By varying the presence of interstitial atoms and the density of dislocations, a particular metal's hardness can be controlled. Although seemingly counter-intuitive, as the density of dislocations increases, there are more intersections created and consequently more anchor points. Similarly, as more interstitial atoms are added, more pinning points that impede the movements of dislocations are formed. As a result, the more anchor points added, the harder the material will become.

Can they be use on an old Craftsman joiner. Mine is about 30 years old and gets little use because of the pain of setting the knives.

Minimal disruption from nicks in knives. With high-speed steel knives, if you nick one of your blades, you either have to remove the blades and sharpen the set or try to slide the knives so that the nicked portions of the blade no longer align. This presents either a cost factor, hassle, or both. With spiral cutter heads, you rotate and are back in business. Plus, since the inserts are made of carbide, the likelihood of getting nicks in the cutters goes way down in the first place.

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I just got my first planer and jointer. Both are Wen with spiral heads. I waited for an Amazon Prime day special and got BOTH, and an extra set of replacement blades for both, for a little over $700. Their 3 knife versions were about the same, and on Prime day it was actually LESS than both 3 blade versions would have been normally. I am really happy with both of them, although they are spiral heads, and not helical, and not carbide. Glad I waited for a sale, too!

I have an old but beauty INCA over under 8.5" jointer/planner. In spite of having the gauges to set the knives this was pretty much a day long job. I bit the bullet and bought a SHELIX replacement head sold by BYRD Tools. Due to the age of my machine it was a custom order. It took some effort=time to install but in the end what a difference. I buy my lumber in the rough and the first job after installation was a Lacewood and Black Walnut box. It machined the figured wood with no problem or tear out. I was so impressed that i immediately ordered a head for my dewalt thickness planner. i am equally pleased here. Noised factor is greatly reduced as you are not turning a solid blade through the air. With the cutters the air can move with less effort between them resulting in less resistance and hence less noise. My only knock on the cutters is that they tend to snipe a bit more than blades. It is an easy solution on the thickness planer by passing a sacrificial piece behind your good wood. Not so easy on the jointer. I have checked my tables and they are aligned so right now i simply leave a little extra length to be trimmed at the miter station. In the end what sold me was the ease of changing the cutter heads especially when you get the inevitable nick in a nice new set of blades. Even if you are simply a weekend warrior the price is justifiable. Think of it this way . With 4 rotations per cutter, you may never have to buy another set of blades.

Hardness of steelincreases if it contains

I've been a hobbyist woodworker for 40+years. I just upgraded my planer ($1200) and jointer ($650) with helical cutter heads. Wish I had done it a decade ago. However, the price was always the deterrent. Every manufacturer that sells to "hobbyists" gouges them. ("Get as much money as you can as fast as you can" and "What the market will bear" are their mantras.) Any reasonable comparison with similar machine tooling removes any legitimate, (or honest), defense of the prices for this tooling. Nevertheless, if you are a professional, or you are someone for whom "money is no object", OR you are just old and retired and have decided that you 'deserve' the performance in spite of the gouging, GET one of these cutter heads. You WILL appreciate it. And if you're not happy with the performance of the new head, (ignoring the cost), you are doing something wrong.

Better surface on figured wood. This is the point that seems to get all the attention around the internet. From my standpoint, I have used a jointer with HSS knives for over a decade and have had good results when face jointing figured stock, provided my knives are sharp and set properly, the jointer is tuned, and I take light cuts with a slow feed rate. I don’t rely on a jointer for a finish-ready surface, so even with a spiral cutter head, I will continue to scrape or sand to a final surface. The results I have seen so far using a spiral cutter head on figured wood have been spectacular. I have face-jointed birds-eye maple, curly birch, quilted maple, and quarter-sawn white oak, all with great results.

Helical vs. Spiral. When looking into spiral cutter heads, you will hear the terms “spiral” and “helical” used nearly interchangeably, but there is a slight difference between these two designs. Both designs feature a machined steel head with small square cutters placed along the surface in a spiral pattern. The primary difference lies in the orientation of each cutter. Spiral cutter heads position each blade, so the active cutting edge is perpendicular to the jointer’s feed direction. This would be a similar cutting action to a hand plane, taking a cut straight into a piece of the wood grain.

thehardness of steelincreases if it contains ans. pearlite martensite cementite austenite

In solid mechanics, solids generally have three responses to force, depending on the amount of force and the type of material:

The toughness of a material is the maximum amount of energy it can absorb before fracturing, which is different from the amount of force that can be applied. Toughness tends to be small for brittle materials, because elastic and plastic deformations allow materials to absorb large amounts of energy.

