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Table of contents
No headersCalculates and designs involute spline joints. Generator designs an applicable spline width, bending, and pressure loading are also checked. Only shaft teeth are part of the calculation because the stress in the shaft is greater than the hub teeth that have a greater root thickness.
Couplings with involute splines are suitable for transfers of great, cyclical, and shock torsional moments. This type is used both for fixed and for sliding couplings of cylindrical shafts with hubs. The use is similar as with parallel splines.
- Lower pressures than couplings with keys, higher loading capacity of the coupling
- Lower wear of sliding couplings.
- Suitable also for cyclical torsional moments.
- Easy assembly and disassembly of the coupling.
Advantages of the coupling compared with parallel splines:
- Higher number of teeth (lower pressures, higher loading capacity of the coupling, more uniform distribution of forces along the perimeter, option of fine adjustment of the hub on the shaft).
- Lower weakening of the shaft, lower notch coefficient.
- Economical lot production using a hobbing method.
- High accuracy of production similarly as with accurate gears.
Disadvantages of the coupling:
- Higher production costs than couplings with keys.
- Higher notch coefficient than couplings with keys.
- Difficult execution of alignment and perpendicularity of the coupling.
- Nonparallelism of sides of the teeth causes additional radial forces in the coupling. These forces then try to open the hub.
The splined profile is shaped as involute toothing in the cross section, with basic angles of the profile 30°, 37.5° or 45°. It is centered to the outer diameter or sides of the teeth. Centering to the diameter is more accurate, centering to sides is more economical and is used much more frequently in practice The groove bottom can be flat or rounded.
How to design involute splines
Insert involute spline connection
Edit involute spline connection
Insert individual connection component - shaft groove
Additional insertion of connection components
Involute Spline Generator - Design tab
Sets parameters for calculation of an involute spline.
Access: |   |
Specifies basic spline properties. | |
Splines Type | Specifies the spline type you select in the dialog box displayed when you click the arrow next to the Splines Type edit field. Click the spline type, and it is entered into the edit field. |
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Spline | Spline dimensions are updated based on the selected spline. |
Length | Specifies the spline length. |
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| Displays the Tolerances dialog box where you can enter tolerances. |
To display the Results area on the right side of the Calculation and Design tabs, double-click the double line on the right or click the chevron.
The area displays the calculated values and the spline strength check. Values are calculated when you click Calculate.
The units of the results values can be changed. Double-click the specified value you want to change.
Displays the reports about calculation.To open the Summary of Messages area at the bottom of the Calculation and Design tabs, double-click the double line at the bottom of tabs or click the chevron at the bottom of the tabs.
A graphic preview of the selected geometry is displayed. You can use grips to specify spline length, for example.
Involute Splines Generator - Calculation tab
This tab extends the Design tab. Calculates generator data based on selections in the Design tab.
Access: | and click the Calculation tab. |
Method | |
ANSI Method | Performs calculation according to the ANSI standards. |
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| Note: This method is available only if you select ANSI spline in the Design tab. |
Common Method | Performs calculation according to the basic formula when pressure equals force on plane. |
Metric Method | Performs calculation based on CSN 014950 standard. |
Type | |
Check Calculation | Performs a strength check for the specified load, dimensions, and joint properties. |
Length Design | Designs the optimum active spline length for the specified load, spline diameter, and joint properties. |
Loading is entered through power, speed, or torque, depending on the method selected. | |
Power, Torque | Calculates the speed according to the power and torque. |
Torque, Speed | Calculates the power according to the torque and speed. |
Power, Speed | Calculates the torque according to the power and speed. |
Spline | Choose a dimension of the spline. |
Hollow Shaft Inner Diameter | If you use a hollow shaft in the coupling, enter the inner diameter of the shaft here. This parameter effects the size of loading of the shaft in torsion and considerably affects determination of the minimum permitted diameter of the shaft. |
Hub Outside Diameter | Choose the outside diameter of the hub. |
Spline Length | Choose a length of spline within the standard specified range so that it is larger than the minimum length. |
In the material edit field, specify your own material values or select a material from Material Database. If a material is selected from Material Database, its value is inserted into the following edit field, and the edit field is locked. To unlock the field, clear the check box. | |
Allowable Pressure | Enter the allowable pressure of the spline material with the least quality in the Joint Properties group. The spline is checked for pressure during the strength check. |
Allowable Shear Stress | Enter the allowable pressure of the spline material with the least quality in the Joint Properties group. This value is used in designing the minimum shaft diameter. |
Allowable Compressive Stress | Available only if you select the ANSI spline in the Design tab. |
In the material edit field, specify your own material values or select a material from Material Database. If a material is selected from Material Database, its value is inserted into the following edit field, and the edit field is locked. To unlock the field, clear the check box. | |
Allowable Pressure | Enter the allowable pressure of the spline material with the least quality in the Joint Properties group. The spline is checked for pressure during the strength check. |
Allowable Shear Stress | Enter the allowable pressure of the spline material with the least quality in the Joint Properties group. This value is used in designing the minimum shaft diameter. |
Allowable Compressive Stress | Available only if you select the ANSI spline in the Design tab. |
Allowable Tensile Stress | Available only if you select the ANSI spline in the Design tab. |
To display the Results area on the right side of the Calculation and Design tabs, double-click the double line on the right or click the chevron.
