Top Adv

Shrink Fit: Shrink fit (transverse press) is the non-forcible inserting of the part after previous hole heating or after shaft cooling. In case of shrink fit, the effective interference also decreases to a certain level due to "subsidence". The decrease, however, is significantly smaller than in the case of force fit. The value of subsidence depends on the roughness of the connected areas. The loading capacity of shrink fit coupling is approximately 1.5 times higher than in the case of force fits. The selection of heating or cooling depends on dimensions of the parts and technical possibilities. During the hole heating, it is necessary to observe that the temperature when structural changes in material occur (in case of steel, it is approximately 200C/395F to 400C/750F) is not exceeded. Heating of outer parts is usually done in a oil bath (up to 150C/300F) or gas or an electric furnace. Parts with small diameters have to be heated to a much higher temperature than ones. Cooling of shafts is usually done rather with smaller couplings, using carbon dioxide (-70C/-95F) or condensed air (-190C/-310F). For couplings with large assembly interferences, a combination of both methods may be used. Shrink fitting is unsuitable for parts made of heat-treated steel and in case of a heated part fitted on a hardened one. In such case, it is necessary to cool the inner part or force fit the coupling.

Preferred Renard Numbers For American National Standard (ANSI Z17.1-1973, ISO 3-1973)

Preferred Numbers are a serious of selected numbers for use to standardize purposes in preferences in any other numbers. These numbers are created by Charles Renard. These system was adopted as ISO 3-1973, ANSI Z17.1-1973 and British Standard BS2045:1965. He discovered that 425 different sizes of cable were being used to moor the balloons, a logistical nightmare, and set about determining how best to reduce these to a smaller number of sizes. After He determined  that the relevant characteristic of the cable was its mass per unit length ( Such as  diameter, Lengths, volume, areas etc.) Renard succeeded in replacing the 425 sizes with 17 sizes that covered the same range. These preferred numbers of serious also would help ratings of machinery and apparatus in kilowatts, horsepower, voltages, etc. These number can be used in Metric, inch or any other customary units.

The Renard Numbers are five geometric sequence. A geometric sequence takes this form:

For Rn, Hence: 10b/n,10b/n, 10b/n, 10b/n,10b/n

where "a" is the scale factor and n ≠ 0 is the common ratio, where "b" is an integer in the serious 0,1,2,3, etc. Renard Preferred Numbers are called the R5, R10, R20, R40 and R80 series.

Renard Series Numbers, Rn, where a = 1 and r = ax10b/n. For each series, values are calculated from 1 to 10, and then rounded. As an example, If n=5, and a=1 ( to round the number "a" can be taken 10) so Rn can be calculated as followed;

For R5, Hence: 100/5 = 1, 101/5 = 1.584... ~ 1.6, 102/5 = 2.511... ~ 2.5, 103/5 = 3.981... ~ 4.0, 104/5 = 6.309... ~ 6.3, 105/5 = 10

Renard Series Number shown in the chart below( for R5, R10, R20, R40 and R80);

Renard Series DesignationPrefered Numbers
R5: 1.001.602.504.006.30

Some rounded values are desirable to use in some application, it depends on how high accurate or less accurate numbers wanted. For less accurate number, it can be chosen by using one prime ( R' ) or two prime ( R" ) of the Renard numbers. For example;

R10': 1.0 , 1.3 , 1.6 , 2.0 , 2.5 , 3.2

R10": 1 , 1.2 , 1.5 , 2 , 2.5 , 3

ANSI Preferred Metric Sizes B4.2-1978, ANSI B32.4-1974

ANSI preferred basic sizes of mating parts should be selected from the first choice sizes as shown in the chart below. These sizes shown in the chart below have been selected from the preferred round diameters of the metal products in ANSI B32.4-1974 Round, Square and Hexagonal Metal Products for Preferred Metric Sizes. The first choice sizes given in the chart below follow approximately the R10 preferred series of numbers where succeeding numbers in the series increments of 25%.The Second choice preferred number series shown in chart below selected from R20. These preferred number series may be converted to sizes in several ways. Often they are multiplied or divided by some multiple of ten (e.g.,1.0, 1.6, 2.5, 4.0, 6.3, 10; 1000, 1600, 2500, 4000, 6300, 10000.). In the chart below the preferred numbers have multiplied by 1000.

1st Choice2nd Choice1st Choice2nd Choice 1st Choice2nd Choice
- 2.2-28-350
-2.8-35- 450
3-40- 500-
-3.5-45- 550
5-60- 800-
6-80- 1000 -

Untitled 1

Home | Mechanical Engineering| Robot | Aerospace | Structural Engineering |Videos | Comment |