Engineering Data of Mounted Units

1. Features of LDK Ball Bearing Units

LDK ball bearing units consist of inserts and housings,based on the methods of mounting the units to shafts, they can be divided into four types:the setscrew locking type,the adapter sleeve locking type,the eccentric  locking collar type and the concentric locking collar type.

The housings have five types:Cast gray or ductile iron housings,pressed steel housings,thermoplastic housings,stainless steel housings and Zinc alloy die casting housings.

Spherical outside surface self-aligning ball bearing units are compact in design with perfect sealing devices. All LDK ball bearing units have contact-type seals at both sides.The seals will vary according to the different types of bearings.By selecting the sealing devices,which is most suitable to the application and working condition,long bearing life can be guaranteed.

Sealing Devices:

(Table 1)

2. Ball Bearing Inserts

The spherical outside ball bearing inserts are sealed at both sides.The internal structure dimensions,chromium bearing steel balls and retainers are same as those of the deep groove ball bearings.

2.1 Material of Bearing Rings and Balls.

LDK'S insert ball bearings are available with material of Chromium steel and stainless steel.

• 2.1.1 Gcr15 Chromium Bearing Inserts

The bearing rings and balls are made of GCr15 chromium bearing steel of which the chemical composition are shown in table 2.

(Table 2)

The Rockwell hardness forbearing rings are HRC59-65,for balls are HRC61-66,with high wear resistance and contact fatigue strength.For the inner ring of the setscrews type bearings,the hardness of the setscrews hole zone on the extended ends are less than HRC50 after annealing(CSB,SER,SB,CSB series).

The inner rings of setscrews type bearings are special heat treated by the induction heating method.Therefore, the raceway of the inner ring is hardened completely through the ring, while the setscrews hole zone on the extended ends of the inner rings are softened (as indicated in drawing).

The bearings have two hardened setscrews with threads which are installed in the soft extension of the inner ring, thread contact is thereby attained for maximum holding power,since they can be sufficiently tightened without causing inner ring cracking.

This special heat treatment ensures the most efficient bearing performance and prevents the setscrews from loosening during operation.

• 2.1.2 Material of Stainless Steel Bearing Inserts

The bearing rings and balls are made of SUS440 equivalent stainless steel of which the chemical composition are shown in Table 3.

(Table 3)

For material of components of stainless steel insert bearings, please see table 4.

(Table 4)

2.2  Bearings Tolerances

• 2.2.1   Outer Rings Toleraces

The outer rings tolerances,which are shown in Table 5,are the same as those for deep groove bearings.

Table 5.  Outer rings tolerances (μ  m)

Notes:

• △Dmp=the deviation of a single plane mean

• outside diameter of the outer ring.

• Kea=Radial run out of assembled bearing outer ring.

• D=Nominal outer ring outside diameter.

• 2.2.2 Inner Rings Tolerances

The inner rings tolerances are different from those of deep groove bearings.The values are shown in Table 6 and Table 7.

1)Tolerances for cylindrical bore bearing inner rings

Table 6.   Cylindrical bore inner rings tolerances  (μm)

Notes:

• d=Nominal bore diameter
  

• △dmp=The deviation of a single plane mean bore diameter of the inner rings

• Kia=Radial run out of assembled bearing inner ring

• △Bs=The deviation of a single width of inner ring

2)Tapered  Bore  Inner  Rings  Tolerances

Table 7.Tolerances on inner rings of tapered bore bearings  (μm)

Notes:

• d=Nominal bore diameter

• d₁=Theoretical diameter of larger end of tapered bore d₁ is obtained by following formula: is obtained by following formula: d=d+0.083333 B

• B1=Nominal inner ring width

• θ=The nominal taper angle=2° 23' 9.4"=2.38594°

• △dmp =Variation of tolerance of average bore diameter in plane at theoretical small end of tapered bore.

• △d1mp=Variation of tolerance of average bore diameter in plane at theoretical large end of tapered bore.

