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Author Topic: What did you do in the Holidays? I cast a "modern" Bronze Age Sword  (Read 1943 times)

jmone

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In another thread, JimH asked what we did in the break. 

I've done a bit of metal casting over the years with Tin, Zinc, Aluminium, Silver, and Copper Alloys (Bronze, Brass, AlBronze, SiBonze, "Nordic Gold", etc).  I've normally made small items like Aluminium Plaques, Copper Spinning Tops, and Birthday Bars with a coin from the recipients birth year (500g of Cu or NiCu pending if the coin is copper or silver coloured) with an epoxy base.  Event cast some "Ides of March" coins for my Daughters themed birthday party.  All of it took a surprising amount of Trial and Error to get working but once you have the method for each items then you can repeat it .... but it takes me a dozen attempts to get something that works well enough (I've now started keeping a casting diary with all the details as I tend to forget exactly how I did something a few months or a year later.

Anyway, I figured it was time to step up to the "big time" and see if I could make a modern interpretation of the Ewart Park Sword from the height of the Bronze age some 3,500 years ago.  How hard could it be?  So far, I've found a dozen ways of how not to make one! 

My last attempt pictured below consisted of:
- 3D Printed a scan of an Ewart Park in several section on a resin 3D Printer
- Glued and smoothed these parts to a pattern board making sure it was on the centre line between the locating pins of the casing box
- Rammed up the Cope and Drag on the pattern board using homemade Green Sand (with Talc as the parting powder). 
- Melted 2KG of Beryllium Copper Alloy (C17200) for the pour @ 1200c in a gas furnace
- Feed the pattern ever 10cm during the pour (it turns out is is hard to cast a long, thin, and light object and expect the casting to "fill" correctly => 1st Pic (of "copper" coloured)
- Age Harden the Sword (1h@ 320c).  This makes BeCu as hard as many steels => 2nd Pic (now it is a silver black colour)
- 3D print the hilt in ePA-CF (Carbon Fibre reinforced Nylon)
- Cast a button (using my Icon/Logo) for the pommel (50% Silver/Copper) => 3rd Pic
- Grind, Polish, and Epoxy it all together => 4th Pic

I take my hat off to our distant ancestors.  I'd not even make the grade as an apprentice, and this attempt would go back into the melting pot.... but I'm out of time and it was my first complete casting from many tries. 

Some other notes on my "modern" take on a 3,500 year sword and what I'd "tweak" if I was to do another attempt:
- BeCu can be a dangerous material to work with, it is perfectly safe in it's final state and offers the hardest of all the copper alloys rivalling many steels once age hardened.  Much much harder than the Bronze originally used.
- ePA-CF is very tough, has a bit of flex, has a good surface finish, and fits with the "modern" interpretation (plus I'm useless with carving wood)
- The blade of my sword weighs 885g while the "originals" are around 750g ish.  Most of the weight difference is that I filled the tang to be solid instead of semi cut out for ease of casting.  Adding the handle and silver button takes it to 1040g. 
- While I've ground an edge, I've not honed it.... as I still managed to cut myself on the blade!  (my wife did say "If you play with swords, expect to get cut....")
- You can see an issue with a depression across the blade at 5cm from the handle.  This was at a junction in the pattern between two parts.  I'd printed out the slightly thicker handle section but not sanded it to a smooth enough gradient to mate well with the blade sections.  I suspect this caused some turbulence when pouring and it did not completely fill the mould at that point (though it is plenty strong).
- I would make the grip section a few cm longer for a more comfortable grip (they must have had smaller hands back then)

Anyway, it was a lot of fun and the whole project took a couple of weeks (on and off - across many attempts) to get it to this point.

Thanks
Nathan
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JimH

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Re: What did you do in the Holidays? I cast a "modern" Bronze Age Sword
« Reply #1 on: January 08, 2022, 08:03:55 am »

Holy Cow, Batman ! 

I love your wife's quote.
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