I know this is not a wood posting, but I thought I would post something on metals. Specifically, tool steels. This will get a bit “in the weeds” but hopefully this will help some who never give tool steel much thought a new perspective on steel. In the last 20 years of my career, I do a fair amount of steel work, modifications of machines and creating jigs to assist installers in making install process more efficient. This required me to understand a lot more about steel than I ever planned on in my life.
Apologies to those who already know most of this. Please understand I will make some very basic broad comments for this conversation, let’s not get too myopic….
Basics on iron vs. steel:
Iron is an element (#26) vs steel which is an alloy (usually iron and carbon)
Other materials are mixed with iron and carbon to make a variety of harder steels.
Chromium, Cobalt, Manganese, Vanadium, Tungsten, Carbide plus a bunch of other minerals and metals are used to make steel stronger for tooling.
Enough of the pre-ramble --- Traditionally, hand tool steel for carpentry typically were a 3 types A, O, and W. Each letter defined how the metal was strengthened. Hardening steel is done by heating and cooling in a certain way to cause the molecules to align tighter together to make the metal more dense, ergo stronger.
This process is known as quenching and tempering. The key difference between quenching and tempering is that the quenching is rapid cooling of the steel piece, whereas tempering is heat-treating a steel piece and letting it air cool slowly at a prescribed rate. Quenching and Tempering are important processes that are used to strengthen and harden steel.
A = Air quenched --- O = Oil quenched --- W = Water quenched
Early 19th century tools mostly used water quenched steel. It was easily available, easy to sharpen, sharpened nicely, but did not hold and edge as long as other later steels.
Today, we have so many types of steels and alloys it is confusing.
The two tools I will focus on are high speed Drill bits and Chisels.
Drill bits ……*sigh* so many to choose from, so many brands. The most common ones we see are:
High speed steel (silvery), Black oxide (well black), Cobalt (kinda brassy goldish), Titanium nitride coated (brassy colored) and Carbide.
Titanium Nitride (TN) coating are those brass colored drill bits we all see everywhere. The TN coating lowers the friction which in turn, makes the drill bit perform better. The stuff does work, BUT, here is the issue – the coating is applied to a high speed steel bit and if the quality of that steel is suspect, then once the coating begins to wear down the bit really begins to fail. For a woodworker most will not notice since wood is so much softer than steel, and the TN coating helps in lowering the heat up and burning of the hole being cut. When cutting steel though you will notice it quickly. Most the bits coming from China are mostly likely getting their drill stock all from the same manufacturer. This probably explains why we periodically get bad batches of drill bits across the brand names from time to time (Think Dewalt, Milwaukee, Bosch…etc.).
Anyway, what causes bad steel batching ? most common is poor Q.C. when they are alloying the steel or more common, incomplete or poor tempering process. You see, when tempering steel, you need to heat up and then cool down, but once it is cool typically there can remain imbalanced tension within the steel. This can cause the steel to get micro fracturing and or cause the steel to have inconstant tempering though the metal. It also can cause the metal to twist. To prevent this, usually you need to heat up a second or third time at lower temperatures to ease out that tension. Time is money so many makers do a short cut version of this.
Cobalt steel typically has Cobalt alloyed into the steel with a variety of other mineral and metal recipes.
You might see it called M42, M2 M36 or maybe 8% or 6%. These bits are better and harder and can drill through High Speed Steel if done correctly.
Carbide bits are made from Carbide, tungsten and nitrides typically. These bits are Brittle, but super hard and are use for going though tooling steel or other metals that are hard. Rarely used by woodworkers. Carbide tipped bits are the ones we use for drilling through stone or concrete. The carbide is welded to a HSS shank so only the tip is Carbide.
Diamond coated bits are used for glass and or ceramic, or precious stones.
