Casting Anvils

[A. Humphrys]

I've been a lurker here for a while, but I figured my latest project might just be worth sharing. I hope you all agree.

Just a bit of an introduction. My name is Adam Humphrys, I'm not much of a bladesmith, but I'm hoping to get better. My saving grace is that I'm pretty decent at casting things. I graduated from Virginia Tech this year as a Materials Scientist and Engineer, going on to get a job as a metallurgist for an engineering firm. That said, one of the best parts of my education, about two years of it, was participating in the VT FIRE program. (Foundry Institute for Research and Education) The firm that I work for is very closely tied to the program, and as such I keep in contact with my professor and a number of student whom are still there. Every now and again I get asked to do something cool, or assist with something cool. This project is one of those times.

In one of my recent discussions with my old professor he brought up a research project on forged materials. Specifically a forge weldingproject proposed by another engineering discipline. That's all well and good, only trouble was he didn't have an anvil. Now us being foundry guys, well we think that's something we can take care of. And so the quest to cast an anvil began.

Now, I mentioned I'm not much of a smith. Furthermore, I've always been a bit of a broke smith, so my anvils have always been scrap blocks of steel. As such I know I made a few mistakes in general anvil morphology, but I hope they are forgivable. That out of the way, this is where we started. This little sketch and CAD gave us a general idea of where we were heading, about a 130lb anvil.

So far it’s a more proper anvil than I have ever had. And with a drawing in hand, I moved on to building some patterns. Now there are a number of ways to go about this part, you can basically make patterns out of anything. For me, I choose some nice sheets of MDF. Specifically one sheet of 4'X8'X0.75” and one sheet of 2'X4'X0.5”. I prefer MDF over wood and plastic for only a handful of reasons. The first reason being that I can use it for the pattern, the match plates, and the flasks. The second being the uniformity of the material and its relative ease of shaping with simple tools. First thing I do
is make a pattern of the silhouette of the anvil out of the 0.5” mdf. I make this slightly over sized and use this to draw out duplicates on the other sheets. You can see it laid out below.

The anvil body is made of 4 layers of .75” and 2 layers of 0.5”. When you put the thinner sheets at the center of the stack you end up with a 4” thick body that splits evenly into two 2” thick anvils. This helps me later on when we get to molding this up in sand. Two pairs of front and back feet from 0.75”; sheet finishes up the raw materials. I screwed the body together in two halves with two screws holding both halves together. I didn't attach the feet right away so I could true up the sides on a disk sander smooth out any inconsistencies left by my bandsaw. The pile of anvil pattern parts is below.

Once the sides are trued up I glue the feet together. Now before I put them on the anvil I took them to the disk sander to make a nice smooth transition from the foot back to the main body of the anvil. Once the feet have been contoured they get glued and screwed to the anvil and a few pins to keep everything from wiggling loose later on. (You might be surprised how much abuse a pattern can get in a small research foundry...) A little work with a rasp on the horn and you end up with something that looks like this.

Close enough to be considered an ASO right? Well aside from the woody consistency.. it’s all about potential...

Now never being someone to leave something well enough alone.. I took a bit of creative license and added some artwork while I smoothed and patched some holes. For that I picked up a Fix-it Stick at the local hardware store. It's a two part epoxy clay stick that is filled with steel powder. I'm pretty sure they make a similar product with sawdust instead of steel, but this is what I could find. I mixed the stuff up in really small pinches and worked it into little cuts in the anvil, then I would carve it back to make my designs or to even out patched up holes. When the stuff cures, it cures very hard. It can be scraped and filed, but after it cures it can't be carved so you have about a 10 minute window to get the work done. Below you can see my stencils and what I ended up with. One side is a phoenix of mine, and the other is the program logo. I guess you could call the bird my maker’s mark of sorts...

Now nothing is perfect... but man I sure spent way too much time trying....

And now the gritty part, sand molding. (I have a problem... I know...)