Mildsteel hardnessRockwell C

What do you think? Are you using a spiral cutter head in your jointer? If so, let us know why you bought it and what you think of it in the comments section below. Questions? Please feel free to post those in the discussion forum so we can continue to add to the knowledge base that is growing there.

The key to understanding the mechanism behind hardness is understanding the metallic microstructure, or the structure and arrangement of the atoms at the atomic level. In fact, most important metallic properties critical to the manufacturing of today’s goods are determined by the microstructure of a material.[7] At the atomic level, the atoms in a metal are arranged in an orderly three-dimensional array called a crystal lattice. In reality, however, a given specimen of a metal likely never contains a consistent single crystal lattice. A given sample of metal will contain many grains, with each grain having a fairly consistent array pattern. At an even smaller scale, each grain contains irregularities.

My shaper and planer are older knife style. Where can I find out whether or not they are compatible for replacement with either the spiral or helix cutter heads? Is there a model chart of compatibility available?

Rebound hardness, also known as dynamic hardness, measures the height of the "bounce" of a diamond-tipped hammer dropped from a fixed height onto a material. This type of hardness is related to elasticity. The device used to take this measurement is known as a scleroscope.[3] Two scales that measures rebound hardness are the Leeb rebound hardness test and Bennett hardness scale. Ultrasonic Contact Impedance (UCI) method determines hardness by measuring the frequency of an oscillating rod. The rod consists of a metal shaft with vibrating element and a pyramid-shaped diamond mounted on one end.[4]

Steel hardnessHRC

Quieter. The spiral cutter heads operate much more quietly than knife-based cutter heads. Although I don’t own a sound level meter, I can’t quantify this, but the difference to my ears is pretty dramatic.

Super easy cutter changes. Depending upon the design of a given cutter head, swapping out knives can be a cumbersome, time-consuming process. With spiral cutter heads, the process could not be much simpler. Remove one screw, rotate the cutter 90 degrees to a new edge, tighten it down, and resume jointing.

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Careful note should be taken of the relationship between a hardness number and the stress-strain curve exhibited by the material. The latter, which is conventionally obtained via tensile testing, captures the full plasticity response of the material (which is in most cases a metal). It is in fact a dependence of the (true) von Mises plastic strain on the (true) von Mises stress, but this is readily obtained from a nominal stress – nominal strain curve (in the pre-necking regime), which is the immediate outcome of a tensile test. This relationship can be used to describe how the material will respond to almost any loading situation, often by using the Finite Element Method (FEM). This applies to the outcome of an indentation test (with a given size and shape of indenter, and a given applied load).

Brittleness, in technical usage, is the tendency of a material to fracture with very little or no detectable plastic deformation beforehand. Thus in technical terms, a material can be both brittle and strong. In everyday usage "brittleness" usually refers to the tendency to fracture under a small amount of force, which exhibits both brittleness and a lack of strength (in the technical sense). For perfectly brittle materials, yield strength and ultimate strength are the same, because they do not experience detectable plastic deformation. The opposite of brittleness is ductility.

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Hardness of steelMohs

There are two types of irregularities at the grain level of the microstructure that are responsible for the hardness of the material. These irregularities are point defects and line defects. A point defect is an irregularity located at a single lattice site inside of the overall three-dimensional lattice of the grain. There are three main point defects. If there is an atom missing from the array, a vacancy defect is formed. If there is a different type of atom at the lattice site that should normally be occupied by a metal atom, a substitutional defect is formed. If there exists an atom in a site where there should normally not be, an interstitial defect is formed. This is possible because space exists between atoms in a crystal lattice. While point defects are irregularities at a single site in the crystal lattice, line defects are irregularities on a plane of atoms. Dislocations are a type of line defect involving the misalignment of these planes. In the case of an edge dislocation, a half plane of atoms is wedged between two planes of atoms. In the case of a screw dislocation two planes of atoms are offset with a helical array running between them.[8]

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Nope, that’s certainly not your grandpa’s jointer cutter head. It’s called a spiral cutter head. It is a newer design that uses the concept of insert tooling rather than traditional straight knives installed in the cutter head. Small square carbide cutters are placed near one another along a machined spiral pattern in a steelhead. This same technology is also available for other tools, such as planers, shapers, and molders. Still, since the purchasing criteria may differ for these applications, I will focus on using spiral cutter heads in jointers for this article. Spiral cutter heads are considered an upgrade for a jointer and generally carry a premium of $300 to $1,700, depending upon the size of your cutter head. Many manufacturers now offer this as an option that can be factory installed in their jointers when initially purchased. They are also available as a retrofit that you can install yourself. They are superior to traditional knife-based cutter heads in nearly every respect. Whether it makes sense for an individual to purchase one depends on whether the incremental cost is worth it to that particular woodworker, given their specific requirements. To evaluate whether or not it is worth the money to you, here are some of the key benefits to consider:

HRC full form inhardness

Helix cutter heads, on the other hand, operate more like a sheer or skew cut taken with a hand plane, as the cutters are positioned at an angle to the feed rate. Theoretically, this shearing action should provide a superior finish, as it does with a sheer cut on a hand plane. In practice, however, when applying a slow feed rate and a shallow cut, the surfaces produced on a figured stock by each style cutter head are nearly perfect to the naked eye, so it isn’t easy to substantiate a claim that one is better than the other without employing some level of magnification. And at that point, it becomes a science project rather than a meaningful measure of woodworking precision or productivity, which causes me to lose interest.

Another tool used to make these tests is the pocket hardness tester. This tool consists of a scale arm with graduated markings attached to a four-wheeled carriage. A scratch tool with a sharp rim is mounted at a predetermined angle to the testing surface. In order to use it a weight of known mass is added to the scale arm at one of the graduated markings, the tool is then drawn across the test surface. The use of the weight and markings allows a known pressure to be applied without the need for complicated machinery.[2]

In glasses, hardness seems to depend linearly on the number of topological constraints acting between the atoms of the network.[9] Hence, the rigidity theory has allowed predicting hardness values with respect to composition.

And no tear out. You can pretty much forget about grain direction. This is a huge deal, and extremely important on figured woods. (At least with Shelix.)

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This chart shows decimal inch equivalents for fractional inch, wire size, letter size and metric drill bits up to two inches in diameter.

I do a lot of work with Teak and as most folks know, teak is very destructive on sharp steel due to the silica in the wood. I traded in my jointer for a new jointer with a spiral head.... Worked so well that I also bought a new planer with a spiral cutter head. My large band saw even has carbide tips on the blade. Carbide is the only way to go in my opinion.

Indentation hardness measures the resistance of a sample to material deformation due to a constant compression load from a sharp object. Tests for indentation hardness are primarily used in engineering and metallurgy. The tests work on the basic premise of measuring the critical dimensions of an indentation left by a specifically dimensioned and loaded indenter. Common indentation hardness scales are Rockwell, Vickers, Shore, and Brinell, amongst others.

Strength is a measure of the extent of a material's elastic range, or elastic and plastic ranges together. This is quantified as compressive strength, shear strength, tensile strength depending on the direction of the forces involved. Ultimate strength is an engineering measure of the maximum load a part of a specific material and geometry can withstand.

The way to inhibit the movement of planes of atoms, and thus make them harder, involves the interaction of dislocations with each other and interstitial atoms. When a dislocation intersects with a second dislocation, it can no longer traverse through the crystal lattice. The intersection of dislocations creates an anchor point and does not allow the planes of atoms to continue to slip over one another[10] A dislocation can also be anchored by the interaction with interstitial atoms. If a dislocation comes in contact with two or more interstitial atoms, the slip of the planes will again be disrupted. The interstitial atoms create anchor points, or pinning points, in the same manner as intersecting dislocations.

In materials science, hardness (antonym: softness) is a measure of the resistance to localized plastic deformation, such as an indentation (over an area) or a scratch (linear), induced mechanically either by pressing or abrasion. In general, different materials differ in their hardness; for example hard metals such as titanium and beryllium are harder than soft metals such as sodium and metallic tin, or wood and common plastics. Macroscopic hardness is generally characterized by strong intermolecular bonds, but the behavior of solid materials under force is complex; therefore, hardness can be measured in different ways, such as scratch hardness, indentation hardness, and rebound hardness. Hardness is dependent on ductility, elastic stiffness, plasticity, strain, strength, toughness, viscoelasticity, and viscosity. Common examples of hard matter are ceramics, concrete, certain metals, and superhard materials, which can be contrasted with soft matter.

Scratch hardness is the measure of how resistant a sample is to fracture or permanent plastic deformation due to friction from a sharp object.[1] The principle is that an object made of a harder material will scratch an object made of a softer material. When testing coatings, scratch hardness refers to the force necessary to cut through the film to the substrate. The most common test is Mohs scale, which is used in mineralogy. One tool to make this measurement is the sclerometer.

