Plastic Knife

[alfonzo1955]

I want to make a plastic knife, just for fun. What material should I use? I have with me currently plexiglass and lexan. Would other polymers work better?

 

[MNofUSN]

ya if you can get your hands on some; polyetherimide (aka PEI)it is a 30% fiber glass with a rockwell some where in the 75 to 150 range

you may also want to check out polyamide-imide or Polybenzimidazole



I'm a huge Industrial chemistry buff

 

[theHobbyist]

Sounds like a prison shank you're wanting to make =\ FWIW, I made one out of lexan, wasn't very pretty, and it didn't hold an edge

 

[MNofUSN]

oh, here is a website that says exactly this

http://www.newton.dep.anl.gov/askasci/mats05/mats05041.htm


was making sure i spelled Polybenzimidazole correctly haha no joke

 

[MNofUSN]

I made one out of lexan, wasn't very pretty, and it didn't hold an edge

its not going to hold a great edge do to its make up.... its the same principle of why certain steels have better edge retention and rust resistance over other steels; it all about what they are made up of

god I feel Geeky today

 

[alfonzo1955]

Thanks for the replies, but let me rephrase my question. What material would you recommend that I can easily buy on a student's budget? I have no monies =(

 

[MNofUSN]

if you have the skill melting down some 2l soda bottles & layering it like Damascus works kinda well, just have to be careful about harmful fumes and over heating it... plexy could work, will most likely brittle apart..... may want to try a combo of plexy and fiberglass may be ably to do something with that


I will have to do some research and personal tinkering and find out

 

[theHobbyist]

if you have the skill melting down some 2l soda bottles & layering it like Damascus works kinda well, just have to be careful about harmful fumes and over heating it... plexy could work, will most likely brittle apart..... may want to try a combo of plexy and fiberglass may be ably to do something with that


I will have to do some research and personal tinkering and find out

Done that once before for something else... not as easy as it would seem lol

To the OP, what are your intentions for this?

 

[MNofUSN]

correction plexi and lexan

 

[alfonzo1955]

No intentions, just something I want to try. Saw cold steel's polymer knives and I was like "hey, I could do this too"

 

[weech3]

Withdrawn.

Buy a cold steel; cheaper and easier.

 

[MNofUSN]

haha agreed..... did some research and some formula crunching. you cant mix the 2 together do to the fact that plexi is a synthetic polymer and lexan is a type of polycarbonate; however, if possible you may be able to shape your blade out of the plexiglass and coat it with the lexan. plexi melts around 325 and lexan 280 (use your oven to melt it??? option). This may work, not positive but it is a way to go...... to sharpen it use sand paper and some veg. oil to keep the friction down


that's all i got...... hope it helps and good luck

 

[Stacy E. Apelt - Bladesmith]

G-10 is cheap. It is hard, polishes well, and can be shaped with files and sandpaper.
Even Micarta if you are just playing around.
An alternate that will run a few bucks more is Carbon Fiber. That will actually make a knife.

 

[phillipsted]

+1 on the micarta and G10. Personally, I would look for a piece of 1/4" linen micarta material that is sold for knife scales. This stuff cuts and files well - but is hard enough to take a good edge. It won't be very durable if you intend to stab it into car doors and whatnot - but will turn out a serviceable shank...

TedP

 

[foxx]

If you choose to play with G-10 or micarta USE A RESPIRATOR! Don't sand that stuff where you live, do it outside. Wet sanding keeps the dust to a minimum, but you still want to clean up, hose off, that area when finished.
There are a few places to buy G-10 knives, most are short and oriented towards concealed/self defense knives.

I've cut out a tomahawk from a 3/4" thick slab of G-10, I've sanded down the lowest part of the handle just enough to swing it. It's tough and abrasive, it chews up blades and sandpaper very fast. But, in the end you will have a very tough knife. I have beat the hell out of some fence posts with my G-10 hawk, and have only hurt the fence posts, and my hand.

 

[james terrio]

I'd stick with G10. Micarta would work, I'm sure. Carbon fiber looks really cool but it's costly. I made a letter-opener for a fellow forumite out of CF not long ago, and it gets kinda fuzzy when you take it down to a thin edge... this raises some concerns in my mind about de-lamination if it was used for anything strenuous.

By all means, be careful about the dust no matter what material you choose.