Square up a small block of hard wood (soft woods will get worn out too quickly) about 3" long, 1" wide and 1/2" thick. Knife a line to locate the lengthwise center of the block.
|Line knifed in center of block|
Mark the rake angle of your choice on the side of the block next to the hole, as shown above. One line would have sufficed - not sure why I drew 3 lines. Write the angle on the block for future reference. Then line up one side of the saw file with that angle and tap it in. This will leave three little indentations around the hole's edge that you can use later to repeatably place the file at the proper angle.
|Using a ruler to get the angle right|
When a file in installed and you hold the block level, then the one side of the file will be held at the proper rake angle, in my case, 14°
For the fleam angle, mark and then cut the angle on the right side of the block.
|Angle marked ...|
|... then cut and planed smooth (and the angle penciled on the side)|
|Saw file held at 14° rake when block is level,|
20° fleam when angle on right of block is parallel with saw
|Orientation of jig when filing saw with handle (H) on left|
|Orientation after turning saw around with handle (H) on right|
Also, I've written which file that I used with this jig since the hole is sized for that particular file. I have a few of these jigs - one for each size file that I've used.
BTW, if you want to use a jig like this for filing a rip saw, just leave out the cutting of the arrow-point on one end and make the rake angle appropriate for a rip saw.