Couplings Bore and Keyway Additional Modification Service

Bore Additional Modification [BT]

  • Coupling bores can be additionally modified. Bore diameters can be specified in 0.001 mm increments.
  • For bore diameters D1 and D2, specify the standard bore diameter for each product from minimum diameter to maximum diameter. *1
    *1: For standard and maximum bore diameters, see each product page. For disk type, the bore diameters listed in the "Disk Type Bore Diameters Available" below can be specified with this service. For bore diameters outside the range, please contact our customer service.
  • Combination with the keyway additional modification KT is also possible.*2
  • *2: The bore diameters listed in the "Keyway Additional Modification Applicable Bore Diameter List" are available for the service.
  • Additional modification is also available for inch size bores. For inch size bore diameters, refer to the table below and specify in millimeter increments.
inch mm
1/8   3.175
3/16   4.763
1/4   6.35
5/16   7.938
3/8   9.525
7/16 11.113
1/2 12.7
9/16 14.288
5/8 15.875
11/16 17.463
3/4 19.05
・When converting values into millimeters, round up the 4th digit after the decimal point.
inch mm
13/16 20.638
7/8 22.225
15/16 23.813
1 25.4
1-1/8 28.575
1-1/4 31.75
1-3/8 34.925
1-1/2 38.1
1-5/8 41.275
1-3/4 44.45
2 50.8


Please note.

  • For disk type bore diameters, specify from the available bore diameter range in the table below.
Unit:mm
Disk Type Bore Diameters Available
D1・D2
  3   4   4.5   5   6   6.35   7   8   9
  9.525 10 11 12 13 14 15 16 17
18 19 20 22 24 25 28 30 32
35 38 40 42 45 50      
・For bore diameters D1 and D2, specify the standard bore diameter for each product from minimum diameter to maximum diameter.
・Disk type specifiable bore diameters are regularly added.

[BT] Target products

  • Coupling category products are targeted.
Type Target Products
High-gain Rubber XGT2 XGL2 XGS2 XGT XGL XGS        
Vibration-Absorption Capable*1 XGHW                  
Disc*2 XHW XHS XBW XBS XBWS XBSS MDW MDS MHW MHS
Slit MSX MST MWS MSTS MWSS        
Jaw MJC                
Cross Joint XUT                  
Oldham MOR MOL MOS MOP MOM MOHS        
Bellows MFB MFBS                
Serration MSF                
Rigid*3 MRG MLR MRGS MLRS            

・Please contact our customer service for the price and delivery time of MJB MWBS XSTS XWSS XRP.
*1: Bore additional modification is only performed on the D1 side for The vibration-absorption capable disk type XGHW.
*2: For disk type bore diameters D1 and D2, specify from the disk type available bore diameter range table.
*3: MRG-W MRGS-W MLR-V MLRS-V are not available.


Part Number Specification

Specify the modification symbol BT after the bore diameter to be modified.
Combination with the keyway additional modification KT *1 is also possible.
*1: The bore diameters listed in the "Keyway Additional Modification Applicable Bore Diameter List" are available for the service.

Additional modification of keyway [KT][KA]

  • Couplings can be additionally modified with new JIS keyways based on JIS B 1301.
  • Metric or inch keyways can be selected with the modification symbol.
    [KT] Metric Keyway Modification (JIS Standard)
    [KA] Inch Keyway Modification (AGMA Standard)
  • The bore diameters listed in the "Keyway Additional Modification Applicable Bore List" in the table below are available for the service.
  • Keyway additional modification is available for both single-side only and double-side.

    As high-gain rubber and rigid types have the same bore diameter on both sides, keyway modification is available for double-side only.

  • Combination with the bore additional modification BT is also possible.

[KT] [KA] Target products

Type Target Products
High-gain Rubber XGT2 XGL2 XGS2 XGT XGL XGS        
Vibration-Absorption Capable*1 XGHW                  
Disc XHW XHS XBW XBS XBWS XBSS MDW MDS MHW MHS
Jaw MJC MJS                
Cross Joint XUT                  
Oldham MOR MOL MOS MOP MOM MOHS        
Bellows MFB MFBS                
Serration MSF                
Rigid*2 MRG MLR MRGS MLRS            
  • Please contact our customer service for the price and delivery time of MSX MST MSTS MWS MWSS MWBS XSTS XWSS.
  • We also offer keyway additional modification not listed in the catalog. Please contact our customer service.
  • *1: Keyway additional modification is only performed on the D1 side for The vibration-absorption capable disk type XGHW.
    *2: Rigid Type MRG-W MRGS-W MLR-V MLRS-V is not targeted.

    Keyway Modification metric


  • Keyway Additional Modification Applicable Bore Diameter List
  • unit:mm
    Applicable Bore Diameter
    D1D2
    Keyway Key
    b t Nominal Dimension
    b×h
    Standard Dimension Allowance
    (JS9)
    Standard Dimension Allowance
    6 7       2 ±0.0125 1.0 +0.1
    0
    2×2
    8 9 10     3 1.4 3×3
    11 12       4 ±0.0150 1.8 4×4
    13 14 15 16 17 5 2.3 5×5
    18 19 20 22   6 2.8 6×6
    24 25 28 30   8 ±0.0180 3.3 +0.2
    0
    8×7
    32 35 36 38   10 3.3 10×8
    40 42 44     12 ±0.0215 3.3 12×8
    45 48 50     14 3.8 14×9

    Excerpt from JIS B 1301

    ・The service does not cover keyway additional modification for bore diameters not listed in the table. Please contact our customer service.

    Keyway Modification inch

    unit:inch
    Standard Inch Bore Diameter
    D1D2
    Keyway
    Wk T
    Standard Dimension Allowance Standard Dimension Allowance
    1/2 1/8 +0.002
      0
    0.560 +0.01
      0
    9/16 1/8 +0.002
      0
    0.623 +0.01
      0
    5/8 3/16 +0.002
      0
    0.709 +0.01
      0
    11/16 3/16 +0.002
      0
    0.773 +0.01
      0
    3/4 3/16 +0.002
      0
    0.837 +0.01
      0
    13/16 3/16 +0.002
      0
    0.900 +0.01
      0
    7/8 3/16 +0.002
      0
    0.964 +0.01
      0
    15/16 1/4 +0.002
      0
    1.051 +0.01
      0
    1 1/4 +0.002
      0
    1.114 +0.01
      0
    1-1/8 1/4 +0.002
      0
    1.241 +0.01
      0
    1-1/4 1/4 +0.002
      0
    1.367 +0.01
      0
    1-3/8 5/16 +0.002
      0
    1.518 +0.01
      0
    1-1/2 3/8 +0.002
      0
    1.669 +0.01
      0
    1-5/8 3/8 +0.002
      0
    1.796 +0.01
      0
    1-3/4 3/8 +0.002
      0
    1.922 +0.01
      0

    Excerpt from AGMA standards

    Part Number Specification

    Specify the modification symbol KT after the bore diameter with the keyway to be modified.
    Combination with the bore additional modification BT is also possible.

    Price・Delivery

    • Please feel free to contact us.

    Customer Service

    • Usage Method
    • Technical Question
    • Customization Products

    NBK America LLC

    9:00 to 17:00 on weekdays, Eastern Standard Time