EACH material has a drill cutting speed that is optimum. Basically, the harder the material the slower the rotation of the bit. So, Stainless steel (no lubricant added) is usually 50-500 rpm range, HS steel is usually 60-850 range (use lubricant). But, most of us just cut regular rolled 40-60,000 psi steel (A-36, a572). That said, most people run the bit way to fast which just burns up the bit and causes it to fail. This metal is usually cut 120-1200 range. All this is highly dependent on feed rate and metal thickness, or hole size. These numbers are for starting reference only. I recommend reading up on drilling speeds if you do a lot of steel drilling. Most HS bits are set at 118° or 131°. Both these can be very aggressive in wood so be careful when using these. A way to keep your Forstner bits lasting longer is if you have to drill though thick material, you can cut the 1st ½ inch with the Forstner then switch to a HS bit equal size, drill through until you are close to the other side then switch back to the Forstner. Just for reference a Black Oxide bit (and HS steel) point of heat failure (when the temper becomes compromised) is around 975F whereas, Cobalt is roughly 2850F. The Titaniuim Nitride coating helps keep the heat load down..
Enough on drill bits. Chisel steel, it is way easier to discuss and a shorter reference.
Basically, the most common metals we see with chisels are one of the following types.
O1 & A2 – Many brands use these such a Lie-Nielsen and Lee Valley.
Chromium Vanadium (CV) – To be found in brands like Irwin, Some German Chisels brands and others.
Chromium Manganese (CM)- Narex and some Japanese chisels.
PM V11, D2 – Special steel. These hold a better edge longer but can be tricky to sharpen.
All of these steels have their pros and cons. A2 and PM-V11′s tends to be better at edge retention. O1, CV and CM seem to be easier to sharpen than A2 or PM-V11. This is pretty subjective though. To me, getting the back flat is the hardest part of sharpening regimes. Once sharpened correctly, keeping the edge is easy to do. This is why I keep “butcher chisels” in my tool box. Anytime I might be near metal or other hard surfaces that could damage a chisel edge I use those. I machine sharpen those.
Got pretty long winded there, one final thought though:
In my opinion, most Chinese HS steel is too inconsistent in its to be used for accurate machining or seriously considered for real high end tools.. Not really a woodworker’s problem, but whenever possible, get North American, Japanese or European steel. A Shout out to Czech, Portugal and Poland there are some pretty nice tooling from those countries that is decent quality being made.
I hope this help some gain a better insight to steel and the types we use in woodworking.
Apologies to those who already know most of this. Please understand I will make some very basic broad comments for this conversation, let’s not get too myopic….
Basics on iron vs. steel:
Iron is an element (#26) vs steel which is an alloy (usually iron and carbon)
Other materials are mixed with iron and carbon to make a variety of harder steels.
Chromium, Cobalt, Manganese, Vanadium, Tungsten, Carbide plus a bunch of other minerals and metals are used to make steel stronger for tooling.
Enough of the pre-ramble --- Traditionally, hand tool steel for carpentry typically were a 3 types A, O, and W. Each letter defined how the metal was strengthened. Hardening steel is done by heating and cooling in a certain way to cause the molecules to align tighter together to make the metal more dense, ergo stronger.
This process is known as quenching and tempering. The key difference between quenching and tempering is that the quenching is rapid cooling of the steel piece, whereas tempering is heat-treating a steel piece and letting it air cool slowly at a prescribed rate. Quenching and Tempering are important processes that are used to strengthen and harden steel.
A = Air quenched --- O = Oil quenched --- W = Water quenched
Early 19th century tools mostly used water quenched steel. It was easily available, easy to sharpen, sharpened nicely, but did not hold and edge as long as other later steels.
Today, we have so many types of steels and alloys it is confusing.
The two tools I will focus on are high speed Drill bits and Chisels.
Drill bits ……*sigh* so many to choose from, so many brands. The most common ones we see are:
High speed steel (silvery), Black oxide (well black), Cobalt (kinda brassy goldish), Titanium nitride coated (brassy colored) and Carbide.
