Flareless-tube connectors are available in many of the same shapes and threaded combinations as flared-tube connectors (fig. 3-40). The fitting has a counterbore shoulder for the end of the tubing to rest against. The angle of the counterbore causes the cutting edge of the sleeve or ferrule to cut into the outside surface of the tube when the two are assembled.

The nut presses on the bevel of the sleeve and causes it to clamp tightly to the tube. Resistance to vibration is concentrated at this point, rather than at the sleeve cut. When fully tightened, the sleeve or ferrule is bowed

Figure 3-39.- Flared-tube connector.

Figure 3-40.- Flared-tube fittings.

Figure 3-41.- Correct and incorrect methods of installing flared fittings.

NOTE
When tube-type fittings are being tightened, observe the following:

Tighten only until snug. NEVER overtighten. More damage has been done to tube fittings by overtightening than from any other cause.

If a fitting starts to leak and appears loose, retighten only until leak stops.

Where necessary, use two wrenches on fittings to avoid twisting the lines.

Figure 3-42.- Flareless-tube connector.

slightly at the midsection and acts as a spring. This action of the sleeve or ferrule maintains a constant tension between the body and the nut, thereby preventing the nut from loosening.