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Skill Development: The Five Factors of Forge Welding
In the not too far past, blacksmiths held special positions in their communities because of the value of their tool and weapon making abilities. In more ancient cultures, the craft itself was considered a form of magic. Watching a blacksmith work is still mesmerizing and seeing a smith cause two pieces of metal become one through forge welding is indeed magical. To bring a bit of magic to your forge, there are five factors you need to consider; scarf, flux, temperature, timing and hammer blows.
A good scarf is the first and possibly the most important step in achieving a good weld. The scarf establishes the junction and provides the means for blending the weld. Start by upsetting the ends of the bar to provide mass. Create short, thick scarfs as thinner scarfs are subject to being burned away in the fire. Many feel a staggered scarf helps hold the flux and allows more bite but it’s a matter of preference. Once the scarf is built, remove the scale with a block brush to ensure a good, seamless weld.
Although it is possible to forge weld without flux, a good flux makes life easier. There are several good fluxes available commercially as well as a number of recipes for making your own flux. Some commercial fluxes have a bit of iron powder or scale mixed in, making it less slippery. No matter what flux you choose, you’ll want to prep your material by heating it until it begins to show color then wire brushing before sparingly applying flux to the edges that will touch. Preheating causes the flux to run better when the material reaches a welding heat. One note of caution, flux goes molten and will fly everywhere when you hit it. It is sticky when hot and can cause a nasty burn or even start a fire, so wear a leather apron, gloves and safety glasses.
It is essential that your material is evenly heated to a yellow heat which translates to a temperature of about 2,300 degrees. Orange means the metal isn’t hot enough, while white means it’s too hot. One trick you can use to gauge the temperature in a gas forge is to use the liner as a guide; when your metal blends with the hottest part of your forge, it’s at welding heat. The anvil face needs to be hot too; otherwise, it will steal the heat from your metal, giving you less working time. Finally, when working in a gas forge, turn your material over for a second right before you bring it out to even up the temperature.
When your material reaches the right temperature and is ready to weld, you have very little time to waste. Timing is largely a matter of practice, but it’s also a matter of being prepared – make sure the face of your anvil is clean and your hammer is in position before you pull your metal out of the forge. Place the material in the fire the way you want to bring it out, saving yourself the waste of readjusting your tongs. When you bring the material out, give it a quick tap to remove any excess flux, then be ready to hammer it as soon as it hits the anvil.
No matter what your mind tells you, hitting hard and fast won’t give you the weld you’re looking for. To prove the point, experienced smiths have tapped a weld together using a glass soda bottle. A firm blow or two in the center is enough to make the weld stick, then you can begin hammering with the same amount of force you would use to normally forge steel of that temperature. Be sure to work the thin tip of the scarf before it cools. Work both sides of your material, but avoid overworking it or forging beyond a medium orange heat.
If you’ve worked the magic properly, your weld will not have any dark spots or evidence of a scarf. If there is evidence that the weld is not complete, flux the open seams of the joint and take another welding heat, forging carefully so as not to reduce the stock beyond the parent stock.
Ta da, you have now passed one of the ancient rights of a blacksmith. If forge welding is still a bit of a mystery for you, check out Bob Heath’s book “How to Forge Weld on a Blacksmith’s Anvil For Those Who Have Diligently Tried and Failed.” Available at Pieh Tool for just $12.
Reprinted from Pieh Tool Company Legacy Links, October 2014
ASM is hosting an online section of their Heat Treater’s Guide: Practices and Procedures for Iron and Steels. It has tempering info, but it also has a lot of valuable charts.
This list describes some potential types of steel used in items commonly found in junkyards. This information was compiled from Machinery Handbook, Country Blacksmith, Blacksmith’s Journal, and Carpenter Technology Corp.
Machinery’s Handbook is an excellent source for heat treatment of these steels.
This article by Valentin Yotkov is an excellent primer on getting set up to add Repoussé and Chased items to your work. They can be stand-alone pieces or added to your iron projects to give them a unique appearance. (I’m presently visualizing copper floral accents on a forged iron table.)
As Valentine shows in the article, the basic tooling needed can be easily made, so the equipment costs are modest and you can make more specialized tools as your level of expertise increases.
We want to thank Valentin for giving GCBA permission to reprint this excellent article along with images from his studio in Brooklyn, New York.
Check out Tim LeMien’s creative restoration of an antique fire pot—donated years ago by D’everaux Coleman to Joe Rolfe’s Starr Homeplace Pandemonia Foundation.
