Re: Rip saw sharpening questions *PICS*
L. Hanson
>Here's something I put on my web site - I know there are others that have the some info, and I would still recommend checking them out - at least vintagesaws.com library, as well as disstonianinstitute.com. This is just more info, is all. Hopefully it can be of some help.
Shaping the teeth:
If the teeth aren't very uniform, the first step is to shape the teeth so that they are. When shaping, I usually work from one side only. Trying to skip every other tooth is difficult at best, and unnecessary at this point - as I'll finish sharpening them later by doing every other tooth. One note if you are shaping from one side only - you need to make sure you are holding the file perpendicular to the blade, and not angling the file up or down - if so, the final sharpening process will be much more difficult.
First, I 'joint' the saw - that means filing the top of the saw so each of the teeth are just slightly flattened. I just use a file with a square scrap of wood to help hold it perpendicular to the saw, but name brand jointers are available as well. Here you can see the reflection of the freshly flattened parts of the teeth by their reflection:
File just enough so that you can see a flat spot forming on all of the teeth - if there are one or two that aren't, it's not a big deal - subsequent sharpenings will bring them out. But only a couple...
You can see (maybe - kind of blurry) some of the flat spots on the top of the teeth in this photo after I've jointed them:
If the result of jointing shows evenly sized 'flat spots' on top of the teeth, you can skip the shaping section and go directly to sharpening. However, you can see in this instance that some of those flat stops are larger than others - and some are hardly there at all. We'll need to fix this while the teeth are being sharpened because ideally, they would all be the same. This point to a problem with the size of the existing teeth - that some are more deeply filed than others, and consequently that the points of the teeth are not all the same height - so the saw will not work as well.
What brought this about? Not paying enough attention to details. Many sharpeners simply count the number of strokes they make with the file, but sometime they might be putting more pressure in one direction than in the other, and this is the result... Not to worry - it's easily taken care of. In either case below, when you are sharpening, you are sharpening to the point where the flat spot you created in this step *just * disappears... You will notice, as you go, how much pressure it takes to do just that. Plus, guided by the flats on top of the saw, you can apply a slight amount of pressure to the side that has more flat than it should.
This is why I do shaping from one side, as I mentioned above, as doing every other one can be a little bit tricky for your first pass. If you do every other tooth from each side - just file more conservatively on the first side you do, then return to it to finish the job. That way you are sure you aren't overdoing it on one side and getting yourself into trouble.
Sharpening the teeth
For sharpening rip saws - file across every other tooth from one side, then flip the saw and run the file from the other direction on the remaining teeth with at least one end of the file jammed into a block of wood like shown below. Filing from each side is done so the filing is consistent from each direction, and any inconsistencies that are created by your technique are repeated in an opposite and equal manner. The angle should be the same one chosen previously (the lower is the less aggressive pitch):
The top one is the more aggressive pattern, which can be more difficult to use if you're not as experienced with hand saws as you'd like to be. If starting cuts is an issue with you, you might consider the lower diagram (or something between the two) which relieves the angle of attack slightly to make for a less aggressive cut. It'll be slower, but easier to use. Disston started using the lower profile at some point after the turn of the century for some of their saws, so there's no need to feel like you're cheating if you do decide to use the less aggressive cut. I know users who sharpen their dovetail rip saws up to a full 15 degrees to make them easier starting. I would suggest you experiment with your own to find out where you are most satisfied.
It often helps to use something to darken the teeth so you can see which teeth you've filed and which you haven't. You can use chalk, layout dye, or "Sight Black", which an anti-reflective aerosol spray used by gun-owners for reducing glare when sighting through their scopes. It wipes off easily, leaving nothing behind. Another great method is to use the soot from a burning candle or alcohol lamp.
As shown in the above diagram, file the teeth at 90 degrees to the blade, using the same angle used in shaping the teeth above. Here's the real-world shot:
Usually, only a light stroke or two of the file is needed, just enough to remove the "flat" part left behind in the step above. The flat will help you as a reference, filing the very last of it away should leave all of the points of the teeth in the same plane along the length of the saw. Use the set of the saw to help guide you - for example, keep the tooth that is bent away from you to the right side of the file. When you flip the saw, the orientation will remain the same - and if you darkened the teeth as suggested above, it should be easy to see where you've filed and where you haven't.
Setting the teeth
Now is a good time to "set" the teeth. "Setting" the teeth simply refers to bending every other tooth over slightly one way (the remaining are bent the same amount the other way) to increase the kerf size cut by the blade. You can see the end effect in the rip and crosscut profiles diagrammed above. The reason for this is to keep the blade from binding against the wood its cutting. Softwoods need more set, as they "spring back" more. Wet woods need the most set. Hardwoods need less, and for cabinet grade hardwoods, it's best to try and get away with as little kerf as possible. It's been my experience that you need at least some.
Setting the saw is done with a tool called, surprisingly, a saw set. Stanleys are among the most common with the 42x being my preferred - but others can be just as serviceable. For teeth finer than 14 PPI, it might be necessary to file down the hammer of one of these so it fits properly over the saw tooth. The ultimate goal is to end up with a set where about 1/2 of the tooth is bent over. Subsequent sharpenings reduce the amount of set simply by filing it away as you file down the tooth, therefore requiring you re-set the teeth at least every third sharpening, and maybe more often with finer teeth.
Using a saw set - notice the mark I've made on every other tooth with a marker:
Start by setting every other tooth on one side, then flip the saw around and set the remaining teeth the other direction. Like I said, I don't always set the teeth during every sharpening, as sometimes I don't file enough off to significantly affect the set. But when I do, I will always set it *just* a little more than I think is necessary. You'll see why in the tuning section.
A word of warning - if you set a tooth one way, then decide you need to set it the other way, you could break the tooth off. It is generally good practice to avoid doing it, so heed the following advice. One problem I always seem to have when setting fine teeth is that I lose my place while setting every other tooth. To overcome this, I often take a marker such as a Sharpie and mark every other tooth for reference, as I mentioned above. This helps me avoid problems like mentioned above where you accidentally set the teeth the wrong way. If you do - don't fret, it's not the end of the world. Subsequent filings will essentially remove the set, and at some point in the future you can start over. Till then, it won't make a huge difference in how the saw performs so long as you are consistent in the set from side to side. But do try to avoid it.
Once I've set the teeth, sometimes I will go over the saws once again with a file to sharpen them one last time - very lightly - to account for the new set. Then it's ready for a final tuning...
Final Tune Up:
Wax the blade of the saw using a paste wax such as Johnson's Paste Wax. Avoid waxes that contain silicone, as this can contaminate some finishes... simple paste wax is best and it is amazing how much it can improve performance.
Lightly stone both sides of the teeth to even them out. Errant teeth both reduce efficiency and leave the surface rougher than need be. Stoning the sides evens the set of the individual teeth:
Once you get used to sharpening and tuning your own saws, you will develop a feel for what types you need, and how to tune each for it's intended purpose. I've tried laying out a few simple guidelines here, but so much of it comes from jsut doing it - well, you'll see! Once you've made those first cuts with a sharp saw..
Leif
www.norsewoodsmith.com
