Guide for filing saw chain

#This invention relates to a guide for a file to be used in sharpening a chain saw chain.

#Chain saws are widely used in logging. They comprise a housing carrying a small gasoline motor with an output shaft carrying a drive sprocket. A chain extends around a chain bar which supports and guides the chain. The chain also engages and is driven by the drive sprocket. The chain has drive teeth to engage the drive sprocket and cutter teeth, which cut the wood. These cutter teeth must be kept sharp and properly maintained. The chain moves at high speed and although chain saws have proved to be a huge advantage in logging they can be very dangerous tools to use, especially when not properly maintained, and not properly sharpened.

#An improperly sharpened chain can increase the risk of the chain saw kicking back, that is being forced out of the wood, towards the operator. This kicking back is a major hazard in operating a chain saw.

#Aspects of the invention are illustrated, merely by way of example, in the accompanying drawings in which:

#FIG. 1 is a perspective view of a guide according to the present invention;

#FIG. 2 is on the line 2--2 in FIG. 1; and

#The drawings show a sharpening guide for a file to be used in sharpening a saw chain. The guide comprises a substantially semi-cylindrical body 2 that is a close fit on a round file of predetermined size. A file 4 is shown in position in FIG. 3.

#There is a first support 6 at one end of the body 2 to support and guide the file 4 during use and, in particular, to ensure that the file 4 remains within the guide. In the preferred embodiment illustrated there is a second support 8 at the end of (he body 2 remote from the first support 6. The dimensions of the first and second supports 6 and 8 and of the semi-cylindrical body 2 is such that the file 4 and body 2 can reciprocate back and forth, during the filing motion, but the file 4 also can rotate readily within body 2 so that differing parts of the file can be used. However, the fit is reasonably close as, of course, the guide has to function to maintain a stable position for the file during sharpening.

#Preferably the guide is of heat hardened steel although any appropriate material that is not affected by filing can be used.