I usually hold the khukuri facing up, point away from me.
Then hold chakma with index finger out 3/4 of the way on the chakma itself so I can apply needed pressure(widest side of Chakma down on edge).
Keep the khuk (point away from me) facing edge up, then turn edge to the left 45degrees(or the angle you would steel it at)and run the chakma down the whole length of edge. (However for very dull edges, esp. ones with rough spots, Bruise is right. You often can put alot of pressure in small stroke increments as you go. But remember you'll have to align the edge to match those parts you work over extra hard)
Now, depending on a few factors, you'll be doing it differently. If you have a good HARD chakma your life will be easier. If the chakma seems to be really soft and won't really even raise a burr on the softest parts of khuk (right near cho and farthest part of tip)then you're better off finding a harder chak. from another khuk(I have one from my 20"AK that I always use cause its really hard, and huge!)or using a smooth steel.
Now, start on one side and as Yvsa taught me, I work one side completely with strokes going all the way from cho to tip (until thre is burr running whole length of edge). Sometimes(often)you'll find that you need to apply more pressure within the course of the stroke when you hit the sweet spot. SO you stroke goes like this pressure wise "normal pressure--hard pressure--normal P.". Then when you have an evenly rough edge in one direction(burr) turn it over and do the other side.
I let off pressure as I go and the khuk becomes sharper. It is possible to do fine sharpening work with the chakma. I often just let the weight of the chakma rest along the edge for the final touches. I have been able to bring a chopping dulled khuk back to semi-shave sharp this way. And its very possible to bring them to shaving sharp if they aren't dulled badly to start with.
Once you get the hang of using the chakma I bet you'll find yourself reaching for one to put edges back on other knives as well
The nice thing about the chakma for me when I started out sharpening these knives, is that it is much more forgiving of mistakes than a course diamond steel or stone.
Enjoy!