There are two main types of transformation diagram that are helpful in selecting the optimum steel and processing route to achieve a given set of properties. These are Time-Temperature Transformation (TTT) and Continuous Cooling Transformation (CCT) diagrams. A full explanation and typical diagrams are illustrated here.
A calculator to generate the TTT or CCT of a particular steel is available here.
Follow the entire process here.
A Comparison of Abrasive Grit Sizes of Belts, Wheels, Stones and Hones.
For all you folks that are confused about abrasive grit sizes for your abrasive materials, this chart translates the US, European and Japanese grading systems and make sizing grit more comprehensible.
Free Online Blacksmithing Books
If you have difficulty accessing these sites (both located in England), try at different times of the day. These books are worth the effort.
Lining a Fire Pot
by Daniel Kretchmar
I got my clay out of several different holes in the ground at various reenactments. I have found that regular pure clay (no additives) will eventually crack, particularly if you are forge welding or getting a big fire going like we sometimes do for demos.
I have been making my own fire clay for a while now and it seems to work. I got the recipe from a book on how to make an adobe oven.
Take a lot of small dry irregular chunks of clay (1″ diameter or smaller), the smaller the better and fire them in your forge (a gas forge works best for this). If you don’t have a gas forge (which considering the thread, you likely don’t), broken clay garden pots work too! The trick is to get clay that has been fired already.
Break it into tiny pieces. I put on my boots and crushed them on the concrete floor. It doesn’t have to be powder, but it has to be smaller enough to stir. I also put fiber in mine for strength. I use natural rope fibers (manila/hemp/sisal/even grass clippings). I cut the rope into 1″ pieces and separate the threads.
My recipe is:
- 2 cups wet clay
- 1 cup white sandbox sand
- 1 cup crushed fired clay
- 1 loose quart of fiber rope cuttings
I mix until it is uniform. I add enough water that a 1″ ball of the mixture will deform slighty but stay together when being dropped from 4 feet off the ground. I then pack it just like Wes does using a hammer and a 2×4. I have several forges that have this lining that have lasted for years without any repair.
Dan also reminds us that a lot of the early forges were made from wood and covered with the clay liner.
I also remember smiths telling me that they mixed straw into the wet clay as a binding agent.
Steve Bloom of the Florida Artist Blacksmiths Assn.
Steve Bloom has created an archive of past issues of their newsletter “The Clinker Breaker” and a very large archive of articles of projects and tips from many other newsletters and other sources.
It’s well worth checking out.
The Florida Clinker Breaker newsletter archives of the Florida Artist Blacksmith Association
High Temperature Lube for Hot Punching
- Melt 1 cup of bees wax in a tin can, then slowly add about 2 cups of finely pulverized coal dust. Mix thoroughly.
- Let the mixture cool until solid, then punch a hole in the bottom of the can.
- Quickly heat the can until the cake slides out.
- Coat your hot working tools by rubbing the cake on the working surfaces.
Data to Help Understand Factors Affecting Heat Treating of Steels
The difference between Hardness and Hardenability
Explanation of Time-Temperature Transition and Continuous Cooling Transition Diagrams
Click Here for the Site
To improve your forge welds, use Anhydrous Borax, instead of 20 Mule Team borax.
Bob Patrick found that the 20 Mule Team folks add an anti-caking ingredient to their product, that melts at a higher temperature, and degrades the quality of the forge weld.
Click here to download a program to design and print your own graph paper.
Iron, Wood and Leather Finish
This is an updated 700 year old finish. It works great on iron, wood, leather.
- Use a double boiler to carefully melt bees wax.
- Add boiled linseed, oil, turpentine ( synthetic turpentine ), and finally Japan dryer. Proportions are 1 cup each and just 2 tablespoons of Japan dryer.
- Store in glass jars.
- Warm the material to be coated to facilitate penetration.
- Wipe excess off surface several minutes after applying finish.
- Remember to safely dispose of the towels or rags used to apply the finish, to avoid the posibility of spontaneous combustion
Super Quench Formula
Rob Gunther developed a safer alternative to lye quenching. It is usable on low and medium Carbon steels up to 1045.
To 5 gallons of water add:
- 5 lbs. of rock salt ( ice cream salt – not iodized)
- 32 oz of Dawn blue dish washing detergent
- 8 oz Shaklee Basic I ( a surfactant)
Make sure you stir the mix to dissolve all the salt, and also stir the mix every time before quenching. Heat the steel till non magnetic and then plunge into the super quench moving it rapidly in a figure 8 motion.
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