LR32 First time - accuracy acceptable or bad setup?

[Scorpion]

So I'm calibrated and set up like Erock recommends - board length is divisible by 32mm (1216mm) and I've got both end stops 16mm up and out. 

Conceptually I should be able to in-set the side stops to 37mm drill the holes like this -

flip the rail to the other end/end stop, re-align the side stops to the other edge and go to town.

However, when I do, the holes on the second pass are 1.5mm lower than the first side.  After checking the first hole I then reset the rail assuming I didn't have the second stop up against the material however it actually was. 

The board was cut on the Kapex so the cut is 90-degrees.  Checked anyway using my straightest straight edge and it's perfectly straight (thank you Kapex).

So I'm trying to wrap my head around this.  Shouldn't have issues flipping the rail end for end.  The stops are (reasonably) identical (I'm a machinist so I accept woodworkers slop).  1.5mm sucks - it'll give every shelf the teeter-totter when on pins.  I feel like what I'm trying should just work.

Is that (in)accuracy normal or do I have something setup incorrectly?

 

[Bohdan]

When you say that you are calibrated did you also centre the cutter in the router hole in the LR32 plate?

By the way which router are you using?

 

[Bohdan]

I would also mention that the divisible by 32 method only works if your lengths are exact. A 3/4 mm error in length would give you a 1.5 mm variation in the hole positions.

That is why I always work off the same edge (top or bottom of all pieces) and prefer to move my stops rather than flip the rail - much easier to get accuracy and my holes are spot on.

 

[Scorpion]

When you say that you are calibrated did you also centre the cutter in the router hole in the LR32 plate?

By the way which router are you using?

After posting I went back to mess with it.  You nailed it (shoulda sat on the couch with a cold drink in hand waiting for your reply instead...lol).  I walked through the setup and found that the router/sled flips 180-degrees when I invert the rail.  If the bit were not centered (well) the hole would be off twice the distance off center in that orientation as well as offset from the edge after the flip.  In my case the bit was under a mm offset - the 1010 must have budged a hair when I tightened the holding screws.  After re-centering and re-testing, the holes are D.O.B.A. (dead on balls accurate). 

So my lesson today is - test cut before I go to town after initial setup.

Thanks!

 

[Scorpion]

I would also mention that the divisible by 32 method only works if your lengths are exact. A 3/4 mm error in length would give you a 1.5 mm variation in the hole positions.

I flipped over the rail and checked the measurement between stops.  It's exactly 1mm narrower than it should be making the fixture itself not divisible by 32mm.

That is why I always work off the same edge (top or bottom of all pieces) and prefer to move my stops rather than flip the rail - much easier to get accuracy and my holes are spot on.

I actually started working off of one of the ends because that made sense to me out of the box.  I only shortened the board as I followed along erocks video trying to figure out where I went wrong.  Knowing now that the stops themselves aren't divisible by 32mm will force me back to using the same reference edge.  No biggie though, the cabinet I'm building at the moment is already too tall for my holy rail.