How to Straighten and Tension a Bent Hand Saw

does this scene look familiar to you i think just about everyone who has ever used a handsaw has bent or kinked the saw blade at some point sometimes the blade springs back but sometimes it doesn't these saws are usually put away never to be seen or used again until someone inherits the useless tool or buys it at an estate sale for two to three dollars if you've ever been in this situation you may have wondered can this bent piece of metal be straightened into a usable saw again well i'm happy to tell you that the answer to that question is a resounding i've been sharpening hand saws for almost 20 years and i spent about 10 of those years as a part-time professional i've straightened hundreds of hand saws and each saw and each bend is a little bit different sometimes a saw can be hammered back to factory straightness other times it's best to get it straight enough to be usable but not try to go any farther than that in some cases a bend may be too severe or in too thin of an area of the blade and hammering any more than is necessary to make the saw usable again risks doing irreversible damage to the saw so i always warned my customers that there's a possibility that i may not be able to remove the bend completely this is especially true when the bend is in the thinnest area of the saw right up near the toe a typical handsaw blade tapers in thickness from thickest at the teeth near the heel of the saw to thinnest at the tip of the toe of the saw and this is so that the saw can run with less set i've always said that removing bends from a handsaw is just as much art as it is skill there's an awful lot of judgment in the process and as the old saying goes good judgment comes from experience but experience comes from bad judgment so my goal for today is to demonstrate the process that i use to straighten a handsaw but as i said earlier every saw and every bend is unique and really learning to do this is going to take practice so start with some saws that have no sentimental or collectible value because you will inevitably ruin a few saws before you've made enough bad judgments to gain the experience to make good judgment the tools required for straightening a handsaw are fairly basic you need a screwdriver that fits the screws on your saw precisely you need a hammer and you need some kind of anvil the hammer needs to have a smooth slightly rounded face to prevent you from damaging the saw with any hard corners i use two hammers i have a 24 ounce ball peeing hammer and i also have a 48 ounce drilling hammer sometimes called a lump hammer now you might think that these hammers are kind of large for the work on the contrary a large hammer allows me to use the weight of the hammer to do the work and i can gently tap on the saw blade rather than beating on the blade with heavy blows a large hammer offers more control as for the anvil you have lots of options you could certainly use a large heavy forged steel blacksmith's anvil but it's kind of unnecessary and a bit overkill just for sharpening saws a piece of railroad track from the scrap yard would work just as well you can also use the anvil on the back of a machinist's vise the anvil on my machinist vise was all i used for a good number of years when i operated my saw business and it worked just fine so if that's all you have feel free to use it as long as it's big enough to straighten the saws that you have today i use an inexpensive cast iron anvil now being made of cast iron it has no bounce like a forged steel blacksmith's anvil but for straightening saws that's actually a good thing one expert that i know of who's far more knowledgeable than i am insists that a dead anvil is actually more efficient than a blacksmith's live anvil when it comes to straightening saws because the dead anvil allows the steel to move more easily than a live anvil which would push back against the hammer countering the effects of the hammer strikes in fact my late friend steven shepard actually preferred end grain wooden anvils for straightening saws over iron or steel ones because the wood has more give than metal now of course hardwood is going to be a little bit better than soft wood however if all you have available is a cut off piece of 4x10 pine then use what you have so don't let anyone convince you that you need an expensive blacksmith's anvil to do this work unless you're going to be doing forge work a hardened steel anvil is completely unnecessary and may even be undesirable depending on who you talk to so before you start hammering away randomly at the blade it's important to assess the blade to determine where exactly the bend starts and ends now you can do this with a straight edge but after some time and some experience you'll be able to do it well enough by eye that you won't have to use the straight edge anymore it's also important to check it both from the tooth line and from the back of the blade because you want to know if there's any twist in the blade or if it's an even bend by checking from both the tooth line and the back you'll be able to tell if the blade is evenly bent or if there's some twist in it as it goes down sliding down this saw i can see that it's this has a slight s shape to it the major part of the bend coming here with a little bit more at the toe and if we flip it over we can also see that it has it's fairly consistent it maybe has a little tiny bit of twist in it because if you line it up just right you can see that the toe over here kind of sticks out to the right just a little bit more when when you're sighting down the spine of the saw and when we turn it this way you can see we cite right down the tooth line that now the toe kicks to the left just a little bit so there's a little bit of a twist at the toe so we're going to have to address that as well so since this blade has an s curve that tells me it has two bends in it it has one bend back here closer to the middle of the blade and then another bend closer to the toe now i'm going to have to address those two bends separately so i'll take care of the more severe bend first and that's the one that's closer to the middle of the blade and then once i get that one pretty straight then i'll address the bend at the toe now the twist to me looks like it's mostly at the toe so i'll address that when i get to addressing the less severe bend at the toe so we're going to start by addressing this more more severe bend here towards the middle of the blade after removing the handle from the blade i'm going to bend the blade in either direction now this may make the bends slightly better it may make them slightly worse or it may do nothing at all if it does nothing at all it tells me that the saw still has most of its tension in it if it makes the bend slightly better or slightly worse it tells me that the blade has lost some of its tension now i'm gonna have to put that tension back in if it has lost its tension and in any case i may have to retention the saw anyway after