How can you tell if your edge is too thin?

J

jawilder

Joined
Jun 27, 2006
Messages
2,331
I am finishing my first blade in 1095. it has a very clear temper line/hamon from clay quenching. I think I ground it way too thin.

the blade is 5.25" long, 1.5" wide and 5/32" thick ground to a zero edge. I didn't mean to take our that far but it happened. I tested it by hacking a very hard mesquite log and don't like the results. about 3/16 of the edge bent and tore. it didn't chip as much as just tore. I tempered 2x at 2 hrs at 410.

oh, only about .5" wide was affected. please tell me that the edge was just too thin.

by the way, I normalized 3x, heated to 1450 and quenched in l8er

thanks,
Jason
 
Hey there Jason. I feel your pain. As said already, I would suspect your austenizing temp - even with a good heat series for the setup, you may have some feral carbon in 1095 quenched from 1450. Also, depending on soak time/atmosphere and how/when you took it to a zero grind, you may have a decarb zone, through and through, at that ragged edge.

If it were me, I would likely grind it back - cool and careful like - and test again. (Grind a new flat at .025" or wider and thin to centerline.) Either way, it's a place to start, you'll have learned something about your methods and may end up with a decent "Plan B" type blade (some of my best)...

It may seem like a mile, but you are close - real close.
Hang in there and keep picking away. Hope all is well buddy. AWL
 
I agree with Andy.

Grind it back ( at 1.5:" wide you have lots of room) and put a new edge on it . Make the new edge at 30-35° included angle. I bet it chops much better after that.

I don't see any big problem with your HT and temps, assuming you gave it a bit of soak time.

Lets talk about testing a bit.
If you make a big camp knife and try to slice tomatoes...it may not cut well. If you make a skinner and try and chop mesquite....the edge may chip and/or bend. Test a knife with tests that simulate the use it is made for, or the edge will either not cut well, or it will fail. A brass rod test can tell you if the HT is about right, and slicing cardboard can tell you if the edge geometry is good for a slicer. Cutting 2X4s will tell you if a chopper edge is robust enough. Abusing an edge will tell you nothing. Chopping violently into hardwood, cutting steel,bending, and other extreme tests are not good ways to test your knife edges, unless you are testing to see when they will fail.....which they will under these type of tests. There are things to be learned from destruction testing, and such tests are good to do from time to time, but try and test a user in a task related test.

This is why we choose different metals for different tasks - 1095 is great in a thin edge, and will slice up a ream of paper , but chop poorly. D-2 in the same edge will chop forever ( almost) but may not slice paper well at all.

Match the steel ,the edge geometry, blade size and thickness, HT, and testing to the desired use and you will rarely have a failure.
 
thanks everyone. 1450 is a little low. I'll try 1475 next time. I took the edge down to .013 and made a few chops in 3/4 plywood and it held up. this knife will be a wedding present for a friends to give to her new husband. I doubt he will be doing anything other than skinning deer but wanted to make it big enough to make it a general hunting knife.

I etched it last night with vinegar and will polish it tonight. seems to be holding up well now.

20120217_112551.jpg
 
Jason, giving this knife to the bride sounds like the start of a Bluegrass murder ballad. :D

The amount of heat retained in the edge may have not been enough to harden it. It helps to have cat-like reflexes when qunching.
 
I have not ground it to a final edge yet. Still at .013 but did the brass rod test and everything seemed ok. I'll just have to guess that it was waaaay to thin for chopping on well seasoned Mesquite. Lesson learned.
 
In my opinion, alot of custom knives are way to thick behind the edge than they should be. Finding the limits of how thin an edge can be and then adjusting how much you leave on future knives is much better than making sharpened crow bars and not daring to go thinner.
 
JM that is my thought exactly. what is the point of trying to convince a potential customer to buy a custom knife if the one at Walmart will do just as good
Jason
 
Thanks Andy. I admit that I looked at a few of yours before putting this one on paper

It is polished now and will post pictures when it is handeled and finished
Jason
 
You must log in or register to reply here.
Back
Top