Casting/Copying question

Daniel Koster

Daniel Koster

www.kosterknives.com
Knifemaker / Craftsman / Service Provider
Joined
Oct 18, 2001
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I have a large, complex knife that I want to send across the USA/CAN border to have the sheath made (customer's request). Already, I've put in over $1000 worth of work/materials into it...so I'm not too excited about customs, etc...

I'm wondering if there is a way to make an exact copy of the knife...using some kind of casting method.

In my simple mind, I see making a mold out of plaster, and then pouring in some kind of plastic, rubber, etc.

But I really have no clue. :rolleyes:


Got any suggestions?
 
How about a folding box (like a jewlery box that has a hinge in the middle), fill both sides with fine sand mixed with light oil to make a kinda green sand (i think that is what it is called), pack them fairly well in the open box way, then put the entire knife in it, close the lid tightly, let set a few minutes, then open it up, take out the knife, close it back together and get some clear casting resin from a hobby store, mix and pour in the empty space (hopefully thru a spru hole already precut into the box, like at the end of the handle side).
 
Send the knife to the buyer and let HIM send it....his knife , his risk.
 
Terry - I like your idea. I went to the local craft store to see what casting stuff they had. The only downfall to the box idea is that the blade is 14 inches and curved....:( Might be too much box for me...:p

What kind of sand and oil do you use?

I found a cast resin that sets in 5 minutes or so....looks like the way to go - immediate results. I don't want to use plaster if I can avoid it - the box showed the mold made of rubber....but what kind of rubber to use?
 
I havent actually done much casting, but read about it a little. I think any fine sand and light oil should work for your purpose, and even a cardboard box would probably work.
I read about it here: http://www.backyardmetalcasting.com/
and i remember Bruce Evans discussing some casting before, a horses head i think.
 
The sand is casting sand,or mold sand, a nearby foundry should have plenty of it,or get it from a jewelers supply.Use any firm frame.Fill the bottom frame with an inch or two of the sand and pack firm.Set the knife on it,flat, and tap it down till it is exactly halfway in the sand.Sprinkle separating powder on the surface (talc will work) and place the upper frame on.Fill it with 1 inch of sand and ram down till hard.Place a piece of 1/2" mesh hardware cloth (Mesh wire) on the sand and add another inch of sand.Pack hard.( the bottom can be done the same way,sand-wire-sand) Carefully lift the top mold off the bottom,remove your knife,make a sprue hole to the handle end,reassemble the frames,and pour with molten aluminum (the plastic resin should work too - maybe).The casting will need to be cleaned up a bit,but should be a good copy of the original.I would wrap the knife in a layer or two (or more) of electrical tape to make the mold a tad larger (to allow for the cleanup) and to protect the finish.If you make it ,say .100" oversize filing to a perfect copy should be a breeze.
Sand casting can be read up on in a lot of metal working books,and online.
You could make a two piece plaster mold basicly the same way.In plaster use vasalene for the separator between the top and bottom (after the bottom has hardened,grease the wrapped knife first,too).
 
You can make a rubber mold by getting the supplies at ther hobby store..I picked up some stuff called insta Mold to try making molds with.But they do make a rubber that will not harm the knife.I wouldnt want to put a almost finished knife in sand as it could cause more clean up from small scratches than it would be worth.But making a rubber mold then cast the knife in plaster that doesent shrink or resin either would work.Then do the sand casting with the aluminum should work.

Now if the sheath will only be covering the blade you could just grind a dummy blade from aluminum or steel ,maybe a dummy guard and handle out of wood or something to get the general shape for the sheathmaker to go by.

Otherwise insure the fire out of the knife and take a chance.Or tell the buyer that he is responsible for the costs of the knife if it gets lost crossing the border,otherwise pick a state side maker to do the work...

Personally I have never had any problems sending knives into Canada.I woouldnt worry to much about it.
Bruce
 
Off the top of my head, going for cheap, quick, and easy, it seems like you might be able to use modeling clay (dollar store has good deals on it) and silicon caulk - either make an impression of each half and then fill and tape together, or to have a solid piece, attempt to make a 'sheath' of clay and then fill through top and fill holes.

- Jim
 
The rubber mold will give you a good copy. Make the casting using a resin that doesn't shrink.
As for the sand casting idea...Okay for casting another in metal, but you really don't want to scratch the original all over, do you? That's what you'd get...
 
Not trying to stirr up anything but if you have spent so much time and effort the last thing I would want to do it poor something over the whole thing. I'd try to get the buyer to handle the sheath business himself.

Added: I'd be more afraid that after all that effort the real knife wont fit quite right.
 
joe - brilliant suggestion (smacking my forehead right now....*ouch*)

I'll just rivet it to death to make sure I get a good solid seal. I'll probably have to do some clean-up work along the edge and spine afterwards...but I think it will work.
 
Dan,
Not to be a stick in the mud but we do alot of casting custom parts where I work. I also have a sculpting degree(how I got the job) and I dont think that the kydex will form enough to get an exact replication of what the original is.
I think this may be a bad Idea if the guy is spending anykind of money on the knife and sheath.

If you are determined to make a mold you will want to get casting rubber and build a form to hold the knife. You could get away with using 1/16" dowl to make a "seat" so that the knife will be horizontal.
build a form around the knife that will support the rubber when poured in(wood box with the seams filled with clay will work).
Coat the knife with casting release(to get it back out of the mold)

Have the box and dowls suspending the knife inside. pour rubber casting mixture into the box untill the knife is 1/2 covered.
Let cure.

you will need keys for the top half so drill some holes(1/4" should be enough) around the knife shape(once knife is removed from the mold).
nowcoat the first 1/2 of the mold with relase coating(so the 2 halves dont become 1 with your knife inside) and coat the knife.

fill the wood box all the way up untill th knife is completly covered.


Now, once the rubber has cured disasimble everything. you will need to cut a hole to pour your casting liquid into(this will harden into your knife)

use the original box to hold everything together.

we use a 2 part expanding foam that will rise out of the hole and go everywhere so be prepaired to have a box to pour the gushing stuff out(I can ask what the foam is)

before you pour the final casting stuff into the mold you will need to coat the inside with the same releasing agent and hope it doesnt stick together.


Dan,
I dont mean to discourage you but you may be causing yourself more trouble than anything.

I can get you the exact stuff we use but it aint cheap I dont think. I just hate to see you fowl up a nice blade and ship a duplicate that wont make a sheath that will fit the real knife.
Just trying to look out for you buddy!!! :D :D
 
The Canadian government has a surprise in store for you. When product enters the country they apply applicable sales taxes (up to 15%) just as if the reciever (sheath maker) is purchasing the product. In order for them to get the product released they will have to pay the taxes up front then reapply to be re- embursed for the taxes on their regular Provincial and GST tax forms. If they are not registered I am not sure how they would get the tax refunded. It works out for me because I am registered as a retailer but can take 3 to 6 months between regular filings to get the money back.
 
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