One of the main aspects of sharpening saws is setting the teeth but I thought this article may be of help to highlight an important aspect rarely shared with woodworkers when it comes to setting the teeth on some old saws.
Much depends on the maker and age but in general many, but not all, old saws can be sharpened, however all the effort in doing this can be undone with over zealous setting of the teeth which can cause a tooth to snap off. Hopefully this article will highlight the difference between setting new and old saws.
I have always used an Eclipse saw set, these are comfortable and give good control over how much set is added with a clear view of what is going on. The settings on it can be a little deceiving as the numbers on the dial in my opinion refer to ‘points per inch’ rather than ‘teeth per inch’ but it’s also important to add that this should not be taken as gospel and each saw should be set according to how it sharpened. Remember all a set does is to create a clearance so the saw plate can run smoothly and over setting can cause wayward cuts and excess material removal which is effectively increasing the workload when cutting timber.
When sharpening an old saw it gives some indication as to how hard the steel is and this should be used to determine how far you try to set that particular saw. Occasionally you may hit a harder spots that requires more strokes of the file to achieve the same depth and I generally mark these with a sharpie so that I am aware when I come back to that tooth later when setting it, take more care when it comes to easing on the pressure with your saw set.
Pressure used when setting is very important and one shouldn’t be trying to crush the steel saw plate with the saw set as this results in deforming the tooth whilst also causing metal fatigue. The pressure should be eased on and any creaking sounds heard is generally a sign of stress from the tooth, so make sure you haven’t got ‘guns and roses’ blasting out in your workshop whilst doing this.
On antique saws you do have to be more aware of what I am describing but often with larger teeth i’ll use the desired setting of the setter but will observe the tooth only needs to create clearance and I won’t crank the tooth right over and will continue at that same rate throughout the setting process.
When to set the saw? I would say when it needs it, there may have enough set to last a couple of sharpening’s, test it after sharpening and check the saw plate doesn’t bind. If i’m sharpening a poorly sharpened saw and it usually requires a lot of jointing and practically a new tooth has to be re-formed, I usually set it before my final run over with the file.
What if you snap a tooth? This is never desirable but it’s not the end of the world, a saw will usually still cut effectively and if you ignore the broken tooth long enough eventually the tooth will be re-formed over time with more sharpening. However if you take on board what I have shared this will become something you can avoid in the future.
Although some vintage and antique saws do require extra care when setting them, it does improve your approach and certainly results in owning a saw that stays sharper for a longer period of time, resulting in less sharpening and the saw retaining its set longer.
That’s what I mean by ‘a perfect saw is hard on the file but still has the ability to set’ and no modern saw ever comes close to a mature vintage one in this case. New saws are generally softer on the file and will set quite easily but depending on the maker they can be less effective when tackling hardwoods, especially when it comes to keeping them sharp. Softer saw plates will often lose their set quicker and often require a hammer set as a result, but losing the set causing friction and binding. This ultimately leads to more effort needed when sawing and usually leads saw plate kinking which then adds to the problem of binding.
Crystallisation of old saw plate results in not being able to set them, the teeth will snap regularly regardless of the set used, when a saw has lost its spring there is very little that can be done with it. That’s why it is preferable to buy saws that have been sharpened and set. Notably the only way to find out is to go through the process of sharpening it and why we sharpen all our old saws here before they are listed for sale.
If you find saw teeth are snapping regularly when setting it’s likely over setting or excessive force is a contributing factor. Luckily most users only have a few saws to sharpen and get time to learn the characteristics and properties those saws possess.
I hope this helps.