Fitted bolts to DIN 609, DIN 610, DIN 7968 and to drawing

A fitted bolt has a fitted shank between head and thread whose diameter is manufactured to a close tolerance, for example k6, js6 or h8. This shank sits in a hole with an equally close tolerance and transmits shear forces through a form fit; the bolt centres the components relative to each other and at the same time holds the joint together through preload. Fitted bolts are standardised as DIN 609 and DIN 610 with a hexagon head and long or short thread, as DIN 7968 for steel structures and as ISO 7379 with a cylindrical head and hexagon socket. The fitted diameter is larger than the thread diameter, for example M20 with a 21 mm fitted shank.

Where fitted bolts are used

Shaft flange couplings, gearbox housings, flywheels, bogies and wheelsets of rail vehicles, crane and steel structure connections subject to shear, presses and rolling mills: wherever components under alternating load must not slip relative to each other.

What matters in production

The fitted shank is turned after quenching and tempering and, depending on tolerance and surface finish, ground; in-house grinding is typically up to 40 mm diameter, larger diameters are ground by partners. Roundness, cylindricity and the transition to the thread with undercut are measured and recorded on request. The thread is rolled, the head forged or turned. Property classes 8.8 to 12.9 are standard, stainless versions and special materials are possible; marking and 3.1 or 3.2 inspection certificate as for all parts made to drawing.

What you should specify

Drawing or standard, fitted diameter with tolerance and surface finish, length of the fitted shank, thread and thread length, property class or material, coating, whether a dimensional report is required, quantity.