1. Lead Accuracy Lead accuracy of HSK ball screw (grade Co-C5) is specified in 4 basic terms (E, e, e300, e2 ) There are defined in Fig.3.1 Tolerance of deviation (±E) and variation (e)of accumulated reference travel are shown in Table 3.2 and 3.3. 
Table 3.1 Definition of Terms for Lead Accuracy | Terms | Reference | Definition | Scope | | Travel Compensation | T | Travel compensation is the difference between specified and nominal travel within the useful travel. A slightly smallervalue compared to the nominal travel is often selected by the customer to compensate for an expected elongatino caused bu temperature rise or external load. Therefore"T" is usually a negative value. | | | Actual Travel | | Actual travel is the axial displacement of the nut relative to the screw shaft. | | | Mean Travel | | Mean travel is linear best fit line of actual.This could be obtained by the least quares method. This line represents the tendency of actual travel. | | | Mean Travel Deviation | E | Mean travel deviation is the difference between mean travel and specified travel within travel length | Table 3.2 | | Travel Variations | e
e300
e2
| Travel variaous is the band of 2 lines drawn parallel to the mean travel,on the plus and minus side. Maximum width of variation over the travel length. Actual width of variation for the length of 300mm taken anywhere within the tavel length. | Table 3.2
Table 3.3
Table 3.3 |
Table 3.2 Mean Travel Deviation (±E) and Travel Variation (e) (JIS 1192) unit:  m | Precision Grade | C0 | C1 | C2 | C3 | C5 | C7 | C10 | Travel Length
(mm) | Up | Down | ±E | e | ±E | e | ±E | e | ±E | e | ±E | e | e | e | | | 100 | 3 | 3 | 3.5 | 5 | 5 | 7 | 8 | 8 | 18 | 18 | ±50/300mm | ±210/300mm | | 100 | 200 | 3.5 | 3 | 4.5 | 5 | 7 | 7 | 10 | 8 | 20 | 18 | | 200 | 315 | 4 | 3.5 | 6 | 5 | 8 | 7 | 12 | 8 | 23 | 18 | | 315 | 400 | 5 | 3.5 | 7 | 5 | 9 | 7 | 13 | 10 | 25 | 20 | | 400 | 500 | 6 | 4 | 8 | 5 | 10 | 7 | 15 | 10 | 27 | 20 | | 500 | 630 | 6 | 4 | 9 | 6 | 11 | 8 | 16 | 12 | 30 | 23 | | 630 | 800 | 7 | 5 | 10 | 7 | 13 | 9 | 18 | 13 | 35 | 25 | | 800 | 1000 | 8 | 6 | 11 | 8 | 15 | 10 | 21 | 15 | 40 | 27 | | 1000 | 1250 | 9 | 6 | 13 | 9 | 18 | 11 | 24 | 16 | 46 | 30 | | 1250 | 1600 | 11 | 7 | 15 | 10 | 21 | 13 | 29 | 18 | 54 | 35 | | 1600 | 2000 | | | 18 | 11 | 25 | 15 | 35 | 21 | 65 | 40 | | 2000 | 2500 | | | 22 | 13 | 30 | 18 | 41 | 24 | 77 | 46 | | 2500 | 3150 | | | 26 | 15 | 36 | 21 | 50 | 29 | 93 | 54 | | 3150 | 4000 | | | 30 | 18 | 44 | 25 | 60 | 35 | 115 | 65 | | 4000 | 5000 | | | | | 52 | 30 | 72 | 41 | 140 | 77 | | 5000 | 6300 | | | | | 65 | 36 | 90 | 50 | 170 | 93 | | 6300 | 8000 | | | | | | | 110 | 60 | 210 | 115 | | 8000 | 10000 | | | | | | | | | 260 | 140 | | 10000 | 12500 | | | | | | | | | 320 | 170 |
Table 3.3 variation per 300mm (e300 )and Wobble Error (e2) (JIS B 1192) unit: m | Precision Grade | C0 | C1 | C2 | C3 | C5 | C7 | C10 | | e300 | 3.5 | 5 | 7 | 8 | 18 | 50 | 210 | | e2 | 2.5 | 4 | 5 | 6 | 8 | | |
2. Axial Play Accuracy grade and axial play of HSK's precision ball screws is shown in Table 3.4
Table 3.4 Combination of Accuracy Grade and Axial Play | Grade | P0 | P1 | P2 | P3 | P4 | | Axial Play | Yes | No | No | No | No | | Preload | No | No | Light | Medium | Heavy |
Guidelines for selecting Accuracy, Preload, Axial Play, Nut and Screw shaft3 | Accuracy | Preload and Axial Play | Nut Type | Screw shaft Type | | C10 | P0 (With Axial Play) | Single Nut | Rolled screw shaft | | C7 | P1 or P0
HSK standrd is P1 | According to the demand of customers | Rolled or Ground
(HSK standard is Ground) | | C5 | According to the demand of customers.If no idea, HSK standard is P2 | According to the demand of customers | Ground screw shaft with lead error inspection certificate | | C3 | According to the demand of customers.If no idea, HSK standard is P2 | According to the demand of customers | Ground screw shaft with lead error inspection certificate |
* Axial Play (P0)
Clearance in the Axial Direction of the Rolled and Ground Ball Screw unit: mm | Screw Shaft O.D. |
Rolled Ball Screw Clearance in the Axial Direction (Max.) |
Ground Ball Screw Clearance In The Axial Direction (Max.) |
 04 ~ 14 Miniature Ball Screw | 0.05 | 0.015 |
| 15 ~ 40 Middle Size Of Ball Screw |
0.08 | 0.025 |
| 50 ~ 100 Big Size Of Ball Screw |
0.12 | 0.05 |
* No Backlash and No Preload (P1)
* Spring Force of Light Preload (P2) | Model No | Spring Force(Kg)
Single Nut | Spring Force(Kg)
Double Nut | | 1605 | 0.1 ~ 0.3 | 0.3 ~ 0.6 | | 2005 | 0.1 ~ 0.3 | 0.3 ~ 0.6 | | 2505 | 0.2 ~ 0.5 | 0.3 ~ 0.6 | | 3205 | 0.2 ~ 0.5 | 0.5 ~ 0.8 | | 4005 | 0.2 ~ 0.5 | 0.5 ~ 0.8 | | 2510 | 0.2 ~ 0.5 | 0.5 ~ 0.8 | | 3210 | 0.3 ~ 0.6 | 0.5 ~ 0.8 | | 4010 | 0.3 ~ 0.6 | 0.5 ~ 0.8 | | 5010 | 0.3 ~ 0.6 | 0.8 ~ 1.2 | | 6310 | 0.6 ~ 1.0 | 0.8 ~ 1.2 | | 8010 | 0.6 ~ 1.0 | 08. ~ 1.2 |
