The Juuma rebating block plane arrived this morning - I diverted into checking it out and setting it up as it seemed as though it would be a good idea to share some findings while this thread was still live.
Bear in mind that the following pertains to the specific Juuma/Fine Tools example, and that there could (?) be quality differences between the various Quangsheng/Luban and related brands. It from a manufacturing point of view seems in summary to be spot on and very good value for money indeed.
The small size perhaps helps, but the sole and sides when checked with an engineering straight edge and square are nicely ground, flat and square to each other. Backlighting saw no visible light come through under the straight edge resting on the sole - see the pic. of the test taken with the iron installed and the cap tensioned.
The bed for the iron is milled but in practice is smooth enough to not catch a fingernail - and with the rear support (which the adjuster passes through) is very accurately aligned with the sole. It's also very flat - see the pic showing how the film of marking blue on a gauge block transferred all over it.
Both the iron and a spare bought with the plane are nicely ground and finished - the bevel is ground dead on square, the sides are parallel and the back flat. Both measured 44.40mm wide x 3.1 thick - for an overhang of 0.1mm. (0.004in total = 0.002in on each side of the body when centred)
The backs flattened in a few minutes on a 1,000 grit waterstone with no need for ruler tricks etc. - which left them ready for finishing on finer stones. (see pic)
The surface finish on a Veritas iron is in comparison a bit finer. (is lapped?) The task in prepping these ones is to polish out the (fine) texture left by surface grinding - which took a shade longer than did the Veritas irons I've done.
The steel is listed as T10 carbon tool steel - it at first touch on a waterstone feels much like say O1. Time will tell how it does.
The (fixed) mouth as the iron just starts to emerge is around 0.7mm wide - quite tight but probably appropriate on a tool not designed to take heavy cuts. It's nice and square and the cutting edge when the iron is centred ends up parallel to the sole.
Having got the engineer's blue out I thought for the hell of it that I'd test the various surfaces of the body on a surface plate - see the later pics with blue on the various surfaces.
A fine film of blue is wiped on to the plate, and the relevant surface of the plane body is pressed down on to it - so that blue transfers where it contacts the plate. Blue all over means the surface is pretty much dead flat, misses mean an (in this case a very slight) hollow.
Bear in mind that this is an impractical/extreme test in that it'll pick up an out of flatness of a few 1/10ths of a thou (say 0.0004in) - much less than matters in use.
The sides proved to be dead flat. The sole almost so with a tiny hollowing towards the centre which could not be detected with straight edge and 0.0015in ( 1 1/2 thou) feeeler gauge or using a backlight as above.
Tightening the cap iron using the bronze wheel incidentally (but as is to be expected) produced a detectable increase in the hollow. The first pic of the sole with blue on is with no iron fitted, the second with the iron fitted and the lever cap tensioned.
All in all I'm very pleased. Just about the only (very minor) criticism I can make is to say that the polished dome of the bronze lever cap as delivered with a thick lower edge made access to the wheel a little fiddly.
This was easily resolved by setting the wheel lower on its threaded stud (to raise the back of the cap a few mm) and chamfering the relevant lower edges of the dome - see the last pic. A dragging/slight binding of the M6 wheel stud thread in the cap was fixed by running a plug tap in to bottom - perhaps the production tap was a little worn.
The nose of the bronze cap was making good contact all along its leading edge as delivered and would have worked fine, but since I was in the vicinity I used a diamond plate to give it a finer finish.
I couldn't be more pleased with the plane.
It's as before possible with a light mill to fit circular nickers (available as spares for a Veritas wheel gauge) a la LN and also a pair or even four Veritas style iron side to side locating grub screws (as on their shoulder planes) but mindful of the advice regarding use of a knife have no plans to do so unless the need arises in practice...