Saturday, December 24, 2011

More on Forge Welding

Forge Welding Tricks and Temperatures

Hello Mr. Robertson:

I very much enjoy your website ( as I am new to blacksmithing and value the articles as a learning resource.

My two questions deal with technique to follow when hand forge welding: Link

Q#1) I have used both a gas forge and an oxy/acetylene torch to heat small parts when I need to shape and forge weld tool steels (D2) to mild steels. From my research, I understand that the best forge welding occurs when steel temperatures are both above 2400F and when both surfaces are well cleaned. I have a very difficult time seeing the difference in color between dull yellow/orange, bright yellow and yellow/white to know when the materials are both hot enough to effectively weld. I have tried using "Tempsil crayons" to measure surface temperatures, but these crayons only indicate when surface conditions are above 1850F.
What trick or tool do you use to insure that both steel parts are adequately heated to guarantee a good quality forge weld?

There is a lot going on with a forge weld. You certainly need a high temperature and scrupulously clean all helps. At these temperature it is very hard to see and judge the colors of the steel. I usually tell people to look for a lemon yellow or melted butter color or the same color as the interior of the gas forge running at max. But there are some tricks that can be used.

The first one and will gain you the most success is to use special shade 2 welders glasses. Click Here for selection of Amazon Infra-dura safety glasses. I use either the infra-dura shade 2 or rose dydmium glasses for the forge welding. The infra-dura lens actually filters out more of the harsh light than the dydimium. Both of these lenses allow you to see the surface of the steel at high temperatures. The shade 2 lens is green and you have to get use to the color shift but with a little practice this is not a problem. I would suggest wearing them for all forge work.

When using these glasses I am looking for a surface that has a bright greasy look to it. It should also have a look like it is almost slithering around. This is not liquid but getting close to it. The whole weld area should be the same color with no shadows. If it is an uneven heat turn the bar over in the fire and soak it from all sides. It should be an uniform temperature all the way through.

Another trick to try when starting out is forge a 1/4 inch round bar to a point and bend the point over a 90 degrees. Bring the bar that you want to weld up to temperature with the 1/4 round pointed one beside it. When you think it is right touch the point to the part that you think is at welding temperature in the fore fire. It should stick. If it doesn't stick it is too cold. Soak it longer.

If it sticks ( you should be able to pull it apart) take the weld. Start with simple fold over welds such as handles or even 1/4 by 1 inch flat bars just folded over on itself to learn the temperatures required.

Remember in gas forges this is working right at the top of what they are capable of. A high altitude makes a big difference as well. Above 4000 feet you may need a blower to provide extra air.

Q#2) I have heard that some blacksmith's prefer flux when forge welding while others strictly refrain from using flux because flux introduces contamination to the weld site. If flux is preferred, what are the best flux formulas for forge welding steels, stainless steels and wrought iron?
Flux is a bit of contentious issue. If using no flux your joints and fire have to be as clean as possible. Flux keeps the scale from forming on the bar. Scale does not weld. Some fluxes contain a ground metalic ingredient that lowers the welding temperature and increases the surface area at the joint. All these are good things when joining mild steel. I have used these compounds and they do work well. Trade names that come to mind are EZ-weld, Cherry heat, Antiborax, There are others. The problem comes when you are welding damascus billets as this metallic grains introduce a new layer into the billet and it can muddy the sharp transition between the layers.

20 Mule Team Borax found in the laundry isle has been used for years and works well for all general forge welding. It introduces no metallic contaminate. However there is a downside to using 20 Mule Team Borax. On regular joints it leaves a residue of borax that is very hard to clean off. It can be ground or sand blasted off. The problem with this residue is that it will start to turn white as it is exposed to moisture. So you may have this lovely forge welded piece then it starts to get this frosted appearance at the joints after a couple of years. Not pleasant

Different fluxes for different steels.
I have not forge welded stainless steel, but I understand you require a special flux with a Fluoride component to clean the stainless. Wrought iron should have enough slag in the matrix of the bar that you don't need flux but Borax wouldn't hurt.