3. Accuracy Definition as follow: (1) Periphery run-out of the supporting part of the screw shaft to the screw groove.
(2) Concentricity of a mounting portion of the shaft to the adjacent gound portion of the screw shaft.
(3) Perpendicularity of the shoulders to the adjacent ground portion of the screw shaft.
(4) Perpendicularity of the nut flange to the axis of the screw shaft.
(5) Concentricity of the ball nut diameter to the screw groove.
(6) Parallelism of the mounting surface of a ball nut to the screw groove.
(7) Total run-out of the screw shaft to the axis of the screw shaft. 
4. Preload Torque - Terms in relation to the preload torque generated during the rotation of the preload ball screws are shown in Fig.3.3
- Permissible ranges of torque variation rates is shown in Table 3.5
Table 3.5 Permissible ranges of torque variation rates Reference Torque
kgf·cm | Effective threading length (mm) | | Below 4000 | 4000 up 10000 | | Slenderness 1:below 40 | Slenderness 1:40 ~ 1:60 | - | | Grade | Grade | Grade | | Over | Incl. | C0 | C1 | C2, C3 | C5 | C0 | C1 | C2, C3 | C5 | C1 | C2, C3 | C5 | | 2 | 4 | ±35% | ±40% | ±45% | ±55% | ±45% | ±45% | ±55% | ±65% | - | - | - | | 4 | 6 | ±25% | ±30% | ±35% | ±45% | ±38% | ±38% | ±45% | ±50% | - | - | - | | 6 | 10 | ±20% | ±25% | ±30% | ±35% | ±30% | ±30% | ±35% | ±40% | - | ±40% | ±%45 | | 10 | 25 | ±15% | ±20% | ±25% | ±30% | ±25% | ±25% | ±30% | ±35% | - | ±35% | ±40% | | 25 | 63 | ±10% | ±15% | ±20% | ±25% | ±20% | ±20% | ±25% | ±30% | - | ±30% | ±35% | | 63 | 100 | - | - | ±15% | ±20% | - | - | ±20% | ±25% | - | ±25% | ±30 % |
Remarks:
1. Slenderness is the value of dividing the screws shaft outside diameter with the screws shaft threading length.
2. For reference torque less than 2kgf·cm, HSK specifications will apply. Glossary (1) Preload
The stress generated inside the screws when inserting a set of steel balls of one gage (Approximately 2) larger into the nut or using them on the 2 nuts which exercise mutual displacements along the screws axis in order to eliminate the gaps of the screw or upgrade the rigidity of the screw.
(2) Preload Dynamic Torque
The dynamic torque required for continuously rotating the screws shaft or the nuts under unload condition after the specified preload has been applied upon the ball screws.
(3) Reference
The targeted preload dynamic torque (Fig.3.3)
(4) Torque Vareation Values
The variation values of the targeted preload torque variation rates are specified generally based on JIS Standards as indicated in Table 3.5.
(5) Torque Variation Rate
The rate of variation values in relation to the reference torque.
(6) Actual Torque
The actually measured preload dynamic torque of the ball screws.
(7) Average Actual Torque
The arithmetic average of the maximal and minimal actual torque values measured when the nuts are exercising reciprocating movements.
(8) Actual Torque Variation Values
The maximal variation values measured within the effective length of the threads when the nuts are exercising reciprocating movements,the positive or negative values relative to the actual torque are adopted.
(9) Actual Torque Variation Rate
The rate of actual torque variation values in relation to the average actual torque. Calculation of reference torque Tp
The formula for computing reference torque of the ball screws is given in following:
 |  | | | Measurement Condition
The preload dynamic torque Tp is determined first by adopting the following measurement conditions together with the method illustrated in Diagram 3.4 for measuring the force F needed to rotate the screws shaft without bringing the nuts to rotate along with the shaft after the screws shaft has started rotating,then multiplying the measured value of F with the arm of force L,the product is Tp.
TP=F·L
Measure Conditions
(1) Measurement is executed under the condition of not attaching with scraper.
(2) The rotating speed during measurement maintains at 100rpm”C
(3) A ccording to JSK 2001 (industrial lubrication oil viscosity classification standards), the lubrication oil used should be in compliance with ISO VG68. |
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