This particular project uses a three or four part mold. It consists of two molds that house the anvil, a third that makes the face and holds the risers called a cheek core, and the fourth is the core for the hardie hole. We left the hardie hole out on our first pour as this first attempt is to make sure we don't have any glaring casting issues. All of these parts are made with a no-bake sand system. No-bake is basically sand mixed with epoxy. You dump it in, pack it in, let it set, pull the pattern, let it cure, then pour. It’s a pretty easy process to get used to, and much easier to move around than greensand molds. Below is a picture of the flask for the cheek core. The two tubes in the center are insulated riser tubes not that different than a compressed fiberwool. Below that is the first half of the anvil mold. Same type of flask as the cheek core, except instead of the riser sleeves we put half of the anvil pattern at the bottom with the face pressed up against one wall of the flask. In the second picture you can see our sand mixer. The bright yellow nozzle is where the mixed sand comes out and the table that the mold is sitting on is a vibratory table. This along with a bit of elbow grease gets the sand packed and settled in quite nicely, and provides a very nice surface finish and high detail.

 

When the above mold has set, its striped from the flask, and the pattern is removed. The second half of the anvil pattern is screwed back on to the first and the pattern is replaced into the mold. The mold is placed back into the flask with the pattern facing up. New walls are put back on the flask that are double the height of the ones above (12” vs 6”) Some notches are cut into the first mold (for realigning later on) and talc is dusted onto the mold. Then the second half of the mold is made directly on top of the first. This is the easiest way for us to get the best fit and alignment on our molds. You can see them with the patterns removed after molding. If you look there are some fins that stick out of one mold that line up with the notches in the other half. Also notice the cuts on the outside of the mold.. These things are heavy and every bit helps when trying to get fingers underneath. The second photo is of the two together.

 

Now I have to confess... I was not present when the students poured this mold.. So I'm missing all the great action shots. That being said, we will pour again and I'll try to do better next time.

Below is how the complete mold looks when it's fully assembled. If you notice the dark areas, that is burning/burnt epoxy binder. Stuff stinks like crazy, but when our dust collection is on you can barely smell a wif of the stuff. I digress. You can see the two larger molds at the bottom, these are clamped together with angle iron and all thread. On top is the cheek core weighed down by ingots, and on top of that is a pour basin with a filter held on by core paste (glue.) This picture was taken about 24 hours after the pour. What photos don't show is that this puppy is still smoking.

 

For the test pour the anvil was cast in ductile iron. Our ductile iron pours are limited to 125lbs due to the nature of magnesium reactions and the size of our crucibles. That said we weighed our pattern and estimated a finished casting weight in iron of 116lbs. Close but we gave it ago.

Now for the Christmas morning sequence...

Aaaaaannnndddd.......

Now as I said before... nothing is perfect, but I tried. And for a test, we did alright. Sadly, the casting ran short. There is exactly 116lbs of iron in that casting, apparently the remaining 9lbs that were melted got lost in slag. As such there was not enough to fill the risers and create enough pressure to fill the corners of the face. You can see some minor shrink where the risers would have been. Live and learn... and then pour them in A2.

Our plan now is to make another mold, and pour it in A2. Our furnace can melt up to 300lbs of iron or steel, and when we don't have to magnesium treat it for ductile iron, we can pour it all straight from the furnace. That is just what we will do. At the moment we are at a bit of a pause in the project. We're waiting on ferrochrome and ferromoly to make our batch of A2. We might have to substitute tungsten for vanadium, but that shouldn't affect the behavior of A2 too much. A couple of other mistakes reared their heads so far, and will be addressed before the next pour.

As I mentioned before... I will do my best to get you guys some action shots when we move to steel... casting steel gets downright exciting...

I hope you all enjoyed this.. and more to come down the road (maybe days.. or weeks)

 

Adam

[Clifford Brewer]

Cool beans I'll be waiting to see the steel casting !!

[jake pogrebinsky]

Neat project!

 

U.S.has excelled at casting envils.Fisher,on the higher end,Vulcans,a few others.

(Pooh-poohed by the prissy,they're actually functional and reliable as a rock;i've used nothing but in all my forging,and could wish for nothing better,they're the most noble tools,capable of reaching rebound values in the 90-ies percentile).

 

Unfortunately i'm not aware of any details about the process,other than a rumour about the proprietary technique used by Fisher of casting onto a cold or pre-heated steel face-plate incerted into the mold.Judging by the evidence of where you can see the parting lines on a cast anvil,i've always pictured the mold as something along of what you used.(Too bad that you didn't splash some of that A2 into the mold first!