I hope this helps
David Robertson
Artist Blacksmith

Wednesday, December 7, 2011

Blacksmith Protective Eyewear Questions

Protective Eyewear Questions

1. Can you comment on fit for people who normally wear glasses - i.e. isn't it necessary to get safety glasses that fit over the regular eyeglasses. I've ruined two different pair of regular glasses because I thought that if I got lenses comprised of 'safety' rated material, e.g. polycarbonate that would work. Well, it might work for safety features, but after a short while I had so many small pieces of metal shavings and welding rod flux imbedded in them, the visibility through them was degraded. To replace these is quite expensive.

2. Why is the tint necessary if the eyewaer has UV protection?

Hi Doug
1) Prescription glasses are a problem. Although if the safety lenses protected your eyes from the metal shards and flux yes they did their job. This is a personal fit thing and yes best option is glasses that cover completely your regular glasses.

2) The forge like a cutting torch puts out UV and Infrared. Most glasses are well protected for the UV but very few protect for the infrared spectrum. The chemistry of the additives in the lens can filter out the infrared. Various tints help you see the metal better by filtering out different spectrums of visible light. The didymium ones I use filter out the sodium flare which is the bright yellow light from the forge.

I recommend shade 2 welding lenses such as Uvex Infradura shade 2 (shade 3 which is more common is pretty dark for shopwork as I start to trip over things). You may also find clip ons available that would protect both you and your prescription glasses but you may have to dig a bit for those. I use a pair similar to the above glasses for forge welding and find them much cooler on the eyes Than the rose didymium that are my regular forging glasses. The infradura filters 85% of the infrared and about 99% of the UV

Also has a more extensive line of specific high temperature lenses. Look for metal working.

I hope this helps.
David Robertson
Artist Blacksmith

Saturday, October 15, 2011

Tips For Forge Welding Above 4000 Feet

Forge Welding at Higher Altitude

By the way I am at 4000 ft. I am told that it is very hard to weld with a propane forge. Is there something you can share with me on what I can use or do before I start to try this????

Most of the trouble with higher elevations is the thin air. You just need more air to compensate for the fuel required to get enough heat for the forge weld. Some people are successful with an atmospheric forge forge welding at 4000 feet. Above that it seems that they need to add a blower to increase the air (oxygen / fuel ratio) . I would try just normally but run your forge hot as possible. Higher pressure. This depends on what type of forge you have.

For forge welding here I use 20 to 25 psi although I am not very high. This does depend on your particular forge though.

If you find you do not get the temperatures required (lemon yellow at least) then you will probably have to look at adding a blower to the system, if your forge doesn't already have one.

The other thing is to put a piece of scrap plate steel down (1/8 th is fine) to cover your forge bottom to catch any drips of flux as it will eat into the ceramic fire brick or the insulation. I use 20 Mule Team Borax and that works fine for me. If you buy "Cherry Heat" or "Anti-Borax" or "EZ Weld" or other trade name flux from either Centaur forge or Pieh tool company or Blacksmith Depot (addresses in the resource section on the website, members area) this type of flux will help lower the temperature for mild steel.

I hope this helps.
David Robertson
Artist Blacksmith

Tuesday, September 27, 2011

How to use Thermal Cycling in Heat Treating a Knife

Thermal Cycling Steps for a Hand Forged Knife

I have a knife that needs to be hardened and tempered. But I read your thermal cycling article and thought that this would be a time to test it. My question is, is when you thermal cycle the steel is that all that needs done or if the knife needs to be tempered after the thermal cycling process? Is all I need to do for the knife is the thermal cycling process that you describe on your website? could you give me instructions for heat treating a knife and axe using the thermal cycling process?

The thermal cycling process is part of the annealing process. So this means it is done before hardening and tempering.
The thermal cycling process changes depending for what type of steel that you used for the knife. Below are the steps for 5160.

