The back side of a knife.

[Pattree]

Does anyone else “sharpen” the back of their knife blades?

Not all of them!

My Opinels come with a precise 90 degree edge which is famously effective on a ferrocerium rod, but they make excellent veg scrapers and wood dust makers as well.

I have a cheap chefs knife that I’ve been using for prepping some roadkill fox pelts. I sharpen this to a pair of tight 90’s. This is primarily for scraping the pelt but the edge is sufficiently precise that it can cut the wet hide beautifully straight.

I’m sure there must be other uses for a 90 degree edge.

 

[Kadushu]

I find the hump on a nessmuk is handy for scraping things. I tend to wack it a few times with a hammer to get a sharp burr.

 

[cbrdave]

I spent a few hours the other day putting a decent 90 degree on all my knives, just makes sense to me, great for scraping and sparking the ferro rod, saves the cutting edge too.

 

[Stew]

I spent a few hours the other day putting a decent 90 degree on all my knives, just makes sense to me, great for scraping and sparking the ferro rod, saves the cutting edge too.

I find it good to go slightly under 90 degrees - I don’t have a definite angle that I measure to but less than a square corner!

 

[cbrdave]

I find it good to go slightly under 90 degrees - I don’t have a definite angle that I measure to but less than a square corner!

Too be honest, I do it by hand so not exactly a 90, couldn't find my engineers square for checking but once they scrape and spark well I was happy.

 

[Pattree]

I find it good to go slightly under 90 degrees - I don’t have a definite angle that I measure to but less than a square corner!

Are you saying that one edge is under 90 and one over?
Or do you slightly hollow grind the back? That thought has never occurred to me. Thanks.

 

[Broch]

I do the opposite - especially on the chef's knives I make, I round the corners slightly on the top so they don't cut if you put a thumb on them. On some of the 'camp' knives I square the front 2/3rds and take the edge off the handle end of the blade or even tool a 'thumb grip' (I'm sure there's a proper word for that ).

 

[Stew]

Are you saying that one edge is under 90 and one over?
Or do you slightly hollow grind the back? That thought has never occurred to me. Thanks.

One under, one over - it’s slightly angled off square. For me, as it’s held normally, the left side is the higher (right handed) so when the knife is flipped the pushing edge of the back is ‘sharp’. Mainly used for ferro rod scraping. Only about an inch of the tip as the rest doesn’t need to be sharp. Towards the handle end of the back I’ll knock the corners off to be kinder to the thumb.
Doing this does make it look a bit odd visually so I’ve never sold a pre made knife with this as people don’t like it without understanding it first. I have done it to customers knives on request after they’ve seen it in hand.

 

[demographic]

Not so much gri ding them that way but I do find a good sharp scraper backedge handy to scrape the bark off a bit of wood, scrawp thorns off things and so on.
Scraping ferroceum rods with em always seems a bit contrived to me when they actually come with a bit of hacksaw blade specifically for that purpose.

 

[forrestdweller]

i actually rounded the spine on my whittling knife (homemade from old file) to stop it from giving me blisters. for scraping i often use a dedicated tool made from a short section of machete blade i found along the road

 

[Springchicken]

I used to file a square edge on the back of the old style Moras, purely to get a decent spark from a ferro rod. Thankfully, the knife I tend to use most now comes with a lovely 90 degree back.

 

[HillBill]

I mainly make bushcraft knives. By default, they have a squared spine for firesteels, bark scraping all that good stuff. My hunting knives/chefs/food prep knives come with the corners less sharp, more like the spine at 90, but the edges at 45.... because a sharp spine isn't needed. I've made a few with completely rounded spines, mainly by request. But those were few and far between. Normally dedicated wood carvers, though its normally only the inch or so next to the handle, as even a woodcarver needs a section to scrape with. Horses for courses.

 

[walker]

Round file to file a notch into the spine also works great for a fire steel

 

[demographic]

I use the back of the blade from one of my pen knives to scrawp the bark off bits of stick sometimes.
I don't even need to open the blade to do this, just use it closed.
A decent square edge makes that possible.

More or less an impromptu cabinet scraper.

 

[British Red]

I square the front 2/3rds and take the edge off the handle end of the blade or even tool a 'thumb grip' (I'm sure there's a proper word for that ).

View attachment 85967

I think the term is "jimping"