BRONZE/IRON SINTERED BUSHINGS
Sintered self-lubrifiing bearings are obtained with the most modern and advanced processes in the field of powder metallurgy, presenting high mechanical and technological characteristics. They have a controlled porous structure and are impregnated with oil that is released gradually during regular operation forming a self-clarifying film. Lubricating oil can be replaced in whole or in part with graphite which gives the product a slightly drier and darker look. The useful porosity is 25-30% of its volume and is filled with chosen oil but can be lowered up to 18% in order to increase its mechanical strength in the case of very high static loads. The carefully mixed powders are pressed and printed and then sintered in the oven, at a temperature lower than the melting point, atmospheric and controlled temperature. Then after the calibration phase on the internal and external diameters, through an vacuum process the porosity of the parts are saturated with oil. Finally, sintered products can be protected with galvanic, burnished or steam-oxidized coatings or subjected to heat treatments. They are available in cylindrical and flanged format.
Any mechanical processing is inadvisable because it would change its surface structure preventing the oil from escaping. However, if a processing cannot be avoided, it is recommended to use hard metal tools of the same quality used for cast iron processing, perfectly sharpened with front and side strip of about 7°, working with small passes and small feeds at a speed of 100m/min'.
Sintered bushings offer many advantages such as:
• are self-lubricating and free from external maintenance and lubrication
• good friction properties with very high creeping speed
• even complex drawing parts ready for assembly can be obtained
• the low cost of production makes the product very economical
• they are generally suitable where there are many turns and few loads.
Assembly shall be carried out by interference in the seat by means of a spindle with shoulder and rectified surface to avoid damage to the bushing. Finally, an anti-slip extractor is required to allow spindle extraction. The spindle tolerance should be maintained in the m5 field.
Sintered bronze has the following standard construction tolerances:
- Ø external r7
- Ø internal F7 (when the tolerance has been mounted it will result in G7)
- length h js13 assembly standard:
- housing H7
The shaft must have a hardness possibly between 200 and 300 HB, a roughness between 0.2 and 0.8 μm and a tolerance between f7 and f8.
Series “BZ”.. ( BRONZE)
Series “BZ” means self-lubricating bushings in sintered bronze.
Normally this product is supplied impregnated with oil but on request it is available with a graphite percentage.
The graphite is a lubricant material which allows a better fluidity even at low rpm. It reduce lightly the load capacity compared to other lubricants but this depends on the percentage used.
This type of bushing is not suitable to work in dusty environments.
This bushings can be used in various applications such electric motors of small size, agricultural machinery, automation in general, food machinery, pharmaceutical, packaging and office machinery (that is in printers, photocopiers, paper cutters, etc ...)
Series “FE”.. (IRON)
Series “FE” means self-lubricating bushings in iron sintered.
This type of bushing compared to those in bronze are suitable to withstand even higher loads.
The product must not remain in contact with the water. It must avoid blows during the handling and we advise against the reuse.
Their use is very large because it can be used in industrial machinery, machines tools, textile and agriculture sector , chemical and automotive industry.
Bushings must be stored in a dry and dust-free environment. It is absolutely necessary to avoid putting them in contact with substances capable of exerting an absorbent action such as: paper, cardboard, wood, etc..