SPIRO

BENEFITS

• Simple, press-in installation.
• High torque resistance.
• Self-aligning – easy to install.
• Low bursting stresses allows for the use of bosses with thinner walls, while reducing the risk of surface depressions in the plastic.

DESIGN GUIDE

PREPARING THE HOLE

The boreholes for Spiro inserts should always be molded in order to avoid the stresses caused by a drill. The conical shape of a molded hole should not exceed 1°, and the recommended hole diameter is as measured at the level of the hole reached by the end of the insert. The upper part of the hole must not be rounded or chamfered, and be careful to avoid flaring. Hole diameter tolerance: -0.00 + 0.10 mm.

INSTALLATION

The insert is to be installed using a squeeze-action press and NEVER a mallet or similar tool. The insert must be free to rotate in the direction of the knurl during installation. This is best achieved by using a punch tool with either a polished face or a thrust bearing. The insert must be kept axially square during installation, as any tilting will induce lateral loads on the boss wall. The recommended hole size must not be increased beyond the upper tolerance limit, as oversized holes reduce or eliminate the self-alignment effect, which can generate lateral loads and risks bursting the boss.

WALL THICKNESS

In the table, we provide a general guide for determining minimum wall thickness, which can vary based on the type of plastic used. It is possible to use thinner walls if necessary, but we highly recommend contacting PSM CELADA Fasteners for preliminary tests.