The area displays the calculated values and the key strength check. Values are calculated when you click Calculate.
The units of the results values can be changed. Double-click the specified value you want to change.
Displays the reports about calculations. To open the Summary of Messages area at the bottom of the Calculation and Design tabs, double-click the double line at the bottom of tabs or click the chevron.
Tolerances (for ANSI Metric standard)
Specifies the tolerance class and fit class.
Access: | . In the Involute Spline Connection Generator, click  next to the Length edit field. |
OK | Confirms the selection and closes the dialog box. |
Cancel | Closes the dialog box. |
Tolerance class
Select the class of the tolerances.
This standard includes four classes of tolerances on space width and tooth thickness to provide a range of tolerances to meet a design need. The classes are variations of the former single tolerance which is now Class 5 and are based on the formulas shown in the footnote of Table 4. All tolerance classes have the same minimum effective space width and maximum effective tooth thickness limits so that a mix of classes between mating parts is possible.
For other tolerance classes:
Class 4 = 0.71 x Tabulated value
Class 5 = As tabulated in table
Class 6 = 1.40 x Tabulated value
Class 7 = 2.00 x Tabulated value
Tolerance class
Select the class of fit.
The Standard provides the same internal minimum effective space width and external maximum effective tooth thickness for all tolerance classes. It is possible to interchange an assembly between mating splines regardless of the tolerance class of the individual members, and permits a tolerance class "mix" of mating members. This arrangement is often an advantage when one member is considerably less difficult to produce than its mate, and the "average" tolerance applied to the two units is such that it satisfies the design need. For example, by specifying Class 5 tolerance for one member and Class 7 for its mate, an assembly tolerance in the Class 6 range is provided.
Fit Classes: Four classes of side fit splines are provided: spline fit class H/ h having a minimum effective clearance, cv = es = 0; classes H/ f, H/ e, and H/ d having tooth thickness modifications, es , of f, e, and d, respectively, to provide progressively greater effective clearance cv. The tooth thickness modifications h, f, e, and d are fundamental deviations selected from ISO R286, "ISO System of Limits and Fits." They are applied to the external spline by shifting the tooth thickness total tolerance below the basic tooth thickness by the amount of the tooth thickness modification to provide a prescribed minimum effective clearance cv.
Tolerances (for ANSI standard)
Specifies the tolerance class and spline type.
Access: | . In the Involute Spline Connection Generator, click next to the Length edit field. |
OK | Confirms the selection and closes the dialog box. |
Cancel | Closes the dialog box. |
Spline Type | |
Straight-toothed Spline | Toothed splines for small angle inaccuracy (maximum 1 degree). |
Crowned Spline - flexible | External splines with crowned teeth for misalignment up to five degrees. |
Tolerance class
Select the class of the tolerances.
This standard includes four classes of tolerances on space width and tooth thickness. This provides a range of tolerances for selection to meet a design need. The classes are variations of the former single tolerance which is now Class 5 and are based on the formulas shown in the footnote of Table 4. All tolerance classes have the same minimum effective space width and maximum effective tooth thickness limits so that a mix of classes between mating parts is possible.
For other tolerance classes:
Class 4 = 0.71 x Tabulated value
Class 5 = As tabulated in table
Class 6 = 1.40 x Tabulated value
Class 7 = 2.00 x Tabulated value
Types and Classes of Involute Spline Fits
National Standard for involute splines, the side fit, and the major diameter fit.
Dimensional data for flat root side fit, flat root major diameter fit, and fillet root side fit splines are tabulated in this standard for 30-degree pressure angle splines; but for only the fillet root side fit for 37.5- and 45-degree pressure angle splines.
Side Fit: In the side fit, the mating members contact only on the sides of the teeth; major and minor diameters are clearance dimensions. The tooth sides act as drivers and centralize the mating splines.
Major Diameter Fit: Mating parts for this fit contact at the major diameter for centralizing. The sides of the teeth act as drivers. The minor diameters are clearance dimensions. The major diameter fit provides a minimum effective clearance that allows for contact and location at the major diameter with a minimum amount of location or centralizing effect by the sides of the teeth. The major diameter fit has only one space width and tooth thickness tolerance which is the same as side fit Class 5.
A fillet root may be specified for an external spline, even though it is otherwise designed to the flat root side fit or major diameter fit standard. An internal spline with a fillet root can be used only for the side fit.
Access: | . In the Involute Spline Connection Generator, click next to the Length edit field. |
OK | Confirm the selection and close the dialog box. |
Cancel | Closes the dialog box. |
Centering to Groove Sides |
Center to sides of the groove. Set the tolerance grades for shaft and groove. |
Centering to Outside |
Center to outside diameter. Set the tolerance values. |
Specifies the tolerance class and fit class.
