Saw chains with chipper or chisel cutting links are sharpened by filing with a round file. In order to get best cutting properties, it is required that the file is held at a certain angle to the transverse direction of the saw chain and the guide bar. This angle varies between different chain types and different tree species, but is commonly between 25 and 40 degrees.

To help the operator hold the file at the desired angle, there are several filing guides available, such as described in the patents US 4,177,697, US 4,404,871 and 4,228,702 but must of those are too complicated or too fragile to be used in the woods, and they are not readily adjustable to other angles.

There are also known designs of file handles which include means to indicate a proper angle of filing. Since saw chains are made from hard and often chrome plated material, a chain saw file wears rapidly, and usually the handle is not discarded with the file but used to hold the next chain saw file. It is thus made with tightenable jaws and not adjustable to different angles.

According to the invention the chain saw file is held with a unitary file handle such as used for larger mill files with tapering rectangular tangs by means of a plastic collet which also indicates the proper filing angle.

Description

The invention is described with reference to figure 1 showing the collet from above, figure 2 showing the collet from the side, and figure 3 showing the collet from the rear.

CONFIRMATION

The collet has a rear tang part (10) shaped like the tang of a mill file, of equal thickness seen from the side and tapering seem from above, and a front part with two wings

(11,12) . Through the length of the collet is a hole (13) with a cross-section corresponding to that of a chain saw file (14) , which can be pushed into the hole. When the collet is then pushed into a file handle (15) designed to fit mill files, the collet tang (10) is compressed to hold the chain saw file (14) firmly.

The front end has a thickened portion (16) between the wings

(11,12) to hold the file properly, forming a step (18) to the rear to aid in prying the collet loose from the handle

(15) when the file is worn out. The collet tang (10) may be made with one or more lengthwise slits to make it more compressible when pushed into the file handle (15) .

The front edges of the wings (11,12) forms such an angle with the hole (13) that the intended filing angle is achieved when the front edge of a wing is parallel to the chain being filed. Each wing can be made with a different angle, and in such case the wings should carry identification marks (17) telling either the angle or the type of chain requiring that angle.

The collet is preferably made from a flexible plastic material to get the desired wedging action when pushed into the handle (15) , but it could also be made from thin spring steel, pressed into corresponding shape. The collet is so small that it is possible to carry several collets along with the files, and exchanging the collet to choose another angle of filing.