Titanium Nitride (TN) coating are those brass colored drill bits we all see everywhere. The TN coating lowers the friction which in turn, makes the drill bit perform better. The stuff does work, BUT, here is the issue – the coating is applied to a high speed steel bit and if the quality of that steel is suspect, then once the coating begins to wear down the bit really begins to fail. For a woodworker most will not notice since wood is so much softer than steel, and the TN coating helps in lowering the heat up and burning of the hole being cut. When cutting steel though you will notice it quickly. Most the bits coming from China are mostly likely getting their drill stock all from the same manufacturer. This probably explains why we periodically get bad batches of drill bits across the brand names from time to time (Think Dewalt, Milwaukee, Bosch…etc.).
Anyway, what causes bad steel batching ? most common is poor Q.C. when they are alloying the steel or more common, incomplete or poor tempering process. You see, when tempering steel, you need to heat up and then cool down, but once it is cool typically there can remain imbalanced tension within the steel. This can cause the steel to get micro fracturing and or cause the steel to have inconstant tempering though the metal. It also can cause the metal to twist. To prevent this, usually you need to heat up a second or third time at lower temperatures to ease out that tension. Time is money so many makers do a short cut version of this.
Cobalt steel typically has Cobalt alloyed into the steel with a variety of other mineral and metal recipes.
You might see it called M42, M2 M36 or maybe 8% or 6%. These bits are better and harder and can drill through High Speed Steel if done correctly.
Carbide bits are made from Carbide, tungsten and nitrides typically. These bits are Brittle, but super hard and are use for going though tooling steel or other metals that are hard. Rarely used by woodworkers. Carbide tipped bits are the ones we use for drilling through stone or concrete. The carbide is welded to a HSS shank so only the tip is Carbide.
Diamond coated bits are used for glass and or ceramic, or precious stones.
EACH material has a drill cutting speed that is optimum. Basically, the harder the material the slower the rotation of the bit. So, Stainless steel (no lubricant added) is usually 50-500 rpm range, HS steel is usually 60-850 range (use lubricant). But, most of us just cut regular rolled 40-60,000 psi steel (A-36, a572). That said, most people run the bit way to fast which just burns up the bit and causes it to fail. This metal is usually cut 120-1200 range. All this is highly dependent on feed rate and metal thickness, or hole size. These numbers are for starting reference only. I recommend reading up on drilling speeds if you do a lot of steel drilling. Most HS bits are set at 118° or 131°. Both these can be very aggressive in wood so be careful when using these. A way to keep your Forstner bits lasting longer is if you have to drill though thick material, you can cut the 1st ½ inch with the Forstner then switch to a HS bit equal size, drill through until you are close to the other side then switch back to the Forstner. Just for reference a Black Oxide bit (and HS steel) point of heat failure (when the temper becomes compromised) is around 975F whereas, Cobalt is roughly 2850F. The Titaniuim Nitride coating helps keep the heat load down..
Enough on drill bits. Chisel steel, it is way easier to discuss and a shorter reference.
Basically, the most common metals we see with chisels are one of the following types.
O1 & A2 – Many brands use these such a Lie-Nielsen and Lee Valley.
Chromium Vanadium (CV) – To be found in brands like Irwin, Some German Chisels brands and others.
Chromium Manganese (CM)- Narex and some Japanese chisels.
PM V11, D2 – Special steel. These hold a better edge longer but can be tricky to sharpen.
All of these steels have their pros and cons. A2 and PM-V11′s tends to be better at edge retention. O1, CV and CM seem to be easier to sharpen than A2 or PM-V11. This is pretty subjective though. To me, getting the back flat is the hardest part of sharpening regimes. Once sharpened correctly, keeping the edge is easy to do. This is why I keep “butcher chisels” in my tool box. Anytime I might be near metal or other hard surfaces that could damage a chisel edge I use those. I machine sharpen those.
Got pretty long winded there, one final thought though:
In my opinion, most Chinese HS steel is too inconsistent in its to be used for accurate machining or seriously considered for real high end tools.. Not really a woodworker’s problem, but whenever possible, get North American, Japanese or European steel. A Shout out to Czech, Portugal and Poland there are some pretty nice tooling from those countries that is decent quality being made.
I hope this help some gain a better insight to steel and the types we use in woodworking.
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