(BTW,is A2 air-hardening,and is that why you guys want to use it?Sounds neat,anyway!).

The hollow from the shrinkage of the casting helps the base to sit level on the stump.

 

The crystalline structure that a solid-steel anvil will have will be cool,wonder if it enhances it's qualities as an energy-reflecting device!

 

Generally,American and British anvils mostly contacted the anvil-stump with their entire base(The Germans liked their anvil's base REALLY wide).

The feet that you used in that model is very much like the French anvils,that often were standing up on their feet(which together with their twin horns made them particularly creature-like:)

 

Bravo,it sure is one cool project!

 

 

 

Cast

[B. Norris]

Gosh darn it. I never seem to have the right kind of people for friends! I sure hope this guy appreciates what you are doing for him.

 

I once talked to a bloke at a fair in Sioux City, IA who worked for a foundry and they would let the guys have some fun off hours. He was saying they would gather up scrap railroad rail and pour some anvils once in awhile. Seemed like it would be a decent alloy for the purpose,. Other, commercial, cast anvils have been done in 6150, it is common, not overly expensive, gets pretty darn hard and is awesomely tough. A2 seems like an expensive steel to use with no real advantage to the extra layout. I doubt that it will air-harden in anvil sized masses but, you never know until you try. I imagine that you could have quite a demand for anvils you cast (if you wanted to) especially if you are able to make them up to the customers designs.

 

~Bruce~

[Ben Noffsinger]

Very cool! I love the added bird(phoenix?) Please do post your progress!

[Ethan P.]

Gosh darn it! I originally wanted to be a materials engineer, but my college didn't offer it, so I went with chemical instead.

Materials science is still my jam, though, so it's nice to see what it would have been like!

Looking forward to hearing more from you,

 

-Ethan Perry

[Alan Longmire]

COOL!

 

How are you going to do the heat treatment? With A2 I bet simple flame hardening would do fine.

 

Most cast steel anvils in the past (not cast iron/steel faced like Fishers and Vulcans) were made from an alloy similar to W2. Columbians come to mind there. Modern cast steel anvils range from 4140 (Nimba) to 8620 (Rathole) to H13 (Jymm Hoffman) to ductile iron (TFS).

 

Your design is pretty nifty, but if I could do one of my own I'd make the base flat or with a slight recess underneath, just from personal preference. Yours has plenty of mass where it is needed, which is great. The horn could be a little more rounded on top, but that can easily be done during the post-casting finish grinding.

 

How are you going to handle the hardy hole? Cored casting or drilled and broached afterwards?

 

I applaud the project! And you're only two hours north of me...

[Richard Furrer]

With modern induction heat treating being so easy to get access to I suggest using whatever casts well.

A2 would not be my first choice, but it is not my last either.

 

Since you can make any shape you wish then I suggest playing a bit fast and loose with design. Why make what is already out there? Do something more sculptural.

 

Ric

[Noah M Legel]

That is awesome! I would have gone with a flat base, rather than an arched one, but it looks great, and the phoenix on the side is a nice touch. Man, I need better friends!

[Dave Stephens]

Very cool!

 

Any plans to sell custom anvils?

 

If so, put me on the list.

 

Dave

[A. Humphrys]

Thanks for the kind words gentlemen.

 

As I said before, Anvil morphology was not my strong suit.. it didn't even occur to me that I had cut the base in too deep until I went back and looked at my drawings after casting the sample. The bright side on that is it helps with the directional solidification... which lets me get away with our riser configuration. I think I can make it work though. If I do this again, it will be much smaller of an arc if at all and yeah, I think I would go well beyond the typical anvil.

 

The picture below is the hot side of the foundry lab. The cold side contains all the sand equipment, investment equipment, finishing, small heat treating ovens, and the metallurgy lab. The hot side is where the really hot stuff takes place. You can see some of it in the picture. We're gathered around the 300lb tilt furnace for a ductile pour, you can see the treating crucible under the torch off to the left. Behind me (the guy on the left) is the lift swing furnace, this takes conventional crucibles and is what we do all our copper base and some aluminum out of. Both of these furnaces are induction and the power unit is the big blue box on the right. Between me and the next guy you can see our normal aluminum furnace. Where the crucible is heating up is our pouring area, the cream colored structure above it is a dust collection system. That system is also attached to every piece of equipment in the building and keeps the air extremely clean. And the little yellow control pendulum is for the overhead crane. Out of picture, behind the photographer is the de-waxing oven for investment casting. Its a monstrous natural gas furnace with a 4ft cube chamber.

