I got a screwfix catalogue last week that offered some levels by Forge
Steel. They have a self levelling one for £37 49 and a Rotary one for
the same price. Yet the bumph says that they are both self levelling.
Both are class II whatever that means, the first has a 10 m range
whilst the rotary has a 30 m range. So what are the likely differences
A slight difference being that if you were transferring a level a long
distance with a conventional level, then you would (well should!)
reverse it each time you extend the level - that way you reverse out any
error each time. With a laser level you would not do this, so the base
accuracy needs to be better really.
The spec. in the booklet is 0.15 degrees per metre. That isn't a great
deal of inaccuracy.With the rotary one the range is 30 metres so the
inaccuracy -if it remains at 0.15 degrees per metre over the full
range, is 4.5 degrees.
But if I had to ever use it on a 60 metre room I should feel entitled
to ask my employer to hire an expensive one. Also at that range the
two end readings would be the same error and the same level.
Moving the laser to the mid points, between the centre of the building
and its two ends, would allow me to take the correct reading from the
centre of the building and correct each end reading in turn.
At 40 quid that's not a bad bargain. I think that hiring a good one
for a day costs more than that.
|!>> Lurch wrote:|!>> >>>http://www.screwfix.com/search.do ;jsessionid=GQZRDX4X0CABOCSTHZOCFEY?...|!>> >> If you load the instruction manual for the rotary the accuracy which|!>> >> is quoted in +/- mm per m is 1 which seems an awful lot. At 5m you are|!>> >> going to be 5 mm out (possibly)
|!>> > Most fixed levels are accurate to around 1mm in 1000mm so not really|!>> > any different.
|!>> A slight difference being that if you were transferring a level a long|!>> distance with a conventional level, then you would (well should!)|!>> reverse it each time you extend the level - that way you reverse out any|!>> error each time. With a laser level you would not do this, so the base|!>> accuracy needs to be better really.|!> |!> The spec. in the booklet is 0.15 degrees per metre. That isn't a great|!> deal of inaccuracy.With the rotary one the range is 30 metres so the|!> inaccuracy -if it remains at 0.15 degrees per metre over the full|!> range, is 4.5 degrees.
|!Except in the very largest of rooms, the beam does not curve.
All beams curve *a little* even when the load is only the weight of the
beam itself. This may be very little, indeed not measurable with DIY
There are two sorts: line generators and flying spot rotaries.
Line generators have a lens system that projects a line. Usually it has
two of them, at right angles. Rotaries have a single whirling mirror
that projects a single spot quickly enough to look constant. For much
more money you can also find twin spot rotaries.
They're both self levelling, owing to a pendulum. Usually line
generators are much more accomodating of tilt.
Both have an apparent brightness that varies with the angle of the
surface they shine on, so the "centre" of the projected line is usually
brightest and it tails off to the sides. The line generators are also
significantly brighter in the centre of the line, so their side
performance is relatively poor. Spot brightness is effectively
independent of range, until its diameter gets bigger -- it's the side
slant direction that limits their use, not the straight-on spot.
So for indoor use, such as tiling, get a line generator. They're cheap
For other uses, you ought to get a rotary, but you can't afford it
(still £200+). Cheapie rotaries are neither one thing nor the other.
The tripods are all far too short and basically worthless. You need an
adapter (cheap from a camera shop) to use them on a photographic
Thanks for all that Andrew.
I can afford but would seldom use a £200 level. I might get a line
generator one day. But for getting door frames all on the same level I
just use a block of wood on the floor.(Unless I am following obvious
It's just that with the modern insulated floors that are getting
specified these days, it might be an idea. As I work on sites, it
doesn't approach my requirements that I supply any such a thing.
I've only needed to use one once and the firm hired it. It was rather
expensive to hire one. If I was doing a lot of studding it would be a
It is interesting to learn what these things do though, as to a layman
they all seem much of a muchness.
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