Rehardening My Plane Iron – Paul Sellers’ Blog

Was it cost-effective to reharden the plane iron after its many years of service? Of course, it was! Of course, it wasn’t. What made it well worth it is nothing to do with a financial cost but something I see as an intrinsic yet immeasurable value I consider imprinting yourself into an object you have gained from for long-term benefit. Not all objects will have this. Others will be of highly significant happenings still of great value. As will others, I have objects and remnants of wood that I will keep and pass on when the time comes. These hold valuable memories most might sweep away with the shavings, but they are deeper, much deeper than mere mementoes. The pine my hand made, round-both-ways plane developed specifically for shaping the inside hollows of Joseph’s cello front and backs is still in use but my main reason for enjoying it is thinking back to when we both made his cello., Another is the end of the turned column from one of the White House pieces and the extra ebony doorknob inlaid with a tiny remnant of President Harrison’s oak tree he planted back in 1889. I think I must own a thousand such things, along with tools I have pensioned off and to be used on special family pieces.

Since rehardening my plane iron I have returned it first to planing the mesquite on my cabinets and what a difference it made. None of the five planes I used held up particularly well and I include two North American premium plane makers in this too. Mesquite affects the cutting edges far worse than any wood I’ve ever used and know by many many times. The edges just give up, crumpling into a corrugated fracture as silica in the grain crunches the edges. I would say that it is an almost unique phenomenon to planing and chiselling mesquite but I know other less common and less used woods will be around in less temperate climates. After rehardening my now one-inch shorter plane iron the plane gave me the better service I’d hoped for with cleaner end grain surfaces many times over so for five minutes work it was more than worth the effort. After planing the end grain of mesquite many times along the tops of my doors, planing off an eighth of an inch of wood on one of the doors, I went on to plane knotted areas of sycamore with a glass-smooth success.

Of course, my objective is different than most. It’s what makes a difference to my world. One of my daughters-in-law made a comment a few years ago when she said what she admired about her husband was that when there was a need, he automatically thought make, repair not replace or buy first. Last week I needed something that would scrape the hollow inside a shallow bowl half an inch wide and an inch and a half long. I grabbed a 3/4″ washer, filed a bevel around the edge and scraped the hollow smooth. If I did such a thing regularly then, yes, I would just file a permanent quadrant on the corner of a scraper. But I did something even more. I drove a stick of wood through the washer which gave me a handle and I stopped partway through with the bevel on the far side of the new handle. The step created gave me something to pull against and I had a very decent tool to work with.

On the business of hardening and tempering. I have hardened in barbecue pits with charcoal, coke or coal using a hairdryer as a tuyere to get the temperature I need and have always had success in hardness. Sometimes I tempered the steel and sometimes not. I have tempered in the oven once and twice and have never noticed any difference. As it is with many things, things can get complicated by analysis alone and in your workshop making, shy of a new replacement cutting iron, the need drives and you simply harden the existing and get back to the real task in hand. When the need for strength is there, I would always temper and usually in two sessions of 90 minutes in close proximity to each step of hardening and then the temperings. Knives and chisels always need tempering to remove any brittleness and the risk of snapping. I don’t temper spokeshave irons but would if I had something else in the oven at the same time. Is tempering essential? Not really. Many things can influence your decision. Particular use, how much you plan to use it, what for, etc. Whereas I do value the input of metallurgists and engineers, they can and do complicate the intent of my output as do those who take my ideas and thoughts and add very complicated systems to it thinking they took a square frame and made a wheel from it. Why fix what ain’t broke? It worked exceptionally well for what it was intended.

I bought a new #4 plane iron via Amazon that fits any of the #4 plane brands but is made by Spear & Jackson for its own replacement blade. The cost was £5.77 and I bought it to test it out. It was finished out fine and flat. The hardness seemed just right and was hardened for the first 1 1/4″ (30mm). I am still in the test-at-the-bench phase but so far it took and holds a good working edge. At this price, it is worth buying for the steel alone as other blades can be made from it. I am thinking half a dozen plough plane cutters, spokeshave blades, knives etc. Anneal it, recut, drill and shape it and you’re on your way.

