changing a bladed tool's sharpening angle

[boblob]

lets say i have a knife that was sharpened on both sides at 20 degrees what do i do if i want to change the angle to 30 degrees or if i want to change the angle to 15 degrees ?

if you know a card scraper lets say i have a card scraper that is sharpened on 20 degrees and i want to change the angle to 45 degrees
what is the process of doing that , do i need to completely remove the sechondary bevel/cutting edge and only after that i can put my new angle ?
thank you for the info!!!!

 

[stringer]

lets say i have a knife that was sharpened on both sides at 20 degrees what do i do if i want to change the angle to 30 degrees or if i want to change the angle to 15 degrees ?

If the final apex is sharpened at 20 degrees then sharpening at a smaller angle will thin the knife behind the apex and and sharpening at a more obtuse angle will make the apex more obtuse.

if you know a card scraper lets say i have a card scraper that is sharpened on 20 degrees and i want to change the angle to 45 degrees
what is the process of doing that , do i need to completely remove the sechondary bevel/cutting edge and only after that i can put my new angle ?
thank you for the info!!!!

That is not how card scrapers work that I am familiar with. The card scraper has a flat edge. It is just a rectangle not a triangle. You raise a burr off of one 90 degree corner to cut with with a burnishing rod. It really has no relation to what we are dealing with with knives. But maybe you are talking about something different, idk.

 

[boblob]

That is not how card scrapers work that I am familiar with. The card scraper has a flat edge. It is just a rectangle not a triangle. You raise a burr off of one 90 degree corner to cut with with a burnishing rod. It really has no relation to what we are dealing with with knives. But maybe you are talking about something different, idk.

i am talking about a cabinet scraper's edge it is a tool simmilar to a card scraper works differently

 

[boblob]

If the final apex is sharpened at 20 degrees then sharpening at a smaller angle will thin the knife behind the apex and and sharpening at a more obtuse angle will make the apex more obtuse.

and what about the other case if i have a knife sharpened at a 20 degrees and i want to convert it to a 15 degrees ?

 

[boblob]

If the final apex is sharpened at 20 degrees then sharpening at a smaller angle will thin the knife behind the apex and and sharpening at a more obtuse angle will make the apex more obtuse.

yes but how do i know that the conversion from the 20 to 15 degrees
or 15 to 20 degrees has been complete ?

 

[Benuser]

yes but how do i know that the conversion from the 20 to 15 degrees
or 15 to 20 degrees has been complete ?

Use a sharpie and a loupe to make sure the angle of the very edge has indeed been reduced to 15° as you were aiming for. I you're stopping before all ink is gone the old, 20° edge is still there and only some thinning behind the edge has taken place. You've turned a straight edge into a convex one. Nothing wrong with it, but it was not your purpose.

 

[Jovidah]

Just sharpen at whatever angle you want to make it until you achieve a burr. The burr means you achieved apex.
But if going at a lower angle it'll be a while before you achieve that since you're thinning out the entire shoulder of the existing bevel first.
Going higher angle is easy; just a few strokes should create a micro-bevel.

 

[Benuser]

Just sharpen at whatever angle you want to make it until you achieve a burr. The burr means you achieved apex.

But if going at a lower angle it'll be a while before you achieve that since you're thinning out the entire shoulder of the existing bevel first.

Going higher angle is easy; just a few strokes should create a micro-bevel.

All true. But depending on the steel, and the used pressure, a burr is likely to occur just before an apex is being achieved. Sharpie and loupe are safer. When the ink is gone on both sides and on top, the bevels certainly meet at the new, lower angle, and there's a burr. But a burr is a poor guarantee there's an apex. If I do insist on this point, it's because too often people tend to stop too early, and haven't achieved a clean edge, but an accumulation of debris on top of the old edge. A wire edge, very sharp, but very weak, failing at the first board contact, breaking off and leaving a moonscape behind.

 

[Desert Rat]

lets say i have a knife that was sharpened on both sides at 20 degrees what do i do if i want to change the angle to 30 degrees or if i want to change the angle to 15 degrees ?

if you know a card scraper lets say i have a card scraper that is sharpened on 20 degrees and i want to change the angle to 45 degrees
what is the process of doing that , do i need to completely remove the sechondary bevel/cutting edge and only after that i can put my new angle ?
thank you for the info!!!!

Not sure if you are talking about a scraper plane like the Stanley 80 or a scraper shave like the veritas or similar?

Either way they can be tricky to get the burnished angle correct and that is usually what is going on if it isn't working properly for you. I would encourage you to explore the burnished angle before you change the angle that the iron is ground. If you make the edge too thin it will chatter and act like a thinner iron that won't work nearly as well.

If I was to regrind the angle I would run the iron over a coarse stone using a scrap piece of wood as a guide ripped to the correct angle, or use a file, again with a guide.

That's probably clear as mud.

This might help...
https://assets.leevalley.com/Original/10092/54883-veritas-scraper-shave-c-01-e.pdf