 

 

We chose A2 for a number of reasons, and while it may not be the best, it has some things going for it. On our side of things A2 isn't all that expensive, that being said we're looking at an modified A2 with higher tungsten and lower vanadium to make better use of what we have. For us, about 900lbs of A2 runs about $150 plus scrap prices. Ferromolly is what costs, and other alloys take considerably more than A2. Second, A2 is air hardening. While we have everything you could think of to make something hot, what we don't have is quench tanks or a good method of handling super hot castings. We have plenty of fans though, and I think I will end up casting a very large aluminum heat sink to quench the face. I think that it is far safer and more feasible for us to make A2 work than it is for us to venture into untested territory on the quenching side of things... our de-waxing furnace is more than capable of reaching austintizing temperatures and should suffice for both annealing and hardening A2 albeit is a bit wasteful.

 

Alan, the horn is a bit more of a block than it should have been. You can see in the picture of the mating mold halves that the very top of the mold broke out. This happened when we stripped the pattern from the mold, and while its a bummer to have to grind it all back, it looks worse than it is. The rest of the horn came out very well with the exception of one spot on the opposite side where an extra screw had to be added and left a nub.

 

The hardie will be cast in place, and possibly the pitchel as well. I'll use a sand core dipped in core wash which should cut down on metal penetration into the cores. That will save us the headache of trying to bore and broach. My goal is that the run in A2 will only need the face and horn ground before it is ready for heat treatment and use.

 

I hope to have more for you all before too long.. though I have the feeling it will be at least 2 weeks before our supplies arrive. We're completely at the mercy of our alloying elements being delivered.. That said I do have a line on a couple hundred lbs of 8620 that apparently is good for anvils. I would have to outsource the heat treatment though.

 

Dave, At this time, no... but I am trying... I want anvils too....

 

[B. Norris]

Just my opinion - an 8620 anvil would be better than nothing but, I'd rather have something higher in carbon and hardened. From what I'm seeing this alloy is intended to be tough and to have any wear surfaces hardened by carburising for higher hardness. Are you capable of case hardening the surface of an anvil made from this alloy? Even if case hardened, it would be a very thin layer. I would think that with all the work involved, choosing a more suitable alloy would be the way to go.

 

If you can make up coils for your induction unit, an A2 anvil could be easily hardened. Just make up a flat, pancake, coil and heat the face of the anvil. If you search this forum, there is some information about specialty induction coils. The mass of the rest of the anvil as a heat sink would probably be sufficient to cause it to harden. Add in a massive, aluminum, heat sink and a bunch of fans and it is pretty much a sure thing.

 

Other alloys could be hardened in the same way but, you would need to come up with a way to quench them for hardening. However, it would be easier because, with the induction coil, you would be able to heat just the face and significantly reduce the volume of quenchant needed. I suspect that you could accomplish hardening with a garden hose and a nozzle capable of producing a fine enough spray. The trick would be in getting the volume of water/air in the spray just right for the particular alloy you were using. Handling such a large mass of metal, in this case, could be as simple as putting the anvil on a hand truck, heating the face with the induction unit, then rolling it outside and spraying it down.

 

~Bruce~

[John Page]

Wicked project! I wish I had the capabilities to do something like this. I'm excited to hear how it performs.

 

John

[A. Humphrys]

John, I'd just about kill for a shop like this of my own. That said I couldn't afford to run it for more than a month. I'm grateful for every chance to work with VT's facilities now that I'm an alum.

 

Bruce, 8620 makes some great base material for other steel alloys. But in the end you might be correct. I don't have my technical books in front of me at the moment, but i doubt that 8620 quenches too hard. I seem to remember it has some cold work potential though.. But don't hold me to any of that.

