what angle to use for sharpening a cleaver

I sharpen a double bevel on mine.

Because yours is so old and blunt, you'll have to profile it on a coarse stone before sharpening.  Unless the cleaver is very thick indeed, sharpen it to around 22.5* by estimating a 45* angle then halving it.  This is the same angle at which you already probably sharpen most of your European knives.

Sharpen the knife symmetrically so that the bevel width is the same on both sides.  This will aid durability and make the knife easy to steel.  

Finally, after you are satisfied that your bevels are flat and even, and that the edge is reasonably good -- resharpen at around 30* just until you draw a burr on both sides and deburr.  A 30* cutting bevel (also called the "primary bevel" by most sharpeners) is sufficiently obtuse to hold up to a lot of abuse.  Meanwhile you don't want the edge too wide or it will wedge -- even being used as a cleaver.

You probably already know this, but it's worth syaing for the benefit of others who may be lurking.  A "meat cleaver" is not a "Chinese chopper."  They are used for different things, and one cannot perform very well as the other.

BDL

I edge and hone my heavy meat cleaver with an electric grinding stone then finish on regular stone.. My Chinese cleaver is done on wet stone.It really does not have to be razor sharp as a lot of its work is done by weight. Chinese cleaver on other hand should be razor sharp and is not for cutting through heavy bone.

Slight confusion here:
 

Quote:

Originally Posted by butzy 
This grinder is a heavy one and is dull, even for a cleaver. I actually have another one (same brand etc) that's a lot sharper (but also blunt compared to a chef's knife), so I want to get the blunt one up to at least that level.

I realise it's not going to be razor sharp.

The cleaver can be razor sharp if you wish -- that has nothing to do with the angle. Sharpness is simply a matter of how cleanly and consistently the two planes of the bevel meet. If the cleaver is sharpened to a 60-degree included angle (i.e. 30 degrees per side, as BDL suggests), and you do it perfectly cleanly, you have a razor-sharp edge. And ideally, that's exactly what you want, with every knife, no matter how it's profiled and no matter what the bevels are.

The thing is, the larger the included angle, the more durable the edge will be, and conversely the more the knife will act as a wedge to split rather than cutting the food. That wedging happens above the edge itself: it's a matter of where the shoulders are. A cleaver is used very brutally, and wedging is a pretty trivial concern, so you want a large included angle.