Box straps chipping edge

C

coyotes72

Joined
Feb 23, 2016
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The other day I was helping a friend open many boxes and I cut open probably 15-20 boxes that were held closed with tape and straps. After I was done, I noticed the edge of my Benchmade 665 was dull and rough, I guess it could be called micro-chipping. My question is: is this typical for the plastic straps to cause micro-chipping, or is it more likely that I made the edge too thin when I sharpened it. It is 154cm steel at 57-59 hrc I believe, since I was sharpening freehand the edge is somewhat convex.

If I left out anything important please let me know. I tried the search function but got nothing useful so please post a link if this is a repeat question, thanks in advance for the information.
 
My guess is that you made the edge too thin and perhaps you were twisting slightly?
 
if your not stropping, a wire edge will feel very sharp when you finish on the stone but will roll easily and then it will seem dull. you can see the spots where it rolls, and it could look chipped i would say.
 
Neko2 said:
My guess is that you made the edge too thin and perhaps you were twisting slightly?
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My experience as well. Slip the tip portion of the knife under a thick plastic strap and twist to cut. Part of the tip is dull. That you can call dull or microchip. In my case, the edge is not thin, nor I believe there is a HT issue. It is just because the knife is very sharp.
 
I was using sandpaper to sharpen, don't know if that makes a difference though. I was not twisting purposely, I either lifted with my fingers or pushed.


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My benchmade 154cm edges roll fairly easy. I find a minimum of 35° inclusive or more is needed for my use with this steel.
 
jpm2 said:
My benchmade 154cm edges roll fairly easy. I find a minimum of 35° inclusive or more is needed for my use with this steel.
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This is spot on. I sharpen mine to roughly 18dps or 36 inclusive. Anything less and you'll lose the durability, especially if it experiences any lateral force.
 
Without buying a gauge or anything, is there a good way to find the angle?


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Double the length of the thumb stud. Set the blade down on the stone/paper and then rotate up until the thumb stud is off of the stone/paper about as far as it is long.

Not quite an exact science, but it's a good visual reference that's already on the knife and should be pretty reliable.

If it still feels a little thin you can always double it or use some sort of spacer, like a bottle cap, to act as an index, but I bet double the stud length will work fine.
 
coyotes72 said:
Without buying a gauge or anything, is there a good way to find the angle?


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Click to expand...

you can use your iPhone Compass app, there are two functions, one is compass and the other is a fairly accurate angle finder. it'll give you a rough idea.
 
Thanks guys, I have the edge skinny enough to where when I set it down on a flat surface it is almost touching the thumb stud, so I definitely have it too thin.


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Rather than take out the whole edge, try putting a 40-degree inclusive microbevel on it (assuming it's at 30 degrees now).

If you have a protractor, you can check the edge angle with a piece of wet/dry sandpaper stretched over a block of wood. Tilt the block up until you get to a 15-degree angle (30 degree inclusive). Then paint the edge with a Sharpie and do a dry pass, holding the knife as level (parallel to the floor) as you can and see where the ink is scrapped off. If you're scraping off ink at the very edge, your edge is greater than 15 dps. If you're scrapping off ink at the shoulder of the edge, you're edge angle is less than 15 dps.

By varying the angle of the block with the protractor, you can zero in on that angle of your edge.

If it's 15 degrees, try a microbevel of 40 degrees. That should hold up to your needs.

Make sure when you're done that you have removed the burr along the edge -- then you won't have a wire edge.
 
Could it be an operator head space error? I've never had rolling and I sharpen lower than the thumb stud. If you need to steepen the angle a littlei can see that but double the thumb stud seems awfully steep.
 
me2 said:
Could it be an operator head space error? I've never had rolling and I sharpen lower than the thumb stud. If you need to steepen the angle a littlei can see that but double the thumb stud seems awfully steep.
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What do you mean by head space, I have a feeling that it means something different than with guns.

Also, as far as a microbevel, it should just look like a hair laid along the edge as far as thickness right?
 
Those "plastic" straps have fiberglass reinforcement and they're also usually dirty. Dulled edges are pretty much par for the course when cutting them.
 
FortyTwoBlades said:
Those "plastic" straps have fiberglass reinforcement and they're also usually dirty. Dulled edges are pretty much par for the course when cutting them.
Click to expand...
You're right, I used to have to cut those damn things all the time and quickly learned that my finely honed pocket knife was the wrong tool for the job. I started using a ring cutter instead.
 
It's a joke for operator error. Like when a mechanic tells a driver they recommend removing and replacing the nut behind the wheel.

We must not be taking a the same strapping. The stuff I'm thinking of is just plastic, no fiberglass.
 
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