hammering it because hammering it is likely going to remove some of the tension but it's still good to give the saw a couple bends before you start hammering on it just to see because it it does release some of the stresses in the metal and it may show that the bend is either a little worse or a little better than you initially thought it would be now after assessing the tension and noting where the bends are i'm ready to start straightening this out now for your first couple of saws it may be helpful to use some soapstone or some chalk to actually mark the blade so you know where where you need to work on it in this case my bend is in this area and i'm going to be hammering in this area here and i'm going to start at the middle and work my way out towards the edges so i'll start hammering here and then work my way out so this bend this first bend here is in this direction right so this part of the saw this part of the metal has been stretched so in order to reverse this i need to stretch the metal on this side and compress the metal on this side and i'm going to do that you can see how it it sits up off the anvil so what i'm going to do is i'm actually going to flex the saw a little as i make these strikes and what you'll notice is that i'm not beating on the saw i'm just letting the hammer drop and i'm going to reassess each time and i'm going to repeat this process of giving the saw a little flex and then giving the saw a few taps and what i'm trying to do again is compress this side here and stretch this side here so again we're going to flex the saw a little and you can even reverse it and flex from here but as you notice it's a little harder to do so we'll flex from this side you can see my thumb pushing down so that it's flexing the blade and i make my hammer strikes starting in the middle and feathering out to the ends you'll notice i move the saw as i'm doing this so that i'm striking on the heavy part of the anvil so so after each set of hammer strikes i'm going to again sight down the blade to assess my progress before i start hammering again i want to see how close i'm getting once i start to get close to this section being back to straight i'm going to switch hammers to my smaller hammer this hammer has a smaller head so it's going to allow me to be a little bit more precise but it also has a lighter head so it's going to allow me to move less metal so i can be a little bit more precise with the work that i'm doing now there really is no formula to this as i said earlier every saw is different every bend is different so you're going to have to use a lot of judgment and this is where the judgment comes in how long do you keep hammering when do you stop so because there's really no formula for this and there's no way for me to tell you how long this is going to take there's no way that i can say do it this many times until your saw is straight you're just going to have to hammer check hammer check and just keep working and you may have to spread the area that you hammer out a little bit each time if your bend seems like it's getting a little better but maybe not quite better you may have to spread out that area that you hammer a little bit but keep working on it again you just use the weight of the hammer don't really strike it hard and continue to hammer and check hammer and check until you get most of the bend out so [Music] so now you can see that our first bend is pretty much taken care of there might be a hint of it remaining but sometimes you just kind of have to stop and say that that's enough so now i can work on that second bend near the toe and this one's going to be a little bit more fragile [Music] so here's where this blade ended up while it's not perfectly laser straight it's a marked improvement from where it was and i felt that any more hammering to the blade was just going to weaken it so i decided and it had about enough and it was time to stop but now it does need to be retention to retention the blade we want to make strikes just above the teeth of the blade and we want to do this alternating on either side so we'll make one here and then we'll make one here we'll make one here and then we'll make one here and you want to try and get as close to opposite of each other as you can and what this is going to do is it's going to help to straighten this tooth line just a little bit more and provide some rigidity to it so that when when the blade bends it doesn't come back it doesn't hold that bend it springs back to where it was so this is the next step or the final step in the straightening process now when i do this i'm going to use the ball peen the ball peen of the hammer and just like when i was straightening the saw when i'm doing the tensioning i'm constantly checking to make sure that the blade is staying straight or as straight as it was that i was able to get it if i happen to over tension one side it's going to bow that blade so i want to be very careful that i'm tensioning evenly on both sides in order to keep the blade straight if it starts to bow in one direction then you're going to need to add more tension to the other side so if the saw bows like this i'm going to add some more tension to this side and i want to keep that blade as straight as possible so now after tensioning again here's what the blade looks like again not perfect at the toe but the toe is a fragile area so you have to be careful not to over hammer there but what's important is i can bend this saw now and it springs back to where it was and it's nice and straight so this saw is ready to go so once the tension has been applied now this saw is ready to be cleaned polished if you're going to polish it and the teeth can then be sharpened and this can be a usable saw once again now as you saw this one didn't come out perfectly laser straight and that is going to be pretty common this is actually one of the more difficult ones that i've ever had to do it was an s curve it's a fairly thick steel fairly thick blade so um it was it was a little more challenging of a saw to do but it's at the point now where it's a usable tool once again whereas before the s curve was really just too pronounced and too much to be able to put this saw back to use so even though it's not laser straight it's straight enough to the point now that it's a usable saw it can be sharpened it can be put to use so i hope this has helped you a little bit this is quite a difficult topic to teach and it's also a bit of a challenging skill to learn but if you get yourself some old non-valuable saws and give it a try a few times practice a little bit you'll find that you too can do this it just takes a little bit of trial and error and a little bit of practice and you'll be able to straighten your saws as well

Channel: Bob Rozaieski

Views: 12,167

Rating: 4.9425054 out of 5

Keywords: Woodworking, Hand tools, Hand saw, Saw sharpening, Saw smithing, Saw straightening, Saw tensioning

Id: N_KikzIarLg

Length: 19min 55sec (1195 seconds)

Published: Fri Dec 04 2020