Different backing than leather strop for convexing

awestib

awestib

Joined
Dec 29, 2008
Messages
1,647
Hi everybody:
I have been working on (full height) convexing blades that are thick enough. All freehand and I use a thick leather strop with sandpaper. I am not super yet, It's alot of work, takes time and it's no easy but it's also almost (as I read from other folks here, same with me) meditation. I noticed however, that the blade is only just a bit convexed after, almost flat?! I assume the leather is just a bit to hard, just not quite enough give, and I already use quite a bit of pressure. So my question is, what else could I use and particularly get (I live in Canada, that means problems)? And, Mouse pad does not work! Too soft! Are there rubber pads available with different firmness grades?? There must be some marterial out there that comes in different grades of firmness I bet.
Thanks your your help guys!
Andreas
 
i have found that some packing material like bubble foam (not bubble wrap) is a lot firmer without being too soft. its sort of like the insulating strip they put on foundations before putting the floor plate on. i think i have seen some of this at the post office.

i was looking at an egg carton top one day and thought of cutting out several pieces and stacking them up to make a long enough pad and rubber cementing (if the cement will not eat the foam) an abrasive belt to it. a few layers thick should be enough give to form a good convex edge.
 
Thanks Richard, I have not even thought about "making" my own backing. Great ideas!
 
This is one of the reasons I went to convexing on a hard stone - I have complete control over the shape of the arc instead of having to swap out different backing materials. Easier to learn than you might think.
 
hh, i'll give you a ring sometime and tell you a few other methods (trade secrets i dont share often or post about) on convexing. i'm sure you'll like at least a few.

awestib, make your pad long and put it on a board at least 1" thick or 1 1/2" for finger room. make it about 14" long to give you clamp room. lay the board with the pad and abrasive from left to right and make sure its fastened down securely.

starting with the right side you will be at the left end of the board. lay the blade flat and raise the spine until you see the very edge just about make contact with the abrasive. with your index and middle finger spaced apart press down until the edge makes contact and push the blade away from you keeping the blade at the same angle.

pull the blade out as you push away from you and when it comes time to do the belly you raise the handle straight up following the curve of the belly. stop when you reach the tip. switch ends and repeat for the left side. watch for a burr to form and when it does you switch to a strop and remove the burr.
 
If you can freehand a regular bevel, the convex shape is no more challenging and you then know exactly what the apex angle is, how steeply or gradually the curve breaks away from the edge, and its no less meditative/cathartic. the only real difference is that you'll probably want to polish the blade face on a strop of some sort to blend the scratch pattern - and old scrap of leather loaded with black compound from Sears gives a nice satin finish. It also gives you the advantage of using whatever type of stone you want - diamonds, waterstones, Spyderco ceramic, and the ability to use an edge-leading stroke for burr removal.

Just a thought - it doesn't get recommended very much but its a lot easier to learn than most people would think.
 
I've been playing around with different backing lately, using something like a catalog under sandpaper. Both are binder-clipped to a piece of 1/4" thick glass, under which I've stuck some rubber feet to elevate it a bit (gives a little 'finger room' as mentioned previously). I've been varying the firmness/thickness of my 'soft' backing by simply changing how many catalog pages are underneath the sandpaper. My preference is gravitating towards a 'gentler' (thinner) convex, so I've gradually been reducing the thickness & softness of the backing under the sandpaper. I used this method to thin & polish the already-convexed blades on a couple of Opinels recently.

Like many others here, I've constantly kept my eyes open for different materials which might be suitable for the backing. As one's skill develops, you can select a backing that nicely complements your use of pressure (some will lean into it harder than others), which allows you to get the results you want, by tailoring your backing material to fit your particular skill & technique. As HH mentioned, you can convex on a hard stone too. My particular method, using the gradual thinning of the paper 'stack' on the glass, is sort of gradually moving me in that direction. At some point down the road, I can see just using the sandpaper on the glass alone. I've sometimes done this anyway, especially in the finishing stages, after I've already established the convex bevel on the blade. I'll sometimes go to the sandpaper on glass, to finish the very edge itself (absolutely minimizes the chance of rounding that final, thin edge, as might happen on a soft backing).
 
