Convexing questions, equipment, belt sander, paper wheels, a question smorgasbord

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keyser223

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Apr 1, 2011
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After attempting to convex my ratmandu using the sandpaper method, I finally gave up several hours later. I was going to go out and get the paper wheels at the local woodcraft as I already have a grinder. A few days prior to doing so, I stopped in to visit my parents and realized my father has 2 of the Kalamazoo 1x42's in his shop that I now have permission to use. I practiced on some old really damaged knives and a cheap cold steel heavy machete on some worn 80 grit (only belt I had at the time) and got fairly comfortable using the sander.

I've read that I can get the leather belts from Lee Valley, but what belt grits do should I purchase in addition to this and where should I look for the finer grits on x-type?

Secondly and this may seem really dumb, but I'll readily admit to being very new to sharpening. I purchased a dull hatchet and was reading how to sharpen hatchets and axes and came across this link:

http://www.youtube.com/watch?v=CKpsFLNvTD4

I may be off, but the hatchet was essentially convex? So, I started with an arkansas stone I had and went to sharpening the hatchet in the circular motion demonstrated above and it sharpened right up, then I wrapped some 400 grit wet/dry around a block I had laying around, then to 600 and then 1500 using the same motion. Finally I stropped it to polish it up and was sharp enough to shave with. Could this same method be used for sharpening convexed knives? I'm thinking it might be handy in the field.
 
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I see no reason why you couldn't (or shouldn't) sharpen a convexed knife the same way. It's a skill thing, and most find it easier to sharpen convex blades with an edge-trailing (stropping) stroke on softish backing (with sandpaper), or by using a belt grinder. But, if your technique is sound enough, that 'circular' motion with a stone can be used on pretty much any blade (axe or knife, convexed or not). The proof is in the results you get. So, if you like what you got, no worries. :)
 
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The first set of belts I got for my Kalamazoo was 120, 220, 320 and 400, with a 15u and 9u mylar belt for a bit more polish. I also purchased two leather belts, and use one with green compound, and one with white. I purchased my belts from EconAbrasives, they've got the SurgiSharp leather belts for $12, and regular grit belts for under a buck each.

The sander is an amazingly easy way to get a superbly sharp convex edge in a very short time. I sharpen semi-professionally on the weekends at a local sporting goods place, and the Kalamazoo and Trizact belts are my go-to method.
 
if you want an edge that is more durable for chopping, dont go over 400 grit with the belts. to me anything finer is overkill and will not last as long as a coarser toothier edge.

you mentioined the paper wheels. the grit wheel will only do a v edge but the slotted buffing wheel will work to remove the burr on a v edge or convex edge. i maintain my edges on the slotted wheel by making a few passes on each side to bring the edge back. the slotted wheel works better than a leather belt for stropping an edge. a buddy who had a tormek with a leather wheel had me touch up his freshly sharpened wood chisels. he said the edge was much sharper than what the leather wheel made them.
 
I've had very good luck by working up a Burr on my 2x42 with a 220 belt, then finishing the edge with the slotted paper wheel with green compound. Hair whittling every time, no exaggeration.
 
Yes you can use bench hones to put a convex edge on your knives just like you did with the ax. In fact hones/stones are my prefered method for convex sharpening. For belts you could checkout Pop's knife supply. Truthfully all you really need is a coarse grit, fine grit and a polishing compound. It really isn't the equipment that makes for a sharp edge it is the person sharpening. Murray Carter can get a better edge than most people just useing a cinder block and cardboard. The more you sharpen the better you will get no matter what you use.
 
db said:
Yes you can use bench hones to put a convex edge on your knives just like you did with the ax. In fact hones/stones are my prefered method for convex sharpening.
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Mine as well - I initially attributed my good results from convexed blades to the sandpaper, but after doing a few V bevels on sandpaper, and few convex conversions on stones, realized its all in the shape of the cutting edge - doesn't matter how its achieved.

Only drawback to the circular method is that is has no microteeth aligned with the cutting path, though the somewhat erratic grind pattern seems to make up for this when doing rough cutting anyway.

I did some brief experimenting with circular sharpening for smaller knives and it makes for a respectable edge - still use it on my axes with a puck-shaped stone.
 
