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Posts Tagged ‘RiversWest’

On Saturday we began the heat treating process on the blades we shaped out two weeks ago.  When I arrived the electric furnace was already on and the first batch of tools was already inside. Here is the process we are using to heat treat the blades. This is the process Randy came up with after his research into the subject, and by his own admissions, parts of the process are not ideal for all blade types, but they represent a good middle ground for the blades we made and considering that we are using 01 tool steel.

Our blades were first heated to 1500 degrees Fahrenheit in the furnace. To make sure the blades were hot enough, a magnet was used. When the steel is hot enough, the magnet will not be attracted to it. The blades were taken out of the furnace one at a time using tongs and they were quenched in peanut oil. I am not sure why peanut oil specifically, but that is what we used. When quenching the metal, we were conscientious about getting the entire blade submerged quickly. If the blade is not submerged quickly, the oil around the blade will be heated to a high temperature and the metal which has not been submerged can ignite it.  For obvious reasons, this is not considered desirable. After the blade had been cooled quickly in the oil, making it very hard, the blade would be quickly toweled off and put into a toaster oven set to 350 degrees Fahrenheit to temper it.

The hardening makes the blade hard enough that the edges of the tools would be brittle. By heating them to 350 we changed the crystal make up of the metal, resulting in much tougher and more durable tools. Randy said 300 degrees would likely a better temperature to heat the skew chisels to considering that they are not designed to be used with mallets,  and that 400 might be better for the marking knife, but that 350 would be a nice compromise within the context of the class.

The previously described steps were completed in the class on Saturday. We were instructed to heat them again to around 300-325 for an hour or two to further refine the temper. The final stage for tempering process will be a cryogenic temper. That stage will occur in two weeks during the plane making class, where we will cool the blades in kerosene cooled with dry ice for 24 hours. Don’t ask me what the chemical changes are that occur, but it sounds pretty neat and should help us end up with some really nice hand made tools.

Here John and Jim are removing tools from the furnace and quenching them in the pot of peanut oil you can see at the bottom of the photo:Here are my blades after a little clean up. I have relieved both sides of the skew chisel here and tapered the tang to it into the handles I will be making:

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Last Saturday I took a one day class at our local sustainable small boat center; the RiversWest Small Craft Center. The center is a small member driven organization which you pay minimal dues to join ($50 per year), and which works to support the local sustainable small boat community through a variety of avenues, including the use of their library, tools, hosting classes, and with an additional monthly fee the ability to use one of their bays to build a boat.

This was the first class I have taken with them, and I was looking forward to learning some different techniques for tool making while also getting to know more of the members. It was taught by Randy, a member at RiversWest. The goal of the class was to make a Hock style plane blade with chip breaker, a marking knife blade, and a pair of skew chisel blades. Next month there will be another class where we will build a wooden plane body. For the plane body, there was the option to build a regular blade or to spend a little more time and make either a scrub plane or spar plane blade. I chose to stick with a straight blade during the class, though I would like to also build both other types at some point.

We started with several foot long lengths of 01 tool steel and cold rolled steel for the chip breaker which had been purchased from McMaster Carr. All the students had made basic jigs before the class which were used on the bed of a belt sander to establish the correct angles of the different bevels we would sand down in each of the blanks. My jigs were made from scraps of 2×4 and bits of leftover 1/4 inch thick cedar strips from building Abigail. The jig plans can be seen here.

To make the plane blade, I first ground the 30 degree bevel. With the bevel ground so that only about 1/32nd of and inch remained flat, I used the jig which had been made to drill a hole for each end of the slot in the middle using a light weight oil to keep the bit well lubricated and drilling each hole slowly. The next step was to drill a series of holes between the ends that either slightly overlapped or almost overlapped to remove the bulk of the material from the slot. A rat tail file was used to link the holes, and a flat file was used to straighten the sides. I was surprised at how little time it actually took to straighten the sides. The 45 degree bevel was ground next on the chip breaker. A hole was then drilled in it and tapped with a 1/4×20 thread tap. To dress things up, we used pennies to mark a radius on the back corners of the blade and chip breaker and those were ground. With that, the plane blade was ready for heat treating.

Next, I used the other jig to grind the bevels for the skew chisels and marking knife. The jig worked very well for the skew chisels, but left what seemed like an awfully obtuse angled spear front on the marking knife. To sharpen the angle of the marking knife spear point I held one side of the jig closer to the sanding belt to the other. That allowed me to change the angle of the edge to the side of the blade from about 60 degrees (so that where the two bevels came together the angle was about 120 degrees), to about 45 degrees, which resulted in about a 90 degree spearpoint which still seems a bit more obtuse than I would like, but I will give it a try and if it needs to be adjusted, I can do that. Though I did not get to it during the class, the sides of the skew chisel will need to be relieved near the blade, and I will need to grind the tang narrower to fit better into a handle.

Originally, the goal was to begin heat treating the blades during the class, but there was a wiring issue which would not allow us to plug in the oven we intended to use. That portion of the class will be completed in two weeks.

All told, I’d say the class was a success. My blades look great, and I look forward to being able to use them.

Here is Randy working on his chip breaker:

 

We cut some of the blades by hand before the bandsaw arrived:

 

Here are my blades:

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