At its upper end, the insert has a head 33 provided with axial serrations 34 on its outer circumference.

Such relatively soft bodies as are referred to herein, include relatively soft materials such as aluminum and magnesium alloys, dural, wood and plastic materials such as synthetic resins and the like.

The invention also contemplates certain special cases of materials usually considered as being fairly hard, such as steel, provided the insert or any portion thereof designed to cut into the material in question, be of still harder material.

Particularly in the case of aircraft construction, where the fastening is subject to constant vibratory action, assurance must be provided that the insert will pot loosen and fail either by longitudinal displacement or by rotation.

The inserts have been embedded directly in the plastic material, during the moulding or casting thereof, and the inserts have been so shaped that they formed an intimate union with the material of the body, effectively preventing their removal..In many cases, constructions of this type have been satisfactory for their Intended purposes, but difficulty has arisen when the inserts have become damaged by carelessness, accident, or excessively abusive usage.

Moreover, prior to the present invention, it was impossible to replace such a damaged insert with a new insert which would be held within the body with substantially the same firmness as the original one.

Inserts of the prior art have been secured in plastic bodies against longitudinal movement and relative rotation, by moulding the plastic material about their exterior surfaces, but with such constructions, the inserts could not be removed without materially damaging the bodies.

When attempts were made to remove them by completely drilling them out, it was impossible to replace them with substitute inserts, since no construction was available which could be applied to the drilled-out hole to resist both longitudinal and rotational movement.

Also, a number of methods of removing and replacing different types of inserts in different materials are diagrammatically illustrated.

It must be understood, however, that the invention is not limited to the details of construction or to the procedural steps shown and described, since many modifications will readily occur to those skilled in the art from a consideration of this disclosure.

Of course, this body may be of any suitable size and shape, for its intended purpose.

In the embodiment illustrated, the neck IT is of a diameter substantially equal tc the root diameter of the thread 14.

It is important that this neck be of less diameter than the maximum diameter of the thread 14.

The drill selected for this operation should be of a size between the diameter of the neck 17 and a diameter just less than the overall, maximum diameter of the lands of the threads 14.

As shown in Figure 3, the drill extends downwardly below the undersurface of the head 15 and preferably terminates substantially at the threaded section of the shank.

In this condition of the parts, the thread 14 projects outwardly beyond the inner circumference 22 of the head 15 and underlies the portion of the head adjacent thereto.

The thread 14 cuts a groove in the plastic body as the insert is rotated.

It will be evident that the greater the diameter to which the bore 22 is drilled, the less will be the depth of this groove, and it is accordingly desirable from the standpoint of ease in removal that the bore 22 be as large as possible.

On the other hand, the bore 22 must be adequately smaller than the outside diameter of threads 14, for a reason that will immediately appear.

When the body 10 is comparatively soft, the bore 22 may be substantially equal to or just slightly in excess of the diameter of the neck 17.

As the threaded shank 12 is unscrewed, its upper end 26, more particularly the uppermost point on the thread 14, will engage the undersurface of the disconnected head 15, applying axial force thereto and causing the head to be axially removed from its cavity in the body 10, this movement being permitted by the axial serrations on the head 15 and the correspondingly shaped margins of the cavity.

As explained in that application, the insert comprises a cylindrical member 30 having an internal thread 31 and an external thread 32 adapted to mate with the thread 27 in the bore formed in the body 10.

Rosan Stud Removal Tool