diy sharpness tester question

M

matlocc

Joined
Jan 29, 2016
Messages
52
can anyone give me an idea how to build one? From what I can find you place something on a kitchen scale and then try to slice thread or fish line by pressing down (no pulling/pushing) Then try to see how much pressure is needed. Does anyone have pictures of a DIY setup?
 
I'm brand new to the game myself, but personally I'm planning on just using a thread or thin fishing line and draping it over a blade and then adding weight to the ends of it. When the thread cuts, weigh how much it took to cut it. It's all really relative for me, I just want to know if something is "sharper" or "duller" in order to gauge my ability to sharpen.
 
There are threads here and there about various "sharpness tester" devices. The problem is, they only test what the test can test. I.E., the ability to cut thread doesn't necessarily correlate to the ability to cut rope or meat or wood or cardboard.

Then there's the question of what you are trying to find out: Just edge sharpness? Or edge holding through a certain amount of cutting tasks?

For practical tests, you don't need anything nearly this sophisticated. Phonebook paper is an excellent indicator of sharpness. Hair shaving is a time honored method for a certain level of sharpness. Murray Carter's "Three Finger Test" of sharpness is used by many also. I'm still not very good at the 3 finger test, but I think I'm getting better with it.

Brian.
 
Here's one I made from an aluminum can and a bolt. It worked surprisingly well.

stringcan.jpg
 
Here's one I made that can test poundage needed to make a draw cut or pressure cut. The upgraded one can get a pretty accurate reading for both dynamics and with some patience you can get retention numbers as well. I use it with 3/8" Manila but any cord could be used.


[video=youtube;2pxtGRaJT2I]https://www.youtube.com/watch?v=2pxtGRaJT2I[/video]
 
Sharpness testing :

After sharpening your knife if you approach your arm hair to whittle a few (take multiple curls off the same hair while it is still in your arm) and the hairs pull them selves up roots and all and jump off your arm before the blade gets there . . .
then your knife is SHARP.

But if the hairs stay planted and you can only whittle curls off them the knife is only sharp.

Simple.
 
Wowbagger said:
Sharpness testing :

After sharpening your knife if you approach your arm hair to whittle a few (take multiple curls off the same hair while it is still in your arm) and the hairs pull them selves up roots and all and jump off your arm before the blade gets there . . .
then your knife is SHARP.

But if the hairs stay planted and you can only whittle curls off them the knife is only sharp.

Simple.
Click to expand...
That must be what happened to the hair on my head, got my knives a little too close over the years.
 
singularity35 said:
I just touch my edges these days. I used to do the hair whittling thing but that got tiresome.
Click to expand...

I've sharpened enough now that i can feel if it's getting to where I want it to be.
After I come off the stones and strop I just drag the edge through my arm hair and if it will tree top the hair that's good enough.
 
If I look at the edge and my eye starts bleeding, I know that I have it sharp enough.
 
Why do you need fancy testers? Body hair plus junk mail/phone books should be sufficient
 
I use a wood frame on a kitten scale. Search for Edge On Up. The make a few sharpness testers. You can also try light thread with a set amount of weight faired over the edge for slicing cuts. The lower the weight and shorter the length of edge needed to cut the thread the sharper the edge. If recommend a light thread or fishing line for pushing on a scale and light twine or something braided for the sing test.
 
Dang, after reading all the "my knife is so sharp that....", I sure wish I had asked my Grandpa his sharpening secret. My Grandma used to bake homemade bread in the oven. Using one of my Grandpa's freshly sharpened blades, she could slice fresh bread so thin, each slice only had one side to it.

Dude
 
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