 

As for induction hardening... I'm going to leave that to the experts.. and the guys with the cool induction forges. And here's the reason why.. a high power induction forge runs at 25 kVA which is equal to 20kW. The induction controller pictured above runs at 125kW. The leads that run to the coils are braided copper about 1 inch in diameter and you must be a certified electrician to even open the case. In short, it's far too much power for me to mess with. That said, there is plenty of power to get the job done.

 

The alloying supplies are in route. We should be back at it some time next week. I will try to get more detailed photos of the molding process and the pouring process.

[Richard Furrer]

125KW inductortherm unit with flow through cooling and tilt furnace...most likely running 3,000Hz?

looks like a $105,000 system there....less the discount to educational institutions.

 

Good thing to have access to.

 

I prefer Pillar or Tocco/Ajax, but....you use what you have.

 

I'm sure you will work this out and make good tools.

 

 

Ric

[Jerrod Miller]

I have been wanting to make an anvil for a while now so I have been searching the forum for any tips I can find. I would never really even think of making an anvil like I am planning on (250-275 pounds), except I work in a steel foundry. Then I find this and I can't help but consider it perfect timing!

 

Pretty much everything I see out there for hardening an anvil is all about just hardening the face, which is understandable as it is enough of a challenge for the do-it-yourselfer. I would actually have an easier time getting my anvil through hardened with other parts we make. We have a quench tank that is 10,000 gallons with heavy agitation from 2 big props. Would it be bad for an anvil to be through hardened? I image that there is some reason that the older manufacturers went to all the trouble to forge weld a steel face/top to a wrought base. Anybody know why?

 

I am currently planning on making the anvil out of 8630. Well, our casting version of it; you generally do not want the same composition for casting as you do for forging. We also make a 4330 type, but it is more expensive. Next week when I am back at work I will dig through the records to find what alloy we make frequently that gets hardest and probably go for that one, as we don't really make anything above a 0.30 carbon. Any thoughts there?

 

Thanks for any input anyone may have!

[Robert Dark]

Is that an Inductotherm furnace? My Stepson installs them for EMSCO, a part of Inductotherm. Cool stuff. Can't wait to see your NEXT finished product.

 

Robert

[Alan Longmire]

The ONLY reasons the old makers used a wrought iron body with a steel face is that a.) they couldn't cast steel reliably in anvil-shaped sections, and b.) steel was so much more expensive than wrought it was traditional to only steel the part you needed to be hard. Even Fishers were made the way they were (cast iron body/steel face in the mold) is because of the technical issues with casting steel in that time. Most anvils made since the 1920s are solid cast steel, it's no new thing.

 

Now then: as for why not to through-harden the whole thing, I can't think of a really good reason off-hand. The old hard face /soft body is good for withstanding stress, the same reason we still use case hardening on some parts.

 

Now for my own question: Is 8630 deep-hardening enough that it would not produce a case/core construction on quenching anyway? How hard does it get, anyway? For an anvil face you should be aiming at somewhere in the Rc 50-55 range, not lower than Rc45 so it won't dent, and not higher than Rc55 so it won't chip or spall on the edges with a missed blow.

 

I do know that larger cast anvils have trouble getting the center of the face fully hard. My 100Kg (220lb) Refflinghaus is a cast steel anvil, and it is noticeable softer in the middle of the face than on the edges.

 

At any rate, go for it! Who knows, your company could become a new anvil supplier if it works out well.

[Jerrod Miller]

In the foundry world, 1920s IS a new thing! We (as an industry) use a lot of old equipment, WWII surplus being extremely common for many of the major parts of a foundry (furnaces, ladles. etc.), let alone procedures.

 

8630 has pretty good through hardness (the chemistry we use at least, but I will check some of the samples we have to see how good it is in the test blocks in 2"x2" vs. the 5"x5" sections (a couple of our standard test blocks). I have some quenched and tempered 8630 in my office I can get cut up so I can polish and etch it to see it on the microscope. That will give a good idea of martensitic transformation, regardless of temper (and therefore hardness properties). That was also another thought of mine: Would it be bad if the center was soft? Sounds like it probably isn't a bad thing. I would expect all faces to be pretty equally hardened from a quench, though corners would get a bit better due to the greater surface area to volume ratio for cooling there.