However, while a hardness number thus depends on the stress-strain relationship, inferring the latter from the former is far from simple and is not attempted in any rigorous way during conventional hardness testing. (In fact, the Indentation Plastometry technique, which involves iterative FEM modelling of an indentation test, does allow a stress-strain curve to be obtained via indentation, but this is outside the scope of conventional hardness testing.) A hardness number is just a semi-quantitative indicator of the resistance to plastic deformation. Although hardness is defined in a similar way for most types of test – usually as the load divided by the contact area – the numbers obtained for a particular material are different for different types of test, and even for the same test with different applied loads. Attempts are sometimes made[11][12][13][14][15] to identify simple analytical expressions that allow features of the stress-strain curve, particularly the yield stress and Ultimate Tensile Stress (UTS), to be obtained from a particular type of hardness number. However, these are all based on empirical correlations, often specific to particular types of alloy: even with such a limitation, the values obtained are often quite unreliable. The underlying problem is that metals with a range of combinations of yield stress and work hardening characteristics can exhibit the same hardness number. The use of hardness numbers for any quantitative purpose should, at best, be approached with considerable caution.

Setting knives can be frustrating. This can take a while and lead to inconsistent results in getting the knives consistently set to the perfect height. Of all the factors to consider with spiral cutter heads, this one appeals to me the most, as I am not a fan of swapping knives in a jointer.

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HRC meaning inhardness

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I currently own one jointer and one thicknesser, both made by Invicta/Delta in Brazil about 30 years ago and still perform very well. I changed the cutterheads of both machines by also made in Brazil helical carbide cutterheads. I think all your remarks about these cutterheads absolutely true and I am very happy with them in spite of the cost. I am a weekend woodworker and really don't need superior machines but rewarding myself with these upgrades made me feel very good, fixing blades is in the past and I have more time to really enjoy woodworking.

Hardness of steel depends onmcq

Easier dust collection. A minor benefit is that the smaller cutters on spiral cutter heads break the material into smaller pieces, so slightly less suction is required to extract the waste back to a central system.

Dislocations provide a mechanism for planes of atoms to slip and thus a method for plastic or permanent deformation.[7] Planes of atoms can flip from one side of the dislocation to the other effectively allowing the dislocation to traverse through the material and the material to deform permanently. The movement allowed by these dislocations causes a decrease in the material's hardness.

There are three main types of hardness measurements: scratch, indentation, and rebound. Within each of these classes of measurement there are individual measurement scales. For practical reasons conversion tables are used to convert between one scale and another.

This upgrade is a no-brainer for professional woodworkers who use their jointer. Minimized downtime due to blade swaps, less sanding time on face jointed surfaces, and fewer sharpening expenses add to real savings and competitive advantage due to better productivity.

Joint MDF or plywood. If you ever have a requirement to join man-made materials such as MDF or plywood, you can do this with confidence using a carbide insert cutter head, while this is not recommended with traditional knives (although I will admit that I have jointed plywood with knives a time or two).

Edge longevity. Spiral cutter heads utilize carbide steel inserts, while most knife-based cutter heads incorporate knives made of high-speed steel. Carbide normally holds an edge for at least three times as long as high-speed steel, much longer than that in many cases. This translates to less time between swapping out cutters. Plus, the insert cutters for spiral cutter heads normally have four cutting edges on each one, so if one gets dull, it can be rotated, and the jointer is immediately back in production. Depending upon the cost of sharpening and replacing knives in your area, it is unlikely that this longevity advantage alone will ever singlehandedly justify the cost of the spiral cutter upgrade. Still, it is a factor that can offset some of the price differentials, so it is worth consideration.

There are five hardening processes: Hall-Petch strengthening, work hardening, solid solution strengthening, precipitation hardening, and martensitic transformation.

Hardness increases with decreasing particle size. This is known as the Hall-Petch relationship. However, below a critical grain-size, hardness decreases with decreasing grain size. This is known as the inverse Hall-Petch effect.

Hardness of a material to deformation is dependent on its microdurability or small-scale shear modulus in any direction, not to any rigidity or stiffness properties such as its bulk modulus or Young's modulus. Stiffness is often confused for hardness.[5][6] Some materials are stiffer than diamond (e.g. osmium) but are not harder, and are prone to spalling and flaking in squamose or acicular habits.

Decisions, Decisions. Is a spiral cutter head right for you? Considering this upgrade, the following simple table might help you determine the trade-offs.

I like the concept behind spiral and helical cutter heads, and I took the plunge and ordered one with my recent jointer purchase. As a hobbyist, I consider this a luxurious indulgence. I need to use a jointer more to justify the expense based on any cost savings I will incur down the road. But the surface quality, quieter operation, ease of blade change, etc., make it an attractive upgrade for any woodworker who can afford one without cutting into grocery money.