Flat root side fit
Below talks about Class 2 Fit. (from the Machinery's Handbook 27)
American National Standard Involute Splines*.—These splines or multiple keys are
similar in form to internal and external involute gears. The general practice is to form the
external splines either by hobbing, rolling, or on a gear shaper, and internal splines either
by broaching or on a gear shaper. The internal spline is held to basic dimensions and the
external spline is varied to control the fit. Involute splines have maximum strength at the
base, can be accurately spaced and are self-centering, thus equalizing the bearing and
stresses, and they can be measured and fitted accurately.
In American National Standard ANSI B92.1-1970 (R 1993), many features of the 1960
standard are retained; plus the addition of three tolerance classes, for a total of four. The
term “involute serration,” formerly applied to involute splines with 45-degree pressure
angle, has been deleted and the standard now includes involute splines with 30-, 37.5-, and
45-degree pressure angles. Tables for these splines have been rearranged accordingly. The
term “serration” will no longer apply to splines covered by this Standard.
The Standard has only one fit class for all side fit splines; the former Class 2 fit. Class 1 fit
has been deleted because of its infrequent use. The major diameter of the flat root side fit
spline has been changed and a tolerance applied to include the range of the 1950 and the
1960 standards. The interchangeability limitations with splines made to previous standards
are given later in the section entitled “Interchangeability.”
There have been no tolerance nor fit changes to the major diameter fit section.
The Standard recognizes the fact that proper assembly between mating splines is dependent
only on the spline being within effective specifications from the tip of the tooth to the
form diameter. Therefore, on side fit splines, the internal spline major diameter now is
shown as a maximum dimension and the external spline minor diameter is shown as a minimum
dimension. The minimum internal major diameter and the maximum external minor
diameter must clear the specified form diameter and thus do not need any additional control.
The spline specification tables now include a greater number of tolerance level selections.
These tolerance classes were added for greater selection to suit end product needs.
The selections differ only in the tolerance as applied to space widthand tooth thickness.