Access: | . In the Involute Spline Connection Generator, click next to the Length edit field. |
OK | Confirm the selection and close the dialog box. |
Cancel | Closes the dialog box. |
Centering to Groove Sides | |
Set the tolerance grades for shaft and groove. | |
Test Dimensions Settings | |
User | Check the box to enter the user values. If the box is not checked, the values are calculated according to the appropriate standard. |
Pin Diameter, Shaft | Pin diameter on the shaft. |
Finishing of Flanks | |
Select the way the grooves on the shaft and hub are created. | |
Specifies the tolerance class and fit class.
Access: | . In the Involute Spline Connection Generator, click next to the Length edit field. |
OK | Confirm the selection and close the dialog box. |
Cancel | Closes the dialog box. |
Tolerance class
Select the class of the tolerances.
This standard includes four classes of tolerances on space width and tooth thickness. This provides a range of tolerances for selection to meet a design need. The classes are variations of the former single tolerance which is now Class 5 and are based on the formulas shown in the footnote of Table 4. All tolerance classes have the same minimum effective space width and maximum effective tooth thickness limits so that a mix of classes between mating parts is possible.
For other tolerance classes:
Class 4 = 0.71 x Tabulated value
Class 5 = As tabulated in table
Class 6 = 1.40 x Tabulated value
Class 7 = 2.00 x Tabulated value
Fit class
Select the class of fit.
Specifies the influence of production and operating parameters on the connection acceptability.
Access: | On the Design tab, Power Transmission panel, click Key, Involute Splines, or Parallel Splines, and on the Calculation tab click Loading Conditions. |
Joint Type | |
Fixed | Splines are firmly joined by pressing or fixed by rings, avoiding axial movement. |
Flexible | Splines are flexibly joined to allow axial movement. |
Crowned | Uses external splines with crowned teeth for misalignment up to 5 degrees. |
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Ka - Application factor
This coefficient reflects the effect of the character and the type of loading on decrease of the loading capacity or the coupling. It is determined according to empirical values given in the following table:
Drive | Type of loading | |||
Continuous | Light shocks | Cyclical shocks | Heavy shocks | |
Uniform | 1.0 | 1.2 | 1.5 | 1.8 |
Light shocks | 1.2 | 1.3 | 1.8 | 2.1 |
Medium shocks | 2.0 | 2.2 | 2.4 | 2.8 |
Fatigue-life factor
This coefficient reflects effects of the operational character and appropriate service life of the coupling (measured in number of torque cycles) on increase of the loading capacity of the coupling. It is determined according to empirical values given in the following table:
No. of Torque Cycles | Fatigue-life factor, Kf | |
Unidirectional | Fully bi-directional | |
10000 | 1.0 | 1.0 |
100000 | 0.5 | 0.4 |
1000000 | 0.4 | 0.3 |
10000000 | 0.3 | 0.2 |
Wear-life factor
This coefficient reflects effects of wear of contact surfaces during the appropriate service life of the coupling (measured in number of revolutions) on increase of the loading capacity the coupling. It is determined according to empirical values given in the following table:
Load Distribution factor
In couplings with two keys, the loading is not distributed exactly uniformly onto the two keys due to production and assembly inaccuracies. The actual load bearing surface of the coupling is lower than the load bearing surface determined theoretically. The ratio between the theoretical and actual load bearing surface of the coupling is defined by the coefficient of distribution of the loading. With regards to the accuracy of bearing, the size of the coefficient is given in a range from 0.6 to 0.8.
Tip: For common accuracy of production and installation, a coefficient of 0.75 is taken into account .
Factor of Tooth Side Contact
The factor indicates the load is not spread evenly on all the spline teeth because of production and assembly inaccuracy. At a common and higher mounting accuracy, it is assumed that half of the teeth carry the load (Ks = 0.5). For splines with higher production inaccuracy, the load is only carried by one third of the teeth (Ks = 0.3).
Loading Conditions - Metric method
Specifies the influence of production and operating parameters to the connection acceptability.
Access: | . In the Involute Spline Connection Generator, on the Calculation tab, click Loading Conditions. |
Joint type | |
Fixed | Joins splines firmly by pressing or fixed by rings avoiding axial movement. |
Working Conditions | |
Specifies the type of working conditions. | |
Tooth Side | |
Specifies the type of tooth sides. | |
Recommended values of allowable pressures on tooth sides:
Type of loading | Working conditions | Hardened Tooth Side | Non-Hardened Tooth Side | |
flexible | under load | adverse | - | 0.3 - 1 |
medium | - | 0.5 - 1 | ||
advantageous | - | 1 - 2 | ||
no load | adverse | 1.5 - 2 | 2 - 3.5 | |
medium | 2 - 3 | 3 - 6 | ||
advantageous | 2.5 - 4 | 4 - 7 | ||
fixed | adverse | 3.5 - 5 | 4 - 7 | |
medium | 6 - 10 | 10 - 14 | ||
advantageous | 8 - 12 | 12 - 20 | ||
Factor of Tooth Side Contact
The factor indicates the load is not spread evenly on all the spline teeth because of production and assembly inaccuracy. At a common and higher mounting accuracy, it is supposed that one half of teeth carry the load (Ks = 0.5), for splining with higher production inaccuracy the load is only carried by one third of teeth (Ks = 0.3).