Sorry for the double post!
Here is an image of the bits of metal, after 2 days in cola and a hard scrub with a wire brush.



Much cleaner and I will give them a quick going over with the angle grinder and a grinding disc as well.

Hi Tom.,Never mind the grinding disc, get yourself a knotted wire wheel for the angle grinder, but be sure to secure the workpieces when using it, and wear eye protection and a leather apron, the wires can shed like darts, and will penetrate you.

They are better if you can fit a speed controller to reduce the rpm, ensure the grinder and wheels etc are compatible.

I got myself a wire brush, for my drill and it seems to polish them up a little, but not get the last remains of the rust off.
The surfaces of the hammer head and the ball peen and cross peens are less than perfectly flat, so I used the angle grinder with a grinding disc on and really lightly went over the top of the flat head of one of the hammers and it produced a perfectly flat end.

Obviously I can't do this with the ball peen ends, as it will change the shape of the end, even if only a little.
Going to try and give them a good going over with some rough sandpaper. Once i've got all the ends cleaned and polished up, I will paint the hammer heads with my hammerite paint. Then I only need to fit them to the handles.
I've got a friend giving me some hardwood tonight, so I can make the wedges.

John is right in suggesting a knotted wire brush for the grinder, a soak of vinegar and a wash off and grind will sort it out.

They are tricky beast so start carefully, i did a foolish thing a few days ago and thought i would just tidy a fraction of leftover scale on a 180mm piece of 40x3mm steel freehand. I now have a very red and sore scab on my ribcage. Could have been much worse.

I've found that the grinding disc, gives a lovely flat head, without removing too much material at all.
I had a go at the ball peen end, with some sandpaper and a load of elbow grease and its cleaned up ok.

I've also sanded down the handles now, as well. Tonight I will carry on cleaning up the handles and may get time to make some wedges from some hardwood my friend is giving me.

How would you all treat the hammer handles, once they have the hammerhead attached?
I was thinking of oiling them with linseed oil, but not sure about varnishing them. Don't want them to slip out of my hand.

For blacksmithing you generally DON'T want the faces perfectly flat but with a slight curve---a "rocker" curve for them. The first thing we generally have to do when buying a new hammer is to dress it away from flat to the curve we like. The nice thing about used hammers is that you can often find them pre-curved and so save a step.

For treating the finished hammer handle , use sweat , lots of sweat and water from the slack tub. Oils and varnishes make a slippy grip, and not what you need.

I thought i'd just linseed oil the handles, with 3 thin coats, to help them stay in one piece. No varnish or anything!
Should stay unslippy and also last a while.
I've recently got the hammerheads painted and yesterday bought a spokeshave to shape the handles. Just got to get the time to get it done!

In one of the blue prints here it was suggested to use mineral oil on the handle instead of linseed I tried this and like it better than the linseed it is also a bit cheaper

Here's how I do it.

John is right in suggesting a knotted wire brush for the grinder, a soak of vinegar and a wash off and grind will sort it out. They are tricky beast so start carefully, i did a foolish thing a few days ago and thought i would just tidy a fraction of leftover scale on a 180mm piece of 40x3mm steel freehand. I now have a very red and sore scab on my ribcage. Could have been much worse.

Could you dumb that down and explain it? Is that some kinda steel you can't hammer or something?