Proper heat treatment is an essential part of knife making, tool and die work, and parts fabrication. Without precise control of time and temperature, blades won’t hold their edge, and tools and parts may be too soft or too brittle for use. Buying a heat-treating kiln, oven or furnace can be a complicated process, but our job is to make it easy to navigate the decisions involved in finding the right one for your needs. Here’s some basic information to help you decide which is the best choice for your professional or hobby needs.
So, what is the difference? For our purposes, all three of these names refer to a fireproof box that gets hot. No matter what you call it “the box” needs to have the capability to get to the desired temperature and stay there for the prescribed amount of time. It also must to have the ability to heat and cool at the prescribed rate for the particular process required. Most importantly, it must be safe and easy to operate, and last a long time.
associated with the manufacturing of pottery, glass or ceramic ware. These are typically fired from room temperature to a specific process temperature at a prescribed rate of increase and then allowed to cool at a controlled rate back to room temperature. The rate of increase (or decrease) during the firing and cooling stages is often of great importance. Items being fired are seldom removed from the unit while it is performing. There may be periods of time when the temperature is held during the firing but the hold time relative to the total firing time is usually insignificant. Temperatures range from 1700° F – 2350° F.
Furnace: associated with forging or heat treating metal. These are typically HELD at a single temperature for an extended period of time. The exact rate of temperature increase during the heating stage is seldom of importance. Items being fired are often added to or removed from the furnace when the unit is hot. There are typically long periods of time when the temperature is held during the firing, and there may be multiple cooling steps and hold times for processes including annealing, case hardening, and tempering. Temperatures range from 2000° F – 2450° F.
Oven: associated with drying or cooking, are the same as furnaces except the usage temperature range is lower. The lower temperature rating often means a large chamber can be powered with lower amperage. Temperatures range from 250° F – 900° F.
It really doesn’t matter what you call it…. As long as it does what you need it to do. From this point forward, we’re going to refer to all the options as KILNS. What you really need to know is how much space you need, what temperature do you need to get to, and how long does it need to hold at that temperature.
Now, that we have that figured out... you need to think about:
What size do I need? A basic aspect to consider when choosing a kiln is its interior dimensions. Kilns for making knives are considerably smaller than other types of kilns because of the smaller size of the average project. Kiln size reduction helps to reduce costs as well as improve heating times. Determine the size of the largest blades you intend on creating and make sure it can fit inside your chosen kiln. It also depends on how big you want to work. There’s nothing worse than buying a kiln that you outgrow in 6 months. Think about the future and what you might grow into.
What temperatures do I need? Necessary temperatures are determined by the type of metal you work with, so make sure of your own requirements before buying a kiln. Check the above reference guide if you still have questions on heat treating temperatures.
What amperage does the kiln need 120V vs 240V and how many amps will the unit draw? Based on the size of kiln and top heat requirements, each kiln’s voltage requirements and amperage needs vary.
What type of controller do I need? A kiln controller is the brain that tell the kiln what to do, and when to do it. They range in simplicity, ease of operation, and price. Most of our heat-treating kilns have a variety of controller options that are determined by the manufacturer. Not all controllers are available through all manufacturers.
What safety features should I look for? All heat-treating kilns we sell have available door shut off devices cut power to the elements but leave the digital controller energized to resume the firing program as soon as the door has been closed. Check to see if your model has these included or if this is an add-on option.