Page 1675 - MiSUMi 2025

3. Axial Clearance of Ball Screws
Axial clearance is not the main factor affecting positioning accuracy during unidirectional feed. However, when the feed direction or axial
load is reversed, it acts as backlash and affects positioning accuracy. Please select the axial clearance of the ball screw according to the
required positioning accuracy.
Q Types of Rolled Ball Screws Q Types of Precision Ball Screws
Accuracy Screw Lead Screw Shaft Length(mm) Axial Clearance Accuracy Screw Lead Screw Shaft Length(mm) Axial Clearance
grade Type shaft dia. (mm) min. max. (mm) grade Type shaft dia. (mm) min. max. (mm)
08 02 100 400 08 02 210
02 02 100
10 600 10 315
04 0.05 or less 04 0.008 or less
04 04
12 500
12 05 800 10
10 150 05 150
05 15 10
C5 C－KBS
10 0.1 or less 20
15 1200
16 05
C－TBSE
C7 20 20 10 200 900 0.015 or less
C－TBSB
05 20
20 10 0.15 or less 05
20 25 10 300
200
05 25
25 10 2000
25
0.2 or less
05
32 10 300
32
Selection Example of Lead Accuracy Selection Example of Axial Clearance
<Requirements> <Requirements>
· Ball screw diameter F15, lead 20. · Ball screw diameter F15, lead 5.
· Stroke 720mm · Allowable backlash Ú0.02mm
· Positioning accuracy Ú0.05mm/720mm <Selection Details>
<Selection Details> When the screw shaft diameter is F15, C5 grade with axial clearance
Select an appropriate lead accuracy grade based on the application below 0.015mm can meet the condition of allowable backlash amount
requirements. Ú0.02mm.
(1) Evaluating the screw thread length
Stroke＋Nut Length＋Margin＝720＋62＋60＝842mm
* The Margin shown above is an safety overtravel allowance, and
normally determined as 1.5～2 times the screw lead.
Lead 20×1.5×2 (both ends)=60
(2) Evaluating the lead accuracy
P.B-029 Table 1. is referenced and an Representative Travel
Error ±ep for 842mm ball screw thread.
C5 · · · Ú0.040mm/800～1000mm
(3) Determining the lead accuracy
It can be determined that a C5 grade (Ú0.040/800～1000mm)
ball screw can satisfy the required positioning accuracy of
Ú0.05/720mm.

B-030