The steps
  1. Bring to a bright orange, allow to air cool on an insulating surface such as fire brick or kaowool or vermiculite. This is important for knives so that they don't warp in the cooling process.
  2. Bring to medium orange, the cool as above.
  3. Bring to bright red and slow cool covered in vermiculate, kaowool etc. You may want to heat a bar and leave under it for added thermal mass. Allow to cool over night or until room temperature
  4. After cool it is annealled and ready for the hardening process. Now at this point I do my primary grinding. Shaping the knife but not putting an edge on. I do this after hardening and tempering.
  5. Hardening - depending on the steel and the quench media require air, oil, water etc.
    I heat the knife to an even medium red temperature and check to see if it is non magnetic. If not I will go a bit hotter. If it is non magnetic I will test until the magnet just pulls, then quench completely in the quench solution. At this point the whole blade will be quite hard and brittle. Don't drop it!
  6. Next is the first tempering. I place in a small oven at 425 degrees F and bake it for 1 hour. Best if you have a digital thermometer to check this temperature accurately.
  7. Last step of the tempering process. After the hour in the oven the knife will be evenly tempered to edge hardness all the way through the blade. The best blades have a softer back. So I now take a shallow pan of water (about 1/2 an inch deep) and place the edge down and heat the back of the blade with a torch and you should see the colors move to the edge but stop at the water level. Blue on the back and dark straw on the edge.
  8. Last step. Final grinding and polishing always keeping the blade cool so that you don't mess up the temper already acheived. I usually do one or two passes on the sander then dip in water.
I hope this helps.
David Robertson
Ontario Artist Blacksmith

Thursday, September 15, 2011

How To Identify Different Steel Types For The Blacksmith Shop?

How To Identify Different Steel Types in The Blacksmith Shop?

Your website and newsletters are very interesting to me a person learning the art of blacksmithing.

On the issue of topics you could cover in your newsletters what about workshop techniques for identifying steel types!

Thanks for the idea of identifying steel types.
This is known as the spark test. Many of the blacksmith books cover it in detail but it would be a good idea to cover it in news letter. I will add it to the list. I am a little concerned that my video camera would not pick up the true nature of the sparks. I will have to try it and see what quality of image I get.

Essentially as there is an increase in carbon content the complexity of the explosion of the sparks increases. When different alloys are added the amount, color and length of the sparks change. Use a set of known examples to test an unknown to. This will get you pretty close in determining an unknown steel.

A good reference book that I use often is The New Edge of The Anvil by Jack Andrews (See picture)
It has a good section on using the spark test to identify different steels as well as a number of basic techniques and good background reference information. Check it out if you get the chance.

Thanks again.
David Robertson
Artist Blacksmith

Tuesday, August 16, 2011

Damacus Etching Solutions

What Acid Solutions to use for Etching My Damascus Steel?

I have just finally received my fieldsmithy and anvil and can really start out with my own projects. I wish to focus on blades, from knives to swords, and especially patternwelded. Now I have found a lot of information on patternwelding, but have to practice on it ofcourse. But I can't find anything clear about the acid used for etching to get the pattern out.

I am planning to use iron plates and carbon steel stacked and welded together for the patternweld, and after a lot of research I have found out that on basis of the material used the etching solution is different. So basically my big question would be, what would I use for the iron+carbon steel stack, and what would I need for low carbon + medium/high carbon steel stack when it comes to etching.

There are many etching solutions and all will work to a certain degree.
I have used
Sulfuric acid (battery acid)
Nitric acid
Ferric Chloride

Sulfuric I have been using lately as it is easy to get and quite cost effective. Find a local automotive supplier to get it in bulk.
Nitric has a very aggressive bite and you may only leave the piece in for a few minutes.
Ferric Chloride has a slow etch but easy to control.
Vinegar is almost a discoloration although by heating it you will get a bit of an etch.

With all Acids take proper precautions.
Face Shield
Rubber Apron and Gloves
Neutralizing Agent
Eye Wash
Fresh Water for Rinsing or Flushing
Proper disposal of used Acid solution

Some of the acids can be mixed to achieve different looks. You should experiment to develop your own recipes.
Remember to always ad acid to water for diluting not the other way around.

This book has some useful information on etching for pattern development

Here is another link to Other Useful books With Etching Info
I hope this helps.

David Robertson
Artist Blacksmith

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Tuesday, June 28, 2011

Blacksmith-When To Remove Scale From Work Piece?