HeavyHanded, what is your basic movement though? Going forth and back on the stone and rocking your wrist?
Thanks!
 
awestib said:
HeavyHanded, what is your basic movement though? Going forth and back on the stone and rocking your wrist?
Thanks!
Click to expand...

That's pretty much it, I generally use a back and forth and as I get down to removing the burr it'll be mostly forward. I usually start out just below the apex and work away on that for a few as I slowly (to steal a line from Obsessed by Edges from another post) sneak up on the apex. Since the bevel is convex there's less steel to remove at the apex when working with a flat stone, so I just give it a handful of passes and slowly lower the spine as I keep at it. The slower you lower, the smoother it will look, though it may never be as satiny smooth as a sandpaper job. I then repeat this a few times till I've raised a burr, flip, etc - at this point the basics are the same as a V grind. I always spend a little more time just shy of the apex - pretty sure this combats the tendency to make the bevel more obtuse - which is the only pitfall to this technique, actually feel its easier than doing a V bevel once you get a feel for it. A bit of extra work on the strop using the same philosophy puts a very nice finish and smooths out any grind pattern irregularities - of which there will be some -don't be alarmed as you go. I've done two conversions of sabre ground blades to full convex using just stones and, compared to using sandpaper by hand, it doesn't take any more time though it can look alarmingly raw in the beginning. The first of these I did because I wanted more meat at the very tip than the sandpaper technique would allow me to control. I wonder if I can maintain it like this as well? and that's how I've been doing it since. I generally stop at the low to medium grit edge and it's very difficult to remove the burr from an edge-trailing sandpaper technique - no such limitation with a hard stone.

Hope this helps
HH
 
HeavyHanded said:
I went to convexing on a hard stone
Click to expand...

Me, too. I don't like the sandpaper/mouse pad method. I convex with my KME Sharpener. First I put a primary and then a secondary angle on the blade...

http://www.youtube.com/watch?v=GvKG_8k7FPA

Then I strop them into a convex edge...

http://www.youtube.com/watch?v=xSOh4GuCFVk

I once tried putting three angles on the blade before stropping, but it turned out to be a lot of extra work for nothing...

http://www.youtube.com/watch?v=Tb6pLo5ieFs

Happy sharpening!
 
awestib said:
Hi everybody:
I have been working on (full height) convexing blades that are thick enough.
Andreas
Click to expand...

the convex on stone thing is probably not the best answer to someone who is essentially regrinding blades. at least that's how i understant the bolded part.

i'd suggest 2 things : buying a belt sander as this is an insane amount of work, and not trying to make your blade zero ground convex because i highly doubt you'll ever find a backing that allows enough curve to get a decent final edge angle out of a zero grind. this last one may sound obvious.
 
I've been zero-grinding all of the convex edges I've been doing. On thicker/harder blades that'd be tougher to accomplish on soft backing, I've used my Magna-Guide & diamond hones to put a relatively shallow (low-angle) V-bevel on the edge beforehand, then used sandpaper to finish the convex. Using the diamond hones first makes the heavy metal removal at the edge a good bit easier & quicker. Doesn't take as long to convex the resulting V-bevel afterwards. I grind the V-bevel at a pretty low angle, because the convex will almost always result in a slightly thicker edge bevel when finished. If you're careful about it, you'll more-or-less leave the very edge untouched (should be an excellent edge, coming off the guided diamond sharpener), and just focus on rounding & smoothing the shoulders of the bevel (as mentioned earlier, 'sneak up' on the edge, but don't touch it).
 
awestib said:
Hi everybody:
I have been working on (full height) convexing blades that are thick enough. All freehand and I use a thick leather strop with sandpaper. I am not super yet, It's alot of work, takes time and it's no easy but it's also almost (as I read from other folks here, same with me) meditation. I noticed however, that the blade is only just a bit convexed after, almost flat?! I assume the leather is just a bit to hard, just not quite enough give, and I already use quite a bit of pressure. So my question is, what else could I use and particularly get (I live in Canada, that means problems)? And, Mouse pad does not work! Too soft! Are there rubber pads available with different firmness grades?? There must be some marterial out there that comes in different grades of firmness I bet.
Thanks your your help guys!
Andreas
Click to expand...

Stropping requires barely any pressure at all. The only pressure should be the weight of the blade itself.
 
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