Automotion Components Tolerance Rings
What is...
Features
Advantages
- Rapid, low cost assembly.
- Relaxes machining tolerances.
- High torquw capabilities.
- Elminiateds use of keyways, pins, etc.
- Absorbs vibrations.
- Eliminates problems of different thermal expansion of mating parts.
Applications
A huge range of applications:
- Fixing device for handles, knobs, rings or bushes.
- To mount roller bearings.
- Where defined forces need to be transmitted such as mounting of pulleys, fly wheels, fans etc.
Hole system:
Used when a standard nominal bore diameter is specified (hole basis system).
The tolerance ring is placed over the shaft and the shaft is pressed into place.
The flat edge is on the inside of the ring.
Shaft System:
When a standard nominal shaft diameter is specified (shaft basis system).
The tolerance ring is placed in the bore with the flat edge on the outside of the ring.
The rolerance ring is made in a slightly open condition which allows it to grip the bore surface during assembly.
Shaft System:
A special curved type of series AN (shaft basis system) for mounting of smaller roller bearings.
Materials
BN rings up to diameter 11,9mm are normally made from carbon steel, the bigger sizes from stainless steel.
AN rings up to diameter 15,9mm are normally made from carbon steel, the bigger sizes from stainless steel.
The series AL rings are exclusively made from stainless steel - carbon steel on request.
The majority of tolerance rings are made from stainless spring steel strip to provide better thermal and chemical resistance.
The smaller sizes of tolerance rings are usually made from carbon spring steel strip.
The capacity i.e. the transferable torque and the radial load of the carbon steel Tolerance rings is slightly higher than tolerance rings made from stainless steel.
Stainless steel: The spring qualities of the tolerance ring does not deteriorate when operating at continuous temperatures of up to 250oC or when exposed to 300oC for brief periods.
Carbon steel: The spring qualities of the tolerance ring does not deteriorate when operating at continuous temperatures of up to 120oC or when exposed to 170oC for brief periods.
The diagram shows the mounting of a roller bearing 6204 with an outside diameter of 47mm in an aluminium housing. The assembly force of 2300N is necessary for a J6 fit. When roller bearings are mounted without the tolerance ring AN47-508 the acial retenstion force falls to zero at a temperature of 80oC, whereas using a tolerance ring AN47-508 there is still an axial retention of 1100N at a temperature of 120oC.
General Guidance
Shaft and Bore Tolerances
The limits chosen for the diameters of shaft and bore determine the fit between the two elements and hence the holding capacity of the whole assembly. The required dimensions can be taken from the table of available tolerance ring sizes.
With this in mind, please note the following points:
- Tolerances according the ISO system are permissable up to h9 for shafts and H9 for bores and under certain conditions up to h11 or H11.
- The tolerances quoted for the mounting of roller bearings and for torque transfer refer to the combinations of steel on steel or steel on many non-ferrous metals. They apply to the temperatures up to 100oC.
Applications should be tested if they involve materials that differ considerably from steel in their strength properties.
Details for Mounting Ball Bearings
The use of tolerance rings mounting roller bearings has become more and more widespread in industry. Both, the two standard types BN and AN and the type AL (speciall developed for the mounting of ball bearings) can be used for this purpose. The use of tolerance rings to mount roller bearings allows wider machining tolerances and thus saves money by reducing rejects.
Mounting of tolerance rings in the "centered" or "piloted" arrangement is preferable in this application. In order to take advantage of the compensation for different thermal expansion, for instance between light alloy housings and steel bearings offered by tolerance rings, suffix B3 roller bearings with larger than normal clearances should be used, as the relatively high radial pressure required for mounting of the bearing tends to reduce the clearance between bearing and shaft.
Installation
Selecting the mounting arrangement
"Free" Arrangement:
This arrangement is extremely economical because the ring is simply placed between the straight cylindrical surfaces of the bore and the shaft. If this arrangement is used the assembly may be slightly off-center, an allowance must be made for a reduction of about 20% in the torque M given in the tables
"Free" arrangement AN
"Free" arrangement BN
"Centered" Arrangement:
The centered arrangement is used when perfect concentricity is required or major radial impact loads are to be expected. Selection of the approriate fit between shaft and bore keeps eccentricity within the required tolerance limits, at the same time providing shock absorbtion to protect the toerance ring from damage.
"Centered" arrangement AN
"Centered" arrangement BN
"Piloted" Arrangement:
The piloted arrangement is necessary where concentricity is critical or where the tolerance ring will rotate with respect to applied radial load.
"Piloted" arrangement AN, AL
"Piloted" arrangement BN
Tandem Mounting of Tolerance Rings:
Where an application requires a greater load than that provided by one tolerance ring, it is, of course; possible to fit two or more tolerance rings until the sum of their load ratings exceeds the load to be carried.
It is necessary that the rings to be used, are separated by flanges to avoid the rings slipping over each other.
Tandem mounted AN
Tandem mounted BN
Mounting Instructions
Centered arrangement, type BN
Tolerance ring is placed in the shaft groove. The shaft together with the tolerance ring s then pressed into the bore.
Free arrangement, type BN
The tolerance ring is placed over the shaft and an assembly tool is used to brace the ring as the shaft is pressed into place.
Centered arrangement, type AN
The tolerance ring is placed in the housing and then the shaft is pressed into the bore, at right angles to the groove.
Free arrangement, type AN
The tolerance ring is placed in the bore and a bed plate is used to support it while the shaft is pressed into place.
The illustration shows a ventilation fan being secured to a shaft using a tolerance ring. A secondary function of this design is, that the fan is securing the axial position of the roller bearing.
In this illustration ball bearings are mounted with a tolerance ring in the feed mechanism of an industrial sewing machine.
Here a pump wheel is fastened into a drainage and condesation pump by means of a tolerance ring.
The rotor of a variable condensor, insulated in a ceramic bush, is retained by a tolerance ring.
Tandem-mounted tolerance rings on a mowing machine drive.
Roller bearings are mounted in a fluid drive with type AN tolerance rings. In this application max. operating temperatures of 170oC are reached.