Here is a consideration you should think about. You could expect a bevel-up plane to stay sharper longer than a bevel-down version. Somehow pushing the cutting edge more directly into the wood should even out the pressure either side of the edge. You should also expect a better cut because of the different angle of presentation. But where the steel cuts the wood is so minimally different, in theory at least it should make almost no difference. On bevel-up planes, with a strong bevel of 30º added to a 12º incline, you have 42º at its installed bed angle. Now those usually involved in selling the planes always, always (emphasis added) say that the bevel of the cutting iron is 25º and whereas that is what they say, generally, it is a half-truth. By suggesting that the plane has a lower angle of presentation and then having a primary bevel of 25º, you might get the impression that the plane iron bevel is indeed 25º and therefore is giving a better cut when an additional 5º incline has indeed been added with a second bevel at the leading edge of bevel to strengthen the cutting edge and so in truth, we end up back at the 42º. Using a 25º bevel on any plane is not too practical: that edge is far more highly fractious and is barely viable for the high pressures and impact planing that planing always incurrs in the day-to-day. Watch for these sleight-of-hand nudges in the blurbs and sales pitch. Most sharp cutting edges are not merely ‘worn’ away, worn down, but more fractured away to result in a broken edge across the width according to the knots and hardness hit head-on. So we see that a shallow bevel of 25º readily fractures in any plane or chisel, spokeshave, etc but that does not mean we never use shallower bevels. Not at all! Where shallow bevels come into their own is when we use chisels at ultra-low angles in cuts we refer to as paring cuts. This is where we lay the chisel low to the wood surface on or near to the surface we need to pare into.

When we plane with the blade held in a plane or a spokeshave everything changes as it does when we use mallet blows on a chisel. I have gone as low as 20º for certain needs say for paring surfaces or using gouges in carving and such. The edge is very fragile at that low an angle and will not hold up to planing strokes or mallet blows but feeding pressures with the hands, arms and upper body maximise control of presentation and effort to expedite a felt-for cut. In a plane and for most chisels I never use less than 30º at my cutting edge simply because this has the intrinsic strength needed in the day-to-day. A bevel-down plane is always presented at 44-45º because it is indeed generally unalterable. So it’s just worth thinking about the dynamics of the presentation that’s all. Of course, the lower the angle of pitch the more inline the thrust cut and that does make a marginal difference. If the bed pitch could be 7º, I think that that could be the best but then the steel of the sole right at the back edge of the mouth would have no strength at so thin a point and would readily fracture and crumple.

Experiments are for establishing real value to our lives. Instead of relying on the views of others, we establish exactly what works best for us so its especially good in developing personal knowledge and ourselves. Many seemingly good reasons for doing things can be archaic and of no real value and I could quickly list a dozen off the top of my head ranging from plane types to scary-sharp type systems, the fallacies of bevel-ups over bevel-downs and vice versa. But of course, not too many people can test out or experiment with tools and equipment before they make a purchase or commit to something. Neither can we beg ten companies for planes to do an ‘Editor’s Favourite’ page or test ten plane irons to see which one is best for us. The fact is, many things influencing an editor’s choice are based on very little that matters in the reality of truer makers and not mere editors. My experience over the past 50 years reading magazines on woodworking is that their editors had little practical experience accumulated as makers. I’ve stopped reading them for health reasons!

It started out by me making wood work and became the long-term trial for how long a plane iron lasts a full-time woodworker using a plane six days a week for almost six decades. My feeling is that I am the only woodworker you know with this kind of working knowledge.

Experiments and tries lead us into establishing practical methods and techniques. I have established many simple solutions to my work area, tools, and equipment that simplify life, yes, but they also make me more efficient. When I decided to remove tablesaws and planers, chop saws and mortising machines it mostly came as a result of how best to work with woodworkers who would or could never own such things, never own the space for such things and who would never feel safe or competent in that kind of world. I was shocked to find that that was indeed a massive percentage of woodworkers. when considered on a worldwide scale. But even in say the more privileged environs, many woodworkers sought skill over speed and wanted the experience of working more closely with the wood than machines could ever possibly allow.

I mark my bench with mark for aligning my plane irons to the honing guide that guarantees easy setting of angles for abrading with a guide. It works for when I decide to use a guide instead of freehanding and it does not mean that I always stick to those markings. I often go in between the two marks of 25º and 30º to give me a different angle and not necessarily slap bang in the middle. By moving the chisel edge further from the honing guide I can set a shallower angle without using a protractor and beam. It’s fast and effective and encourages me to indeed experiment with angles for cutting edges. Because of this, I truly understand the establishment of 30º as a truly practical bevel. At this, my chisel compromises resistance and the amount of effort needed to effect a cut. Changing the bevel angle on a bevel-down plane blade a few degrees one way or the other makes no felt difference at the cutting edge, but on a bevel-up plane, it makes all the difference in the world. That being so, we should then see that a paring cut with a chisel is also affected by the steepness of the bevel at the cutting edge. It’s also worth noting that if you happened to lower the bevel on a bevel-down iron from 30º to 20““““““““““`º the cutting edge would fracture all the way along its length because there is no back support where it’s needed right above and behind the main cutting edge.

More on this tomorrow or this week at least!

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