• △d1mp -△dmp =Variation of tolerance of average bore diameter in planes between theoretical small and large end of tapered bore.

• 2.2.3   Chamfer Dimensions for Inner Ring

Table 8   Chamfer dimension limits  (mm)

• 2.2.4  Tolerances  for Distance ''S'' From Center Line of Outer Ring to Side of Inner Ring

Tolerances for distance ''S'' between the radial plane passing through center of spherical surface of outer ring and a side of inner ring are shown in table 9.

Table 9

2.3  Radial Internal Clearance of Bearings

The radial internal clearance for the spherical outside surface ball bearings is usually greater than that of the same sizes of deep groove ball bearings.The clearance for the cylindrical bore bearings is shown in Table 10, while the clearance for the tapered bore bearings is shown in Table 11.

table 10.   Radial  internal clearance of cylindrical  bore bearings   (μm)

Table 11.    Radial internal clearance of tapered bore bearings    (μm)

Notes:  When the internal clearance of a bearing is measured,deformation occurs under loading,Therefore, to obtain the measuring value clearance,add the below correction clearance (see Table 12)to the radial clearance above.

table  12.

3. Bearing Housings

LDK's bearing housings are available with cast gray iron, cast ductile iron, Stainless steel, Thermoplastic, Stamped steel and Zinc Alloy steel.

3.1 Material of Housings

• 3.1.1 Material for Cast Iron Housings

The material for cast iron  housing is  HT200(gray iron)and  QT400/QT450(ductile iron)of  which  the  mechanical properties are shown in Table 13.

Table 13-(1).

Table 13-(2).

• 3.1.2 Material of Stainless Steel Housings

The material for Stainless Steel Housing is SUS304 Stainless steel of which the chemical composition are shown in following table 14.

Table 14.   (%)

• 3.1.3 Material of Zinc Alloy Housings

Zinc Alloy Die Casting

• 3.1.4 Material of Thermoplastic housings

The material for thermoplastic housing is mainly reinforced PBT or PA polymer.PP polymer is used for end  covers.

• 3.1.5 Material of stamped steel

Cold rolled steel sheet,surface with electroplating treatment.

3.2 Tolerances on spherical inside diameter of housing

Table 15.  Tolerances on spherical inside diameter of housing   (μm)

Notes

• Dam=(Da max+Da min)/2

  Damax_Da maximum measured value of Da.

  Damix_Da minimum measured value of Da.

• Dimensional tolerances for spherical inside diameter of housing are classified into H7 clearance fit, K7 for interference fit and J7 for intermediate fit between H7 and K7.

• When H7 fit is applied,the self-aligning bearings are equipped with locking-pins.

• 3.2.1 The fits between inserts and the housings

Under normal conditions,the fit between insert and housing,which can be supplied by us,is listed as follows: Table 16.

If not specified,J7 fit will be standard fit for LDK mounted ball bearing units.If other fit or starting torque requirement is required,please check with our sales.

• 3.2.2 Tolerances for Pillow Block Housings Center Height

Table 17.      (mm)

3.2.3   Tolerances for  Flange Type  Housings

Tolerances for Flange Type Housings are shown in Table 18.

Table 18.            (mm)

• 3.2.4 PFTD, FCT (RFB)

*Re-lube. Type  PFTD, FCT  Housings Available too.

(mm)

3.2.5 Tolerances for flange cartridge type housings

Tolerances for flange cartridge type housings are shown in Table 19.

Table 19.  (mm)

• 3.2.6 Tolerances for special type flange units

Tolerances for special type flange units are shown in Table 20.

(mm)

3.2.7 Tolerances for Cartridge Type Housings

Tolerances for Cartridge Type Housings are shown in Table 21.

Table 21.    (mm)

3.2.8 Tolerances for Take-up Type Housings

Tolerances for Take-up type  housings  are  shown  in  Table  22.

Table 22.   (mm)

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