One of my sets of beater chisels has been on "indefinite loan" for a while now, and the previous firmer chisel thread piqued my curiosity, so I picked up a set of the Narex firmers to replace them. Some observations:
- The sides aren't parallel. They're bevelled at about 4 deg/side, which means that the chisel is about 1 - cos(4) = 0.24% narrower when registered via a side than when registered via the back. For me this is insignificant (I have dedicated chisels with much less side taper for mortising) but for some it may be a deal breaker. Don't buy these if you're expecting a parallel-sided sash mortise pattern chisel.
- They're slightly tapered from edge to neck, which makes them a nice complement to my existing collection of constant-width chisels. For example the "26 mm" chisel is 26.0 mm wide at the edge and 25.0 mm wide just before the neck.
- Like all Narex chisels they appear not to have been post-machined after hardening/tempering, so their backs aren't as flat as some others. The worst example in my set was the 20 mm chisel, which was bellied and had a small amount of twist. Even that one only took 15 min or so to flatten the first ~2.5", which included knocking down the worst of the bellying, using 60 um diamond paste on a mild steel plate.
- Balance, ergonomics, edge refinement, edge life, etc seem about the same as the Narex bench chisels. I like the hoopless boxwood handle design in these more than the hooped beech handle in my Narex bench chisels (though note that you can also get bevel-edge bench chisels with the boxwood handle).
My bottom line is that I think they're great for the price provided you know how to quickly and efficiently flatten them, but perhaps not what some of the more "traditionalist" people here would ideally want.