iglide® M250 - Material data

Maximum surface speed

fpm	Rotating	Oscillating	Linear
Constant	157	118	492
Short-term	393	275	984

Permitted surface speeds

iglide® M250 is finished with greater wall thickness in the standard product range. As this lowers the conduction of frictional heat, the iglide® M250 bushings are mainly considered for low to medium surface speeds. The maximum permitted surface speeds in the dry operation are 157 fpm (rotating) and 393 fpm (linear) respectively.

Figure 4.3: Maximum recommended surface pressure dependent on the temperature

Temperatures

The short-term permitted maximum temperature is 338° F. The iglide® M250 bushings should however be exposed to this temperature only without any more load. The long-term permitted application temperature lies at 176° F. Here you'll find the wear limit, thus also the temperature at which the wear increases disproportionately.

Temperature limits

iglide® M250	Application temperature
Lower	- 40 °F
Upper, long-term	+ 176 °F
Upper, short-term	+ 338 °F

Figure 2.4: Coefficients of friction dependent on the surface speed, p = 108.75 psi

Friction and wear

The coefficient of friction µ of a bushing is, among other things, influenced by surface speed and load. If the load remains constant, the coefficient of friction rises with increasing speed (see Fig. 4.4)

In contrast, a lone increase of the load at constant speed results in a reduction of the coefficient of friction (see Fig. 4.5)

Friction and wear depend also strongly on the surface of the shaft. The most favorable surface finish of the shaft for iglide® M250 bushings is at Ra = 0.023622 in (0.6 mm), considering the coefficient of friction.

Coefficients of friction for iglide® M250 against steel
(Ra = 1 µm, 50 HRC)

iglide® M250	Dry	Fat	Oil	Water
Coefficients of friction µ	0.18 - 0.40	0.09	0.04	0,04

Fig. 2.7: Wear, rotating application with different shaft materials, load p = 108 psi, v = 98 fpm

Figure 4.8: Wear with various shaft materials in the rotating operation dependent on the load

Figure 4.9: Wear in pivoting and rotating applications at constant load with various shaft materials, p = 290 psi

Shaft materials

The diagrams 4.7 and 4.9 display a summary of the results of tests with different shaft materials conducted with bushings made of iglide® M250.

In rotations, the shaft material plays only a comparably minor role up to loads of 290 psi. Figure 4.7 shows at a glance the shaft materials best suited for low loads.

If the load increases, the wear of some pairings increases markedly. For this reason, a suitable shaft material should be considered with high loads. These are the hard shafts, for example Cf53 or hard-chromed shafts, if the wear resistance is viewed in isolation.

Figure 4.9 clarifies that the iglide® M250 is essentially better for rotating and pivoting operations. Here it must be mentioned that in practice the vibrations acting on the bushing are often extremely high in pivoting movements. Here the iglide® M250 can exercise its particularly dampening properties. In our test such vibrations are excluded, so that the comparison between rotation and pivoting operation amazes at first.

Important tolerances for iglide® M250 bushings according to ISO 3547-1 after the press-fit.

Diameter d1 [inch]	Shaft h9 [inch]	iglide® M250 D11 [inch]
Up to 0.019685	0 - 0.0009843	+0.0007874 + 0.0031496
> 0.1181 to 0.2362	0 - 0.0011811	+0.0011811 + 0.0041339
> 0.2362 to 0.3937	0 - 0.0014173	+0.0015748 + 0.0051181
> 0.3937 to 0.7087	0 - 0.0016929	+0.0019685 + 0.0062992
> 0.7087 to 1.1811	0 - 0.0020472	+0.0025591 + 0.0076772
> 1.1811 to 1.9685	0 - 0.0024409	+0.0031496 + 0.0094488

Installation tolerances

iglide® M250 bushings require relatively large bushing clearances for optimum performances. These ensure that the bushings remain reliable even with thermal expansion and water absorption.

These clearances, which would have been unacceptable for a metallic bearing, only enable the iglide® M250 plain bushing to display its best qualities such as wear resistance and freedom from maintenance. The disadvantages of the bushing clearance are again compensated by the vibration dampening properties.

After the installation in a housing bore with the tolerance H7, the inner diameter of the bushing automatically adjusts to the D11 tolerance. The shaft should have a minimum H9 tolerance.

Medium	Resistance
Alcohol	+ to 0
Hydrocarbons	+
Fats, oils, without additives	+
Fuels	+
Diluted acids	0 to -
Strong acids	-
Diluted bases	+
Strong bases	0

+ resistant      0 conditionally resistant      - non-resistant

Figure 4.10: Influence of humidity absorption of iglide® M250 bushings

Electrical properties

Specific forward resistance	> 1013 Ωcm
Surface resistance	> 1011 Ω

Chemical resistance

iglide® M250 bushings have a good resistance against chemicals. They are resistant to most lubricants. The iglide® M250 is not affected by most weak organic and inorganic acids.

The humidity absorption of iglide® M250 bushings amounts to about 1.4% in standard climatic conditions. The saturation limit in water is 7.5%. This should be considered according to application conditions.

Radioactive rays

Bushings made of iglide® M250 are conditionally usable under radioactive radiation. They are resistant up to a radiation intensity of 1,000 Gy.

UV-resistant

iglide® M250 bushings are permanently resistant to UV rays.

Vacuum

The iglide® M250 bushing degasses potentially available humidity in vacuum. The relatively high humidity absorption of the bushing therefore permits the bushing to be used in vacuum only restrictedly.

Electrical properties

Bushings made of iglide® M250 are electrically insulating.