is never larger than the hole within the limits, so the parts slide or turn in each other. In an interference fit the shaft is never smaller than the hole, so the parts are pressed together. In a transition fit, such as H7/k6 or H7/js6, the actual sizes decide: the pair may have a small clearance or a small interference. Which fit a part needs is set by its drawing or its maker.
Measure the shaft with a micrometer and the bore with a bore gauge, in several places along it and in two directions at right angles, and enter the reading in the measured field. The finder says whether it is inside the zone of the class on the drawing and, if not, how many micrometres above the upper limit or below the lower limit it is.
Nominal sizes over 3 mm up to and including 250 mm; the hole classes H6, H7, H8, H9, H11, F7, G7, K7, M7, N7 and P7; the shaft classes e8, f7, g6, h6, h7, h9, h11, js6, k6, m6, n6, p6, r6 and s6. A size of exactly 30 mm is in the range 18 to 30 mm, 30.01 mm in 30 to 50 mm. Other sizes and classes are in ISO 286-2.
The nominal size with the fit or class as on the drawing (40 H7/g6), the drawing or a sketch with the other sizes, the material, the quantity, whether the mating part is renewed as well, and a photograph of the old part beside a ruler.
Limits of size are a cross-check of the drawing, not a part selection. Attach the drawing or a sketch with your measurements, and Vessel Core checks them before an offer goes back.
