Convexing - How much pressure?

H

HoosierQ

Joined
Feb 9, 2010
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Going to try convexing with the wet dry sandpaper and mousepad method...with stropping.

How hard does one press down on the paper? In other words, how much deformation of the mousepad surface does one try to achieve?

So I presume that too much pressure would result in "rounding over". Too little and would you not get convexing?
 
I find that this method is very forgiving of pressure, but get lighter on the pressure as you go up in grit, and you will get better results.
 
When you are converting from V edge to convex Just lay the blade flat, and put alittle pressure, about how much you need to push in packing peanuts (dent them). Once you have a convex edge, and you are sharpening use VERY little pressure, and raise the edge a tiny bit. On your strokes look at the edge and make sure you BARELY touching it.
 
A good measure of pressure is the weight of the blade. I never use more pressure than the weight of the blade. At the finer grits on leather strops, I partially supoport the weight of the blade, so there's even less pressure. :thumbup:
 
Pressure makes the curve, how much you use depends on the backing, thickness of paper, and blade grind.
 
Thanks a lot guys. I am getting a good mental image from you well written descriptions. Gonna give it a try this weekend.
 
I secure the edges of the wet-dry with clamps so it wont roll up behind the blade and dull it. Much pressure up to 2000 grit, light on the strop.
 
I am newbie at sharpening, at least serious sharpening, I had a old set of stones,,one a cheap combo stone, the other a soft ankansas stone, I have just gotten a set of stones , much larger and better quality I think, I did pay around $75 for the set,,it included 2 combo stones a leather strop and a bar of the green compound I hear so much about, I am very happy with the new stones,,my knives have never been sharper,,I am sure if I spent more money on a good system I could do a lil better, but for now I would rather spend my money on more knives ,,just my thoughts,,
 
Well...my first try at Convexing was, I think, a successs. I am certainly very pleased.

Used a mouse pad and a combo pack of wet dry sand paper in 220, 400, 800, and 1000. Ramped down the pressure as the grit went up. I then stropped first with green compound and then bare leather...not good horsehide but just an old weight belt.

I am very pleased with the polished edges and they are very sharp. I do notice that my sandpaper is much trashed after doing three knives...the coarser the grit, the worse off. So it looks like this method will consume a lot of sandpaper but who care...it works great!
 
The wear of the paper can be a pain and a plus, keeping a piece of worn 1k and 2k helps a lot when trying to get a better polish. To know if you did it right look closely at the shape and flow of your bevel, if the main grind flows smoothly to the edge then your probably close.
 
HoosierQ said:
Well...my first try at Convexing was, I think, a successs. I am certainly very pleased.

Used a mouse pad and a combo pack of wet dry sand paper in 220, 400, 800, and 1000. Ramped down the pressure as the grit went up. I then stropped first with green compound and then bare leather...not good horsehide but just an old weight belt.

I am very pleased with the polished edges and they are very sharp. I do notice that my sandpaper is much trashed after doing three knives...the coarser the grit, the worse off. So it looks like this method will consume a lot of sandpaper but who care...it works great!
Click to expand...

I get my sandpaper basically for free, as my dad owns a car body shop.
If you plan on doing a lot of knives using sandpaper get a belt sander. Or get wholesale packs of sandpaper like my dad does (comes in BOXES IDK how many sheets it has though).
I suggest the belt sander, fast and better finishes if done right.
 
knifenut

I rely very heavy on visual inspection...I use a magnifying glass...and what you describe is what I've got. I think it went very well...not claiming to be expert at it of course but everyone on this forum provided a wealth of knowledge that I was able to put to very good use.
 
Dumb question. When you put a convex edge on a blade using sandpaper and a mouse pad, do you pull the edge into the paper like you would on a stone, or do you let the edge trail the thrust of the stroke? When I convex an edge on a slack belt grinder, the belt moves into the edge (belt moves down/edge faces up).
 
YOU SHOULD NEVER DO THAT WITH A BELT SANDER, ITS DANGEROUS......


The answer your looking for is edge trailing :)
 
As knifenut said above, sharpening on a belt sander with the edge up is extremely dangerous as it can and probably will catch and send the blade flying very fast in whatever direction it wants. Always sharpen like you are stropping when using sandpaper, belt sanders, a strop or anything other than a stone.
 
I haven't had any problems holding edge up except on knives with a sharp curve at the base of the blade like a Wusthof boner. When the blade hooks the belt, it is the belt that goes flying. Does the edge down advice apply to belt sharpening on a platen as well as slack belt sharpening? I am not nuts about belt grinders for sharpening. I call them handle makers.
 
:
tiguy7 said:
I haven't had any problems holding edge up except on knives with a sharp curve at the base of the blade like a Wusthof boner. When the blade hooks the belt, it is the belt that goes flying. Does the edge down advice apply to belt sharpening on a platen as well as slack belt sharpening? I am not nuts about belt grinders for sharpening. I call them handle makers.
Click to expand...

:thumbup: I sharpen a few blades on a belt sander. 2 problems with edge into the belt,the shavings get thrown towards your face and you may ruin some belts.On the up side ,edge up is more agressive and you can get a
more uniform bevel on damaged blades.
But,when the belt rips.......I JUMP:D
 
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