Advanced Technology of “Miniature”
洗練されたミニチュアの技術
Q-BS-16
Q&A
Question: Is an Axial play the same as backlash?
Axial play of Ball Screws is often called Backlash.
It is no problem for actual use, but it is not
accurate.
Usually, Ball Screws are assembled with small
clearance between Shaft and Nut groove.
We call this Axial play （see figure right）.
Axial play
If Ball Screws receive Axial load, groove of Shaft and Nut contact to Ball, after that the Elastic
displacement will appear on the contact surface. Total of initial clearance（Axial play）and Elastic
displacement becomes Backlash（see figure below）.
Initial Clearance +Elastic +displacement
12
Shaft dia.：φ14
Lead：3mm
9
6
3
0
Initial clearance : 3μm
0
100
200
300
400
500
600
700
Axial load（N）
To be more accurate, it is necessary to add Elongation by heat generation or deformation by
torsion. But they can be disregarded in case of Miniature Ball Screws.
To be exact, Axial play is different from Backlash!!!
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