Making Our Own Turning Tools
It is reasonable for most woodturners to ask the question,
"Why would anyone want to make their own turning tool"? There are many answers. In the "Dark Ages" of woodturning
(prior to the mid-70s) we made our own turning tools because we had to. Today we make them because there are still shapes that we can't buy, they are less expensive than High Speed Steel (HSS) tools, and the durability of HSS may not be required for a specialty tool. Many find that making turning tools can be an enjoyable aspect of woodturning, and there is the satisfaction in being able to say, "I made it myself."
CARBON STEEL TOOLS FROM DRILL ROD
This discussion will describe how we can make a turning tool from drill rod. The necessary tools are a propane or MAP gas torch, a few fire-bricks, a small magnet, some 600-grit sandpaper, and a gallon of oil in a metal pail. Add a pair of safety glasses or face shield, a large pair of pliers for handling the hot steel and a heavy hammer for banging on it, and we are ready to make our own turning tools. Optional but very useful tools would include a metalworking vice, a 5" angle-grinder with a coarse wheel, a wire brush, and a pair of heavy leather welders' gloves.
The high carbon Drill Rod will make excellent round skews, small hollowing tools, and the Pyramid and Skewchi gouges. They can also be used to make a spindle gouge when we grind a flute into them at the tip. The tool will not be the equal of an M-2 High Speed Steel, but it will be a lot less expensive and a good source for those special tools that we use but occasionally.
It is quite easy to heat treat a high carbon tool steel. A round "oil hardening" drill rod with an
"O-1" designation can be found in various diameters at all steel warehouses and many welding supply dealers. A flat bar with a similar carbon content is available from steel warehouses. Do not expect to use the stock from the rack at Home Depot because it is a soft "mild steel" whose carbon content is not sufficient to support any efforts to harden it. Two on-line sources that I have used are listed below:
O, W, or A
Drill rod is designated by the medium that is used for quenching - oil, water, or air; and they are designated by the type prefix, O, W, or A, followed by a number that corresponds with the carbon content of the steel. Oil hardening
"O-type" steels have the advantage that they can be heated for bending, and then annealed to a soft condition for shaping and rough grinding, prior to continuing the heat treatment. Without any further discussion, I will just say that the
"O-1" and "O-2" drill rod is better suited for our tool making, and let the metallurgists who read this argue with me.
There are many advocates of the air hardening "A-type" steels because they are easier to use. However, they cannot be heated for bending, and annealed for shaping without altering their properties, and their final hardness is less predictable than with the
"O-type" steels. If anyone has experience with air-hardening steels and they are satisfied with the results, by all means, keep using them.
The water hardening "W-type" steels are considerably more expensive, and they present a safety hazard for burns from having hot steel and water in the same place at the same time. Anyone wishing to use one of these steels can do so by following these same directions, except that
"room temperature cold water" is substituted for "oil" as the quenching medium wherever it is used.
Since we are using an "oil hardening steel", we can use any oil from 30W motor oil
(non-detergent if you can find it) to Mineral Oil. The only difference is that the 30W may smoke and stink a lot, but it will be a lot less expensive than the Mineral Oil. A gallon of Chainsaw Bar Oil is a good compromise.
We can use a common propane torch as the heat source for most of our tool making, as long as we don't use steel whose cross-section is larger than that of a 3/8" rod. I would recommend using the higher temperatures of a MAP gas or Oxy-Acetylene flame for larger sections. It is possible to heat the end of a ½" rod with a propane flame, but it will take awhile, and it may be difficult to get it hot enough to bend if we need to do that.
We will be heating only the 3" or 4" on the end of the steel bar. Get 5 or 6 pieces of fire-brick from the local stove and fireplace supplier, and build a little box around the end of the steel to contain the heat from the torch.
Charcoal briquettes in the BBQ grill could provide sufficient heat, and it would give us the feeling of being the "Village Smithy" standing under the spreading Chestnut tree. However, this is not a good heat source because the presence of excess Carbon (the briquettes) will increase the carbon content of the steel at the surface of the rod, and make our tempering difficult to control. I prefer the torch because it is easier to use, not as messy, and it is less expensive than buying Charcoal Briquettes.
