Precision Ball Screw with Unfinished Shaft Ends
This type of ball screw is mass produced by cutting standardized screw shafts of precision ball screws to fixed lengths. The shaft ends can easily be modified with additional machining.
To meet various intended purposes, THK offers several ball screw models with different types of nuts: the single-nut type (Model BNF), the offset preload-nut type (Model BIF), and miniature ball screws (models MDK and MBF).
Types
Highlight feature tags
- Compact
- Miniature
- Screw shaft end additional machining
- Preload
- No preload
- Offset preload
- Return-pipe type
- Deflector type
- Precision positioning (ball screw)
- Precision positioning (ball screw)
- Screw shaft end additional machining
- Preload
- Offset preload
- Return-pipe type
Screw shaft diameters (mm) : 16,18,20,25,28,32,36,40,50
- Precision positioning (ball screw)
- Screw shaft end additional machining
- No preload
- Return-pipe type
Screw shaft diameters (mm) : 16,18,20,25,28,32,36,40,50
- Precision positioning (ball screw)
- Screw shaft end additional machining
- No preload
- Compact
- Miniature
- Deflector type
Screw shaft diameters (mm) : 04,06,08,10,12,14
- Precision positioning (ball screw)
- Screw shaft end additional machining
- No preload
- Compact
- Miniature
Screw shaft diameters (mm) : 04,06,08,10,12,14
Features
Structure and Features
This type of ball screw is mass produced by cutting standardized screw shafts of precision ball screws to fixed lengths. The shaft ends can easily be modified with additional machining.
To meet various intended purposes, THK offers several ball screw models with different types of nuts: the single-nut type (Model BNF), the offset preload-nut type (Model BIF), and miniature ball screws (models MDK and MBF).
Contamination Protection
Nuts of the following model numbers have a labyrinth seal attached.
- All variations of models BNF and BIF
- Model MDK0802/1002/1202/1402/1404/1405
When it is possible that dust or foreign material may enter the nut, it is necessary to use a contaminaton protection device (e.g. bellows) to completely cover the ball screw.
Lubrication
Ball screw nuts are sealed with lithium soap-based grease at shipment.
(Models MDK and MBF only have an anti-rust oil applied.)
Additional Machining of the Shaft End
Since only the effective thread of the screw shaft is treated with induction hardening (all variations of models BNF and BIF and Model MDK 1405) or carburizing (all variations of Model MBF and models MDK0401 to MDK1404), the shaft ends can easily be modified with additional machining, either by grinding or milling.
In addition, since both ends of the screw shaft have a center hole, they can be cylindrically ground.
| Surface hardness of the effective thread | : 58 HRC to 64 HRC |
| Hardness of the screw shaft ends | |
| All variations of models BNF and BIF, Model MDK 1405 | : 22 HRC to 27 HRC |
| All variations of Model MBF, Model MDK0401 to MDK1404 | : 35 HRC or less |
THK has standardized the shaft end shapes of the screw shafts in order to allow speedy quotation and manufacturing of ball screws.
The shapes for shaft ends include Models H, K, and J, which allow standard Support Units to be used. See Ball Screw Peripherals: Support Unit for more information.
Nut Types and Axial Clearance
|
Screw shaft outer diameter (mm) |
ø 4 to ø 14 |
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|---|---|---|---|---|
|
Nut type |
Model MDK |
Model MBF |
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 |
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Accuracy grades |
C3, C5 |
C7 |
C3, C5 |
C7 |
|
Axial clearance (mm) |
0.005 or less (GT) |
0.02 or less (G2) |
0.005 or less (GT) |
0.02 or less (G2) |
Note: The notation in the parentheses indicate the axial clearance symbol.
|
Screw shaft outer diameter (mm) |
ø 16 to ø 50 |
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|---|---|---|---|---|
|
Nut type |
Model BIF |
Model BNF |
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 |
 |
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|
Accuracy grades |
C5 |
C7 |
C5 |
C7 |
|
Axial clearance (mm) |
0 or less (G0) |
0 or less (G0) |
0.01 or less (G1) |
0.02 or less (G2) |
Note: The notation in the parentheses indicate axial clearance code.
