No this is not when you take the hammer away from a child because they are making noise by pounding on a hand saw but the purposeful hammering of a saw blade in order to straighten it out.
Hammering was done on new (19th century new) saws once they were made and prepared for sharpening. Hammering was done to ‘tension’ the saw blades during the manufacturing process and work hardens the blade but allows it to remain flexible. And of course hammering is done to old saws that are bent to straighten out a bent or kinked blade. Badly bent or kinked blades that have cracked or fractured the steel of course the hammering will not repair that condition (I am not sure it is possible to repair).
Old blades should be cleaned of rust and brought to as ‘bright’ a condition as possible in order to have a reflective and smooth surface on the saw. Bright tools tend to resist rust. Once it is cleaned, it is time to examine the blade, which I do by sighting down the back of the blade. This also applies to backed saws, sight down the back to see if there are any kinks, bends, bows, cups or curves.
Some hammer saws on a metal anvil, and small saw anvils do exist, I however choose to use a wooden anvil with a slightly different technique. I do have a metal plate that I use occasionally but for the most part it is on top of my chopping stump, a large squared timber cut off at about 34 inches tall, which I use for a variety of uses.
I always straighten out the back of the saw first, as this will usually straighten out the entire blade, depending on the bends and kinks. I hold the saw with the blade straight up and down (the handle) with the back of the saw roughly parallel with the earth. Thus by sighting down the back you should be able to see any problems with the blade. Note where the bends are and place the blade down on the ‘anvil’ with the convex side of the blade up. In other words the bump or kink is bulging up from the anvil.
Planishing hammers with a slightly rounded face is the best, I use a small tinners hammer with a slight belly to its face. It should be a round face to prevent denting, I however use a square faced hammer that I like and it has a slightly convex face (belly). I am comfortable using these smaller hammers and have straightened dozens and dozens of hand saws. I can never resist an old saw for $2.00, and rarely pay more than $10.00. I am careful in my hammering not to go too fast and that my blows are deliberate and controlled so as not to dent the saw while attempting to remove dents.
A few ‘well placed’ blows with the hammer on the bulge, then I check the back of the saw again by picking it up holding it the same and sighting down the back again to check the progress. I do this after every 3 to 6 strikes with the hammer. Later I will check the saw after each blow when things are getting straight. Now what is a ‘well placed’ strike? That might be difficult to explain as I think it comes from experience. Now different saws will behave differently, some straighten easily while others tend to need more attention. I avoid striking on the very back edge of the saw (and of course I avoid hitting the teeth when working near them).
This illustration shows the pattern in which I strike the saw with the hammer, on a wooden anvil.
I hammer in a square pattern of a couple of blows next to each other near the back edge of the saw, then a couple just below. I avoid striking the saw in the same place (unless I am working on a dimple or small bulge) but spread the blows around to prevent ‘popping’ of the blade. That is when a dent reverses direction when struck with a hammer. These can be tricky and may require more attention to get things flat.
This saw was difficult to photograph, but the blade is now straight on both the back and the business side. It had a significant kink and other minor bends, but it took less than 40 hammer strikes to straighten out the blade. When striking the saw make sure it is laying as flat as possible on the anvil, this can be difficult with a bad bend. I can tell when a blow from the hammer does something as it ‘sounds’ more solid when struck. If it makes a bit of a ‘ringing sound’ then the blow probably didn’t do anything, it is when the blow ‘sounds solid’, that work is done.
I should mention that there are other methods for straightening metal by considering that the hammer blow will expand the metal on one side, so the work is done on the reverse side of the above mentioned technique. This particular method requires a metal anvil as the idea is to expand the metal by hammering. I have had some success with this method on other bent metal items, but I do not use it for saws.
I think that a craftsman should be familiar with their tools and know as much as possible about all things involved. The study of metallurgy, of geometry, of physics, of chemistry, of morphology, the macroscopic and even microscopic study can add to the arsenal of knowledge and understanding. Expose yourself to as much learning as you can, question experts and continue the quest, don’t limit yourself. Like Mark Twain said, ‘Don’t let Schooling interfere with your Education”