What is the best time to remove excess scale from your blacksmithing work?

Is there an advantage to descaling a hot work piece with a wire brush as opposed to just giving the hot work piece a couple of light raps with the hammer thus saving valuable heat? Is hammering the work piece on the anvil that has loose pieces of scale on it detrimental to the work piece?

Sweeping The Anvil Between Heats With Your Glove

You should get into the habit of sweeping your anvil surface between each heat so you are always working on a clean surface. The scale left on the anvil will pit the the bottom of the bar. This is most noticeable on the back of thing pieces of steel such as leaves. It creates a coarse rough texture.

Wire Brushing Hot
A bit different. There are times that you want to quickly wire brush while your bar is hot. Eg. of this would be last couple of finishing heats on things that require an optimum surface such as knives.
The scale comes off well until about bright red then it sticks to the steel.

In general I forge with out wire brushing but with sweeping the anvil between each heat.
If I take a finishing heat I may give it a good wire brushing from dull orange down to black heat to remove the loose scale. Once cold I will use a wire wheel on a grinder or wire cup on an angle grinder to further clean the steel.

I hope this helps.
David RobertsonLink
Ontario Artist Blacksmith

Monday, May 16, 2011

Steel Designations and Bellows Back Flash

How to prevent bellows Flash back and basis of steel designation.

Hello David

Thank you very much for the valuable information you have provided me so far, I am always looking forward to your next subject

I do have a few questions, although I heard that when using bellows, the bellows may be destroyed due to gases forming on the inside If the bellows were hung higher than the forge, would this prevent this from happening?

2. what would be the best metal to use, cold rolled steel or hot rolled steel and what is the meaning of 1030 or other number associated to the steel?

Thank you for helping the newbie’s like me, it is much appreciated

Good questions.
The bellows should be set up with a check valve inside so it can not draw gasses back in from the forge. The check valve originally was just a flap of leather on the exhaust that closes when the bellows is opened. This means all the air is sucked in through the inlet ports and none of the fuel gases from the fire which could be exciting indeed. Hanging the bellows higher than the forge will have little effect in preventing the problem.

Metal to use
The number designation refers to the type of steel and its alloy content.
The 1000 series means that it is just iron and carbon in the mix.
1018 or 1020 are both used for cold rolled and hot rolled. It is the same type of steel but as the name implies one is worked cold and the other hot. Cold rolled has tighter tollerances in size and requires more energy to make and costs a lot more. Hot rolled has more variation in sizing and has less stress put into the steel so it will bend easier. Once either are put into the forge they will work the same as there is no difference in the carbon content.

So back to the number designation. 1020 means a simple iron carbon mix with 20 points of carbon or .2% carbon. 1060 would have 60 points of carbon or .6% carbon.

5160 which is car or truck leaf or coil spring material is a different series. The 5000 series contains chrome. So 5160 has about 1% chrome and .6% carbon. Other series will have different major alloying components. Google knife making, and alloy steels, and metallurgy for information on each different steel series and their uses and properties.

Mostly for blacksmithing I will use hot rolled for general art work or 5160 if I am making cutting tools or hand punches. Other specific tools and punches I will use better suited materials such as S7 or H13 (yes there are letter designations as well).

Hope this helps
David Robertson
Ontario Artist Blacksmith

Tuesday, March 8, 2011

How To Make Different Damascus Patterns in Pattern Welding

Damascus Steel Patterns

Sorry to bother you so late at night (over here anyway)
But I was wondering what patterns you can pattern weld I have seen your ladder pattern and other patterns on the internet and was wondering if you could give me a few tips.
That you for your time.

There are hundreds of patterns and variations to work on.
Most are based on layering steel, then either modifying the surface such as the ladder pattern (cutting material away) then flattening and grinding to expose the pattern.
flat layers that are twisted, then shaped, and ground to expose the pattern.
Both of these techniques can become very complicated depending on the layer count and the manipulation.
There is a third technique
Called Mosaic Damascus
This can be done with powdered metal or machined "pixels" put together to create a "picture" in the steel. It is a bit of a different process using a hydraulic press for the fusion weld to maintain the structure of the picture.

