Tell us about yourself!
When I put clay onto the blade I go about half way up the tang in order to leave a section of metal to hold onto with the pliers when I do the heat treatment. When I quench the blade the blade I only dip the section with clay on it into the oil and allow the rest of the tang air cool, thus the tangs of the blades aren't hardened and remain soft.Sorry about the confusion and thanks for pointing it out, I will add in a brief sentence or two to clear this up in the Instructable.
Wow thanks for the long reply. I am going to break up my response into a couple sections for this:Firstly I would like to thank you for the thought and curiosity you have into different types of metals that are available. I am a chemical engineer and I have done metallurgy courses so I am actually quite familiar with the topic. I agree with you that in an ideal world you could just google the brand of lawn mower blade and a nice spreadsheet of metallurgical information would appear but for most brands this really isn't the case, most of the lawn mower blades I have come across aren't actually branded by whomever made them (they simply have a manufacturers number) and most companies don't give the actual metals composition/grade on websites. So when I get a bunch of blades from a hardwar...
Wow thanks for the long reply. I am going to break up my response into a couple sections for this:Firstly I would like to thank you for the thought and curiosity you have into different types of metals that are available. I am a chemical engineer and I have done metallurgy courses so I am actually quite familiar with the topic. I agree with you that in an ideal world you could just google the brand of lawn mower blade and a nice spreadsheet of metallurgical information would appear but for most brands this really isn't the case, most of the lawn mower blades I have come across aren't actually branded by whomever made them (they simply have a manufacturers number) and most companies don't give the actual metals composition/grade on websites. So when I get a bunch of blades from a hardware store it really is a lucky dip of them and I don't spend much time trying to look for information that isn't available.Next in terms of how metals are handled and the "heat treatment" already on lawn mower blades. Most manufacturers like to brand their products with terminology of how amazing their blades are but you have to remember that what they are aiming for in a lawn mower blade and what we are aiming for in a knife are completely different. They want extremely soft blades as the risk of breakage when hitting a stone is a serious hazard, while we want fairly hard edges which will hold an edge and consequently are less durable. Thus there is little point in keeping most manufacturers already done heat treatment. I agree with you that each metal has it's own set of heat treatment guidelines and they make huge differences in how the metals qualities are determined, as you said "the days of the "heat it up to cherry red and toss it in old oil" are kind of dead and sort of long gone", but in practice this Instructable wasn't written for people that have access to temperature controlled furnaces which can be used for the ideal heat stands at the perfect temperature and who also want to spend a fair amount time firstly researching into different metals and selecting the best process. From a metallurgical standpoint if you want to achieve the correct heat treatment on a knife I would recommend going to a steel manufacturer or supplier getting a blank knife/bar from them of known composition and once you have shaped the blade send it back to them so that they can do the heat treatment for you. I wrote these instructions for people who want to have a more hands on experience, you may not get the perfect heat treatment but you do get the satisfaction of knowing that you made a knife from scratch using recycled metal.There are loads of instructions on the internet nowadays for making knives, blacksmithing and metalwork, there are also quite a few artisan blacksmiths and knife guilds all of which can help guide a person to making there own knife. My instructions are written for hobbyists who may just need some rough ideas on how to go about knife making and the steps involved, I didn't go into lots of detail with most of the steps as the instruction would turn from being a quick read into a truly massive research article and frankly if you don't understand something or if you want to know more on a topic you can always google it. This brief writing style also applies to heat treatment which is a massive body of work and impossible to write up in a few simple lines, the methods I used are based off my reading up on using recovered metal of unknown composition and what tools and equipment I had readily available at home.This Instructable was written up to follow my method of knife making and not to claim that it is the best method. When it comes to the final knife in my hand I am proud of my work and like the end result and frankly if it doesn't hold an edge forever I can live with having to sharpen it every now and again.
The first picture with step 5 shows when I had just put the clay on and it was still soft. The electronic parts were just used to hold the knives in place and prevent them from tipping sideways. There aren't any electrical processes that need to be done with the heat treatment.
Most alloys nowadays are pretty standard and don't have high levels of impurities, so a standard piece of iron or steel is unlikely to have any lead in it. Lead is a really soft metal so it wouldn't make a good lawn mower blade, it also has a very low melting point so you would be able to tell its lead almost instantly. The main metals to be careful with when doing home metalwork is anything which has been electro-plated with zinc or chrome (looks shiny and is "rust" resistant) as these can give off toxic fumes. That being said never do metalwork indoors as fumes from either the metal or the fire can be toxic in high concentrations.
Lawn Mower Blade to Custom ...View Instructable »
You have made a truly amazing ring. One bit of advice if you make another is to dilute the Ferric chloride down so that it works slower, this lets you control the amount of etching that occurs.
The egg timer is a silicon/plastic ball the size of an egg which slowly changes colour as it heats up. You place it in the pot with the eggs and when the colour change reaches the desired mark on the red card inside you know how cooked the eggs are.