With small pocket hones, like my DMT 'credit card' hones or Dia-Folds, I've usually used the circular motion to set the bevel and raise the burr. Once that's done, I finish with strokes perpendicular to the edge, to get those 'teeth' lined up. Only takes a few passes, with whichever hone you please, depending on how much 'bite' you want in the finished edge.
 
Thank you all for the input and thanks DB for the link to Pops Knife Supply, order has been placed. I ordered a 220 grit, 400, 600 and leather belt. I think I will get the paper wheels too for quick touch ups.
 
I think you'll be really impressed, the belt is an amazingly quick way to put on a great edge. I've not tried the wheels myself (no reason, already have a belt system) but they are reputed to be excellent as well.
 
Komitadjie said:
I think you'll be really impressed, the belt is an amazingly quick way to put on a great edge. I've not tried the wheels myself (no reason, already have a belt system) but they are reputed to be excellent as well.
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Do you use the trizact "gator" belts?
 
I will be impressed if I don't ruin my knives, ha. I'm going to practice on several old ones first of course. I should not have attempted to hand sharpen to convex my ratmandu, I can't tell if I've altered the grind or if I've just removed finish, but will hopefully get it corrected on the belt.
 
I actually use a Trizact with a different pattern, I'm not sure which one it is. They're made custom by Doug Rising, the abrasive is pyramidal in nature instead of rectangular like the Gators. I've not had a chance to use the the Gator, but it at the Norton "NORaX" belts are also supposed to be quite good.

I've actually had pretty good luck with just plain old grit belts as well, although they don't last anywhere near as long as the Trizact does. At the moment, I use Norton Blaze belts in (60, 80 and 120 as required) for any serious stock removal (repairing a broken-off tip, taking out serious nicks, thinning a massively obtuse edge, etc) then the Trizacts from A65 down through A3, then two leather belts (one with green compound, one with white). A lot of the method depends on the edge I'm going for, and how much time I want to spend on it. For a fast edge, it's really hard to be a fresh 320 grit belt to raise a burr, then the leather with green compound to buff the burr off and polish. The resulting edge is fairly toothy and makes a great working finish with very little time invested.

Keyser, I'd suggest you make a run to your local second-hand store, and pick up a handful of old kitchen knives. They can usually be had quite cheaply, and make great practice. Keep a tub of water close by, and if you can feel any heat at all in the edge with your fingertips as you take it off the belt, just give it a quick dunk. Remember, you can't hold onto something over 150 degrees, roughly, and most tool steel doesn't even start the temper process until 400 degrees, so you've got a pretty fair window there. Be careful near the tip, and don't draw the tip more than about halfway across the belt, or you risk rounding it off a bit. You'll be able to pick it up easily in the first couple practice knives, angle is nice and easy to hold because you can just keep the spine a steady distance from the belt. Remember, as you approach the tip you will need to raise the grip a bit, the section of the edge you are sharpening needs to be PERPENDICULAR to the motion of the grit at all times. Once again, you'll see that easily on your first practice knife with the belt. Don't think about it too much, just go give it a shot. :thumbup:
 
keyser223, forget the leather belt. the slotted paper wheel will work a lot better.

the trizact belts work great. i have a 400 grit that i have had for over 10 years and i just about have woren out.
 
Doesn't matter if it is paper or leather. They will both polish the same if the same angle and grit/polishing compound is used.
 
db, my buddy that had me touch up his wood chisels used a tormek for years to sharpen them on. he told me the chisels i touched up on the slotted wheel were much sharper than what the leather wheel made them. he had been in the remodeling business for 15 years before i met him so i would think he could tell which done the better job.
 
I'm sure he could tell what was better/sharper. Doesn't mean that the paper wheel was better though. Could be your better sharpener, the grit is finer, the speed of the two wheels are different, size and curve of the wheels are different. Could have been alot of reasons. You like to clame that the paper wheel is some kind of majic sharpening device. I beleive it is the person that makes the difference. I just don't see how any sharpening device produces anything different unles the angle, grit size, and amount of passes on that grit is different. I've never used a paper wheel. However, I have used many different sharpening stones and systems.
 
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