How does the angle unit for the guide rails work?

[Toller]

The protractor like thing that attaches to the guide rails; how exactly does it work? 

Is it long enough to hold a true angle?

 

[mhch]

  This question has been raised a  number of times.  Do a search on "angle unit"
  and you will find various opinions.  It looks to me that the average opinion is not excellent.

 

[Per Swenson]

You should look here.
http://www.woodshopdemos.com/fes-au-1.htm

Per

 

[Chris Hughes]

    There has been a lot of discussion about this accessory recently.  That being said, and as I have recently lent mine out and had to give a tutorial.lets review.  First, regarding accuracy; the tool I received was spot on, coupling this protractor with a rail will not diminish its accuracy.  Second, this application is not to "hold" a rail at an angle, but to "set" the angle in relation to the edge the protractor is set to.  This does not mean that this operation is meant for or with clamps.  As a rule regarding this unit, if you would use a clamp for the operation not using the angle unit then use a clamp with it.  Finally for me, I do not understand why someone would alter this adjustable unit to a fixed 90 degree.  It seems to me that there are much cheaper squares available.  Hope that helps, Chris

 

[Toller]

So it is a measuring device rather than a jig.
Thanks.

 

[Ned]

Toller--

Not a measuring device.  As Chris says, it is an aid to setting the rail accurately, but doesn't really fix the position of the rail.  The rail's own bottom strips fix the rail, or clamps.

When used as Chris describes, it works.  I have one but I don't use it very often at all.  The angle unit must be treated gently.  It appears that most people haven't been thrilled with it.  If all my Festools evaporated and I had to start again, the angle unit would be at the end of the list.

Ned