3.2.1 Mandrel. The portion of the mandrel in contact with the rolls shall have a taper of
0.030 to 0.032 inch per inch of mandrel length. To prevent the expander body from remaining in
the tube when the mandrel is withdrawn, the mandrel shall have a threaded end with nut except
that mandrels for 3/8 inch and smaller size expanders may use other means for mandrel retention.
The mandrels for 1/2 inch and larger size tube expanders shall be provided with either a l/2-inch
square shank or a No. 1 Morse taper shank as specified (see 62). The mandrels for less than 3/8
inch size expanders shall be provided with a 1/4-inch (0.240 to 0245 inch) square machined on
the last 1/2 inch of a 5/16 inch round shank for a Jacobs chuck The tapered length of the mandrel
shall be ground to a surface finish of 32 RMS or smoother. Grinding shall remove all decarbonized
metal and distortion from the tapered length of the mandrel.
3.2.2 Body. The body shall be slotted to contain three taper rolls, set 120 degrees apart at
a lead angle of 1/4 to 2 degrees, and shall have a threaded section on which shall be mounted a
collar, collar sleeve bearing, and sleeve, adjustable in position on the body so as to regulate the
depth of penetration of the rolls into the tube, and secured by a lock nut or other positive means.
The length of the body and threaded section on the body shall be tailored to the location and
thickness of the tube sheet for which the expander is intended to be used relative to the end of
the tube (see 6.2).
3.2.3 Collar. The collar shall be threaded internally to suit the threads on the body. An
antifriction type thrust bearing shall be mounted on the collar with a sleeve mounted on or made
integral with the bearing.
3.2.4 Collar sleeve. The collar sleeve for single tube sheets or outer tube sheets on double
tube sheet designs shall cover the small ends of the tapered rolls with the collar and locknut
adjusted as close to the rolls as possible. The collar sleeve of all expanders over the l/4-inch
tubing size shall be recessed 1/16-inch (plus 1/64 inch minus O) to fit over the end of the tube. The
diameter of the collar sleeve recess shall be not less than 1/32 inch larger than the outside
diameter of the tubes for which the expander is intended.
3.2.5 Rolls. The rolls shall have a taper which shall measure 0.015 to 0.016 inch per inch of
roll length so as to produce parallel expansion of the tube. The effective length of the rolls shall
be such that, together with position adjustment of the collar, the expander will be suitable for
rolling the tubes to within 1/8 inch of the inner face of the tube sheet (within 1/8 inch of each
face on an inner tube sheet), the thickness of which is specified, or to the maximum depth
specified (see 6.2). The rolls shall be ground after heat treatment to remove all decarbonized steel
and distortion. Surface finish shall be 32 RMS or smoother. The rolls shall be arranged so that
they will not fall out of the body unless the expander is disassembled. When the mandrel is
inserted to within 1/4 inch of the shoulder, the rolls shall not be body-bound. Rolls furnished with
expanders designed to seat tubes in inner tube sheets or for use in retractive rolling shall be
rounded at each end to prevent scoring the tube at the beginning and end of the relied section.
Rolls furnished with expanders designed to seat tubes in outer tube sheets shall be rounded at the