Step One - Bending
If we are making a hollowing tool, heat about 3" on the end of the rod until it is a bright red/orange color. Take it to a vice before it cools and use whatever means is necessary to make the bend. I use a pair of pliers on small rod and a heavy hammer on anything over ¼". If it doesn't bend easily, go back to the fire and heat it until it is a brighter orange color. This is a case where the hotter it is, the better, and the brighter orange the color, the hotter the steel.
Step Two - Annealing and Stress Relieving
This step will relieve any residual stresses from the bending and take the steel to a uniform soft "annealed" condition. Heat the end of the rod again until it is a bright red to orange color. A better way to control this temperature is to hold a magnet to the hot end of the rod. When the steel is no longer magnetic, you are at the proper temperature.
Leave the rod in place on the hot bricks and SLOWLY remove the flame. Do not move the steel until everything has cooled to room temperature and then it can be handled with the bare hands.
Step Three - Shaping
The steel is now soft, can easily be cut with a hacksaw, and shaped with a coarse wheel on the grinder. I recommend a 46-grit wheel for this because the surface of a finer wheel will rapidly become filled with the soft steel particles. A coarse wheel on a 5" angle-grinder is a good tool for rough forming the end of the rod.
If we have a ¼" or 3/8" wide grinding wheel that can be dressed to a radius, we can grind a shallow flute into the end of the rod. A 2" length is sufficient. The angle-grinder is good for this task while holding the rod in a vice.
Step Four - Hardening
We are now ready to begin the heat-treatment of the steel, and the first step is to "harden" the steel to the maximum hardness available for its carbon content.
Heat the steel to the same temperature as described for
Step Two - Annealing and Stress Relieving.
Immediately plunge the rod into the container of oil and stir it around in the oil for a minute or two. Remove the rod and let it cool to room temperature.
It is best to do the quenching outside because there may be some flashing of flame on the surface of the oil. This is a common thing to happen, and the flame will die as soon as the steel is submerged into the oil and it has cooled below the flash point of the oil.
Step Five - Tempering
The steel is now very hard and very brittle, and it must be "tempered" or "drawn" back to whatever hardness we desire for the cutting tool. Here is where we have to make the compromise between hardness and durability. If the tool is too hard, it will take a sharper edge, but it will be very brittle. Less hardness and the edge will not be as sharp, but it will not be brittle. Think of it as being similar to the difference between a razor blade (brittle) and a carving knife (durable).
An easy way to temper small pieces of steel is to place them in a pan of oil in a 425-450 degree oven for about 4-hours. Use an oven thermometer placed in the oil bath for accuracy, and set it at the bottom of this temperature range for a gouge and the upper end for a scraper. Then turn the oven off and let it cool before removing. If the oven cannot control the temperature of the oil or the pan will not fit, we will have to use the visual method.
The visual method can be tricky because we will be observing the changing color of the steel and being able to recognize what is called a "light straw yellow". That is the color of a polished steel surface when it has reached the 430°-450°F temperature range. I would recommend doing a trial run to become familiar with the color changes of the steel before doing the real thing.
Remove all of the black gunk and scale from the steel surface, and polish it with 600-grit until it has a smooth shiny surface. The more polished the surface, the easier it will be to see the color change. Slowly heat the steel with the propane torch while holding the tip of the torch 4-6" away from it. Move the flame around over the steel to insure uniform heating. Heat the steel slowly; otherwise, it will pass through the color changes to fast to see them.
Watch the shiny surface of the steel. It will slowly change color to a light yellow, to a more orange "straw yellow" color, to a bronze and finally blue. That first color change in the "light yellow" to "light yellow/orange" is the one we are looking for. If we are making a scraper tool, then we will want the darker "orange" color. Now go back to Step Four to re-harden the steel, and then temper it to the proper color. When the color is reached, remove the flame, and allow the steel to cool without moving it.
Step Six - Finish
Clean up the tool, sharpen it, and use it. After is has been ground back to the untreated area of the steel, do these same steps again.