 

Also, I plan on casting my anvil in a horizontal configuration. Easier pattern than vertical to still get all the casting features I want. I have to have draft on the feet and face, but nothing a little time on the surface grinder won't fix. Still easier than cleaning the riser contact off the face.

 

Adam - speaking of riser contacts on the face I highly recommend you flatten the base of your pattern and flip it over, putting the risers on the feet and the face in the drag. This will give you a cleaner face surface, make it less critical for riser removal flatness, make short pours less of an issue (who cares about a little shrink in the bottom?), and eliminates under-riser segregation in the critical area of your casting - the face. The latter being even more important as you go to higher alloy content. That was my reasoning for doing it horizontal anyways. Also, casting simulation showed a sound casting with only one riser on the side.

[Jerrod Miller]

OK, so I haven't been too thrilled with the 8630 hardnesses I have been seeing, but I recently stumbled upon an alloy we make with about 0.50 carbon (I knew about it before, but we make it much more often than I thought, so it is possible to work an anvil into the mix too). Time to reseach how that one looks through heat treat. In other news, I thought I would add a couple images showing the proposed anvil design I have been kicking around. It currently is estimated at about 250 pounds. Fist time posting images to the forum; hope this works. Any design ideas would be much appreciated.

 

[Clifford Brewer]

Jerrod, looks like a beefy design and just a thought, on the back end of it maybe a straight line from the bottom to the top rather than a curve to give a little more support under the hardy hole

(sorta Peddinghaus style) I like the central mass of this thing.

OH Yeah I would GLADLY volunteer to do an extensive use/test study on one of these

for either or both of you guys......

Edited March 8, 2013 by Clifford Brewer

[Alan Longmire]

I'll second Clifford on the straight line under the heel. I know, it looks cooler with the curve, but mass under the hardy hole is handy. Also, six inches is a WIDE face for my taste, but that's no big deal. You overcome that with the square horn end. Speaking of which, you might want to make the square horn longer with a narrower heel. My 220 lb double-horn is 1.5" wide at the very heel, and sometimes that's too much for what I want to do with it. Again, no big deal, I just stick a 1" wide block in the hardy hole.

 

I do like having the step, I miss that on mine. Comes in really handy for backing up work.

 

While you're at it, go crazy with the detail you can get on the non-working surfaces and make it a sculpture! Church windows, upsetting blocks, maybe a slant-side section, or even a side horn. Look at Rathole Forge, Refflinghaus, Euroanvil, and Josh Greenwood's antique anvil gallery for inspiration. Oh, and the anvil gallery at Anvilfire.com, Jock has a lot of nifty pictures of old anvils. Get creative, may as well have fun! You are, after all, creating a tool that will last hundreds of years. I know, easy for me to say, I'm not making the patterns...

[Jerrod Miller]

I was liking that the straight line under the heel would be a good idea because that would make the pattern easier. Then there was that whole last paragraph. I am nowhere near a good enough wood-worker to go crazy. I do plan on making something that is going to last a long time, so I would hate to put something ugly on it.

 

Thanks for all the key words to use in a Google image search. I will look for a few more style options. What is bad about such a wide face?

[Alan Longmire]

Nothing bad as such with a wide face, it's just not what I'm used to. Most of what I do is tomahawks and small axes, where it's often an advantage to hang it over the far edge of the anvil. A wider anvil just makes it harder to do that and still have good tong purchase.

 

If I only did blades and ornamental work it would not be an issue at all. I'm just used to a 3.5 to 4.5 inch wide face, that's all. I have done some work on 8x12" die blocks, and I just get lost with that much working surface.

 

This is for you, so it's yours to design as you see fit.

[VaughnT]

Absolutely fascinating to watch this stuff!

 

Jerrod, I would definitely recommend at straighter line under the heel of that anvil. The whole thing has a blocky appearance, except for that one curve, and having more meat under the heel will make it stronger and ring less.

 

As for decorative features, I'm all for it. There are ways to "cheat" if you aren't good at woodworking, or you could find a local woodworker to assist you. There has to be a bunch of locals that would love to pitch in on a project like that! Church windows. Slant sides. Maybe some engraving.....

 

Sooo wish I had a foundry handy!