I get lots of questions through the blog from readers and now students that have taken my saw sharpening classes. Saw filing questions are increasing, and I thought I’d share one from a student who took my class at Shady Lea Woodworking here in Rhode Island.
The question concerned what to do about one of the most common maladies in saw filing: the dreaded ‘cows and calves’ or ‘big tooth, little tooth’ syndrome as I call it. This is essentially a condition were after filing your saw teeth they exhibit a pattern of one larger tooth with a deep gullet followed by a smaller tooth with a shallower gullet and so on down the tooth line. Here’s a pic from the reader of his affliction…
You can really see it in the right hand half of the picture….those one big, one small, one big, one small teeth are the problem we’re talking about. The reason this is not good is because unequal sized teeth and gullets do unequal work…larger teeth with deeper gullets take bigger bites, and smaller teeth with shallower gullets take smaller bites. This makes for inefficient cutting.
So here’s the remedy….and the advice I gave the student:
Any time you sit down to file a saw and the teeth are out of joint, start by running your mill file down the teeth. This step is called ‘jointing’. Now, instead of filing away half of each flat created by the jointing (as is the common practice) allow yourself only TWO file strokes on each tooth all the way down the toothline. Don’t worry about the flats. Make your strokes consistent in pressure and length. However, if two strokes is removing more than the whole flat on each tooth, it means you should joint it down further before starting.
Now sight down the length of the saw and look at the gullets. Identify the gullets that are shallower than their neighbors (the smaller teeth with less depth). Beginning at the heel, sight the toothline and find the first gullet that stands out as shallower than its two neighbors. File this gullet until it is even in-depth with the neighboring gullets. Now work your way down the toothline with the same approach filing only the gullets that are shallow. When you reach the toe, all of your gullets should now be even. Now you can joint the saw again and begin filing each tooth with the traditional approach of removing half the flat. Make sure you keep the gullets even by accentuating your file stroke towards the larger flat. Once your teeth are all even, you can set and sharpen the saw.
In essence, this approach (which I simply call ‘Evening the Gullets’) makes you focus on the teeth/gullets that need filing and prevents you from filing those that are already at full depth any deeper and thereby robbing the shorter teeth/gullets of the space to be made even.
Make sense? Good. And if you’ve already got a saw with ‘cows and calves’ like the picture above, you don’t have to joint it again to correct it…just start at the point where you file only the shallow gullets. And there you go: Cows and calves defeated! Veal cutlet anyone?
And of course, like all things in saw sharpening, the key is mastering your file stroke and developing muscle memory. Practice, practice, practice!
Enjoy….and keep makin’ filings!