I bought a cheap hammer and wanted a nicer grip than the bare wood. Thinking of how nice a linen wrapped pool cue feels, I decided to try wrapping this handle in cotton string.

The only tools I used were a knife, a pair of scissors (but I should have used the knife!) and a bowl of water. The only material (aside from the hammer itself) was a length of cotton string and a short piece of nylon monofilament, which I did not even have to detach from the spool.

Step 1: Carve the Wrap Area

I carved notches at the edges of the area I planned to wrap, to give the string boundaries it wouldn't easily slide over. I measured by simply holding the handle and marking a half inch or so past where my hand went. I drew a careful line all the way around, at each end, with a ball-point.

I started carving using my little pocket knife but soon switched to a big K-Bar which went a lot faster. I considered carving away the top layer of the entire wrap area but decided this was not necessary. I carved only as deep as the thickness of the string, leaving a sharp cut at the ends of the wrap area and gradually smoothing the cut towards the middle of the wrap area.

I added a vertical notch at each end to tuck the string ends into so they would not disturb the surface of the wrap with an Unsightly Lump.

Step 2: Starting the Wrap

I wrapped the whole thing once to see how much string I would need. I cut that much plus buffer amount, and soaked it for a while. In general a natural fiber will stretch when wet and shrink as it dries, and I wanted the wrap as tight as I could get it. After a few minutes of soaking I wrung out the string and started wrapping. I began by putting 3/4" or so of the string along the vertical notch I'd made, and then made a right angle and started wrapping over it. I pulled tight as I went around and after two turns I did not have to hold the end any more. Every few turns I pushed the wraps together with my thumbnails. I wrapped up to the start of the second lengthwise notch at the handle's end.

Step 3: Finishing

While holding the string tight, I made a loop of nylon monofilament and laid it in the vertical notch, with the loop sticking towards the end of the handle. I then continued wrapping, over top of the monofilament loop, until I got as far as I could. The last turn took a little wiggling to get it into place, which is good as that meant it was nice and tight. I stuffed the end of the string through the monofilament loop and cut it short, leaving about an inch and a little of tail. I made sure the string had some give on both sides of the loop so it would pull through more easily. I pulled the monofilament ends out between the turns of the string and the string end was buried under the earlier wraps. It took a bit of a yank to accomplish this. Finally I cut the string end off - I had to recut it with a knife because scissors were too thick to get a really close trim, dunno why I didn't just use the knife at first.
This is a bit of an experiment. If after use it turns out to be a cautionary tale rather than something to emulate, I will post that later on.