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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.
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.
Involute Splines Generator - Calculation tab
This tab extends the Design tab. Calculates generator data based on selections 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.
Tolerances (for ANSI Metric standard)
Specifies the tolerance class and fit 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.
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
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.
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. |
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.
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.
Specifies the tolerance class and fit class.
Specifies the tolerance class and fit 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.
Class 4 = 0.71 x Tabulated value
Class 5 = As tabulated in table
Class 6 = 1.40 x Tabulated value
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. |
|
| |
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:
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).