OTHER SOURCES OF STEEL
They are a readily available source of a hardened steel, there have been a lot of articles published that describe using them, and every gathering of woodturners has at least one "expert" on the subject. This doesn't make them a safe woodturning tool, and I am an advocate of NOT using an old file for making a cutting tool. Yes, we can anneal, harden, and temper them just as we would another piece of high carbon steel. But, the difference is that every groove in the surface of the file is a stress concentration where a crack into the steel is waiting to start. Many of these files may already have hairline cracks that have started to migrate into the steel. We can grind the surfaces, and we can do all sorts of heat treatment to temper the steel to a useable hardness, but it is impossible to remove a hairline crack. We cannot see them, and it only takes one (1) to make it a dangerous tool.
Car and Truck Springs
Old car and truck springs are good quality high carbon steel that can be ground into scrapers and lance type tools without any heating or other treatment. I like a large tool and old truck springs make a good source of steel for them. I have several of these that were made in the days before there were such things as forged gouges and a Craft Supplies to sell them to us. The only caution is that it would be preferable to make all cuts with an abrasive cut-off wheel and not a torch. If the spring is burned to length with an Oxy-Acetylene torch, the composition of the steel in the cut area will be changed, and the steel will have to be ground back about 1/4" before using.
Boring bars and other tools can be made by drilling a 3/8" hole in the end or side of a 3/4" to 1" mild-steel bar or rod, and inserting various shapes of 1/4" square HSS tool bits. A 6-32 tapped hole and a setscrew will hold the bit in place. A HSS, 2-flute, ball end mill makes an excellent hollowing tool. These are available from Enco, MSC, and other sources.
- 3/8", BN End Mill, M-2 HSS, Part No. 320-3025, about $5.00
- Same in 10% Cobalt HSS, Part No. 320-3026, about $10.00
- ¼" Square x 2.5 OAL, M-2 HSS, Part. No. 383-5316, about $0.80
- Same in 10% Cobalt HSS, Part No. 383-5216, about $1.75
Discount Tools: http://www.discount-tools.com/
- 3/8", BN End Mill, Cobalt HSS, Part No. QUI-48520, about $10
Browse through either of these catalogs for other things that can be adapted for use as a woodturning tool.
One of my favorite turning tools is made from a .30-caliber rifle barrel. I have to give credit for this tool to Ted Bartholomew, of Tacoma Washington. The barrels can be available from a gunsmith for scrap price, and sometimes free. Drill out the end of the bore with a 3/8" drill, drill and tap for a set-screw, insert the 1/4" tool bit or 3/8" end-mill, and you have a high quality straight hollowing bar or turning tool.
Concrete Nails and Allen Wrenches
These are good sources for making tools for turning small objects and miniatures. Both are a high carbon steel that is very hard. Eye and face protection is an absolute when using concrete nails. They make a excellent tool because they are very hard, which also makes them quite brittle, and they are easily broken. They will not shatter like a file, but the flying piece can be an eye-hazard.
I am asked frequently about using Carbide for woodturning tools. While Carbide may last a lot longer, the particle sizes that make up the carbide prevent it from ever getting as sharp as a piece of tool steel. Using carbide is like having a steel tool that has been used for a while, but then it will never get any duller.
Carbide is useful for machining steel, but the mechanisms for cutting wood and steel are totally different and require different cutting tools. A microscopic crack propagates ahead of the cutting edge of a tool used for cutting steel, and the ability of the edge to withstand abrasion is more important than its absolute sharpness at the cutting edge. Wood is a flexible cellulose fiber has to be either cut or torn apart. The clean shearing cut that we use in woodturning requires a tool that is sharper than it is possible to get a piece of carbide.
Before anyone makes a reference to carbide tipped saw blades, remember that the saw blade is as far away as we can get from the proper shearing cut that we are trying to get with our turning tools. The closest thing that we have to a saw tooth, in either action or shape, is the parting-tool, which could be considered as a single tooth saw. In addition, the parting tool, whether used for end grain hollowing, as a lance for removing outside wood, or for parting, would be a good application for carbide tipped tools. The "Center Saver" tool systems, such as those made by McNaughton and Oneway, would also be a good application for a carbide tipped tool.
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