The best thing to do is get 2 colors of modeling clay and layer them together like a damascus billet and then twist and manipulate them. Then use a knife to cut some of the outside material away to expose the pattern (sames as grinding on the steel). Experiment with this but keep notes as you go so when you find a pattern that you like you can reproduce it in steel. This is a fast low cost way to experiment with these techniques.

A couple of very good books on the subject are
Damascus: Forging Techniques
The Complete Bladesmith: Forging Your Way To Perfection

You may want to check out some the knifemaking forums for some other details.
I hope this helps.

David Robertson
Artist Blacksmith

Thursday, March 3, 2011

Blacksmithing Removing Scale, Tinted Glasses, Upsetting

Blacksmithing How to Remove Scale, Tinted Glasses, Upsetting

I have a few questions for now.
If you use hot rolled steel how do you remove the scale on the parts that is not heated for forging? Do you use a wire wheel, and acid bath or sand the area?
Do you wear special tinted or filtered glasses when you do blacksmithing and have to stare at the fire alot.
I want to flare out a 3/4 square bar so that it will form a pyramid type base. If I heat it should I slam it on to a thick steel plate to flare it out. Is that the best way to do it?

Removing Scale
There are couple of options, they mostly depend on what coating you are putting on it.
Wire wheel for clear coating.
Sandblasting for paint.
Acid etch for galvanizing but this is done at the galvanizer.

Mostly it depends how you want the finished piece to look. Complex shapes may not get completely cleaned of for clear coat and painting.

Tinted glasses
Yes I wear rose dydimium glasses. This is the old filter style originally designed for glass blowers. There are other filters that are better recommended for blacksmithing such as AUR-99 from I have not used this lens so can't really comment on it. The exposure to UV and IR are generally minimal in blacksmithing, but it does become important with lots of forge welding as the temperatures are so much higher.

Upsetting 3/4 inch square bar
Depends on the length. short can be done on the anvil or clamped in the vise and a light hammer used.
Long bar yes heavy steel plate on the floor and it is sort of bounced on it.
It must be at yellow heat. You should also taper the edges (basically knocking the corners off the end of the bar) this lets the force go deeper into the center of the bar instead of being dispersed at the end. Upsettting is tricky to do well. Practice first and easier to do on a larger bar than a smaller one.

I hope this helps
David Robertson
Ontario Artist Blacksmith

Saturday, January 29, 2011

When Can You Call Yourself a Blacksmith?

What Does Define a Blacksmith?

I know you probably had this question asked of you many times. But at what point in metal working are you really allowed to call your self a blacksmith? I mean going out and pounding on a few pieces of metal isn't really blacksmithing. What does define a blacksmith?

This is actually a tricky question.

In North America there is no governing body of blacksmiths, so legally
anyone who works with steel could call themselves a blacksmith. This
causes a whole lot of confusion with the general public. A cold
fabricator calls themselves a blacksmith but charges 30% of what a
person who works with hammer and anvil and shapes the hot steel. The
fabricator only has 30% of the time into the project.

There are measurable fundamental skills associated with blacksmithing.
Do all of these have to be mastered for a person to call themselves a

There are tools required for the work. Can a person call themselves a
blacksmith if they don't have the tools required to do the job?

Should a person call themselves a blacksmith until they are making an income from the smithing? Should it be a full time income?

Is it more esoteric? Such as when a person has to smith. When they are
drawn to it as a passion. Some would say "When it is their blood". A
number of smiths have told me of this calling back to the anvil when you
have been away from it for a while.

My Opinion

A person can call themselves a blacksmith when they have a good ability with the basic techniques with hot steel.

Drawing out, pointing, shouldering, flattening, punching, twisting,
square corners, hot cutting, splitting, curve generation, tool making,
upsetting, forge welding. They also have the facilities to do the work.
This may be as simple as a back yard forge, anvil and hammer.

It really is a gray area and each person has to make their own decision
when they can call themselves a blacksmith. There is no-one to call them
on it ( In North America) except their customers, which often are not
well educated in the difference between hot work and cold work.

David Robertson
Artist Blacksmith