Joined rails will not lie flat

[rdr]

Lots of threads and discussions about joining rails on here but can't see one with the issue I keep hitting.

I can't seem to get my rails to join flat. Im using a long level as a guide and not tightening the screws overly but the rails just don't seem to join flat. They lie flat on their own but when joined its difficult to get the saw over the transition without jumping it over the join.

Any pointers would be very welcome. I'm beginning to think there is a problem with the extrusion making it skew as the joining bars slide in or am I missing something?

Heres a pic of my issue:

[attachimg=1]

 

[nclemmons]

I've had some flex in the past but no more than maybe a millimeter.

Are the rails butted together?  I typically leave about 1/16 to 1/8 inch between them.

You might try laying them on your table and tightening from the top first and seeing if the rail stays flat with one connector tight at the outside edge and then do the second one.

Have you tried 'flexing' them to get them into alignment?  There should be some give in the aluminum and you might find that helps.
I'd even consider clamping them on the back edge under a clamp on the table and pressing up or pulling down on them on the outside edge over the edge of the table to see if this helps them to align.

 

[DrD]

Looks like here's another one for the trainers.

Check the screw depth of the 4 screws on both the upper and under connectors.  Back all screws out until they are flush with the connector bar.  Then starting wherever screw you choose turn each screw on either the upper bar or the underneath bar a fixed number of turns, then go to the next screw, etc in turn.  Go back to the starting screw and repeat until connector is snug.  Repeat for the other connector.  This takes MUCH LONGER to explain than to do.

Maybe the trainers can ring in by Monday with their perspective.

 

[Holmz]

...
Have you tried 'flexing' them to get them into alignment?
...

Doing that on Skis and bicycle frames, they use the term 'truing' to describe bending them in straight alignment.

For the rails one would need a big fork to lever them torsionally. Which is what they also use for skis.

 

[ear3]

Does the same thing happen when you switch around the configuration (placing the rail at the back in the front)?

 

[rdr]

Hi Guys thanks for all the comments.

I get the same issue no matter which way i connect the two rails which is whats making me think its a issue with the extrusion. I'm away at the moment but will have a play when we get home tomorrow taking on board some of the comments above.

Thanks

 

[Rob-GB]

Just a thought and it may not be pertinent in your case.
How tight do you do up the grub screws on the joining bars as over tightening may cause issues.
Second thought, while I am thinking it over, is either or both rails in wind? you can check by using winding sticks to sight down the rail.
Paul Sellers has a couple of video's about making and using winding sticks

Rob