DIY Molded Scales?

Varga Knives

Varga Knives

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Aug 12, 2006
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A friend of mine just asked me to check out Johnny Strong Knives and it turns out my friend was right, I do like them. ScoutAssassin_1.jpg He molds his handle scales and while it limits the handle shape there are some interesting things that can be done. Is this something that can be tackled by the home user without too much expended in start up costs? I looked into Delrin, Noryl GTX and Valox but I can't really say how friendly they are to work with or if they are even available to individuals (I know Delrin is). Anything better to work with? Should I forget the whole thing? Is it as simple as pouring a liquid into your mold (like making cupcakes) and letting it set?

Thanks!
 
Thermoplastics (plastics that are melted then molded) shrink considerably as they cool. Under ideal circumstances Delrin shrinks about .018" in/in. it is way more than that under less than ideal parameters.

Because of this, the inside of the part (which cools slower than the skin) continues to shrink after the outside has solidified. This makes parts warp and develop sink marks and internal voids.

Thermoplastics are molded under very high pressure which slightly compresses the plastic in the mold. The mold is held together in a press under many tons of pressure and the molten resin is injected under several thousand pounds of force and "packed out" under at least 5,000 PSI and sometimes up to 20,000 PSI force to compress the plastic so there is material available in the part to prevent sinks and voids as it cools.

This is about as far removed from melting plastic and pouring it into a mold as you can imagine.

BTW, hot high pressure plastic is a little dangerous to be around.

You might look into some of the castable resins such as specialized epoxies, urethanes and polyesters.
 
Or shape/machine the scales from solid slabs of whatever you want......probably a lot easier and cheaper than setting up an injection mold.
 
I know K-9 handler here did some clear epoxy handles, I'd hit him up with a pm or search through his Becker posts, the handle was on a mirror polished BK-5 if I remember correctly.
 
There is some stuff called shapelock which is a Ultra-High Molecular Weight Low Temperature Thermoplastic. You can mold it at 160 fahrenheit, etc. It is supposed to be as tough as Nylon or polypropylene. It is made in california I think. I read about it some time ago so give it a google and you should be able to find it. I do not know if that will fit your needs or not but it is worth a look. I think its name is its web address as well. They use it for prototyping or something.
Cheers.
 
It sounds like there isn't yet a user friendly material for the hobbiest to try out that doesn't have severe compromises. It would be nice to find something that would melt at around 400 degrees and could be poured in a mold and sets at room temperature; is not effected by wide temperature extremes; impact/scratch resistant; won't absorb chemicals; and cost about $5 per pound. I would ask Mr. Strong for some detail on what he is using but his only contacts are through social media which I don't play with. Oh well, I just thought it would be another fun thing to try out down the road.

I will have to pick me up some of that shapelock stuff!! I don't know how well it would work as handle material but it sounds like a hell of a lot of fun to play with. I can think of all sorts of neat uses for it on my boat.
 
strider214 said:
It sounds like there isn't yet a user friendly material for the hobbiest to try out that doesn't have severe compromises. It would be nice to find something that would melt at around 400 degrees and could be poured in a mold and sets at room temperature; is not effected by wide temperature extremes; impact/scratch resistant; won't absorb chemicals; and cost about $5 per pound. .....
Click to expand...

That would work well with a steel that HTs with a torch, gets Rc68 on a motor oil quench, has superb edge retention at Rc64, will never wear, and costs $5 per pound. :D
 
I have some "Zytel" glass reinforced nylon and some "Delrin" POM pellets for injection molding here left over from a previous life if anyone wants some...
 
Why limit your thoughts only to thermoplastics? There may be two part resins that you could tinker with. These can work well in a simple setup. The trick is to make a female mold of the part you want to create. This is done by first making an example the old fashioned way. You can then build a box and rubber mold of it. I assume there is info online describing proper venting channels etc. Resin is "injected" using through a tube inserted into the cavity at the bottom of the female mold until it begins flowing out of the vents on the top. A peristaltic pump works well for injecting resin, but isn't in most hobbyist toolkits.

Other than available resins, the primary drawback is the possibility of air bubbles on the surface of the finished part. This can be minimized to a certain extent with a few additional steps, but not completely eliminated in a basic process like the one described above. It has been years since I molded anything this way, and I am just starting to dabble in making knives, but I don't think I would recommend it for this. Regardless, it is a fun little process to fiddle with.
 
Makes me think of resiprene c handles on swamp rat/scrap yard knives. I have no idea how you would go about making something like that, but I think it would be a pretty cool project. Maybe Johnny Strong will tell you how he does it, or at least the material. If you give it a try or find out anything interesting you should post it.
 
strider214 said:
It sounds like there isn't yet a user friendly material for the hobbiest to try out that doesn't have severe compromises.
Click to expand...

You might like to poke around the Smooth-on Inc website. They have a really good selection of moldable products, including castable urethane plastics, and sell trial sized kits. I've done business with them, and they are good to work with.

- James B
 
Smooth-on is great. A very helpful crew there and all sorts of stuff for casting most plastics, silicons etc. Based in Easton PA.
 
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