This thread started by Hector, but I added Kobus's experience above . . .

. . . . . . When I bought the 60x60 angle iron I asked for STRAIGHT pieces. When I looked at them at the yard they looked straight, but at home I noticed that they are not 100%. Will I be able to get them in line when I bolt them onto the gantry and the X axis one onto the table?

Gerald, if you think that the angle iron cannot be forced into position I can buy a new piece and use these parts for the legs of the big table.

I can't judge how bad your angle irons are for line. All I can say is that they are surprisingly easy to coax into line with the shims and the screws at close intervals. What is the biggest kink you have over 500mm? I would guess that 2mm over 500mm can be tolerated?

Found the SA Institute of Steel Construction spec: "The straightness of any length shall be such that the offset does not exceed 1/500th of that length". So you should be at 1mm per 500mm, which I think would be easy to screw down straight.

Thanks Gerald, They are not that bad. When I put them back to back next to each other, there is a slight gap in the middle. I can press this GAP close with my bare hands.

Just check me on this one. The Y-rail clamp strip holes will be tapped to 8mm. The gantry holes are 9mm and the angle iron rail holes will be 12mm. Is the 12mm holes in the rails for adjustment / straightning of the rails ?

I have my spacing at 160mm apart.

Yes, the extra gap is for adjustment.

This weekend i mounted the X-Rails on the table. When I started I thought I will NEVER get it right. The rails were as crooked as a railway line after a massive earth quake. I measured out the width of the gantry, then started with the first rail. I drilled hole for hole, making sure I get it even and straight on the main beam. I then put the gantry on and ran the gantry inch for inch and lined up the second rail drilling hole for hole. The end result is a gantry running as smooth as baby snot on the rails....I am very, very impressed.

Rails are bended...What alternatives I have...??? :(
 

:Just finished cutting to size x and y rails...started to grind but stoped in the way after realizing problems ahead :(.

X Rails...
They present bending, both have about 1/8" of deflection in the center in th Y direction, both bends are towards the inside of the angle, this makes me ask several questions...

The oversize holes (1/2") in the x rails are used to aline the rails parralel. This oversize holes give us a play that permits the rail to bended in place, tigthening the bolts will set the rail straight, will the bolts hold the rail straight in place?

Y Rails...
They also present bending, about 1/16" to 1/8" of deflection in the center in the X direction, one bends towards the outside of the angle and another to the inside. I managed to correct the one that bend toward the outside with small welds on the outside...But the one that bends to the inside is to difficult to correct, I throw in lots of welds and it was useless...

Other questions....
1.If I correct the bends before cutting the angle side to 28mm will the rail stay straight after cutting it?
2. Will straight angles from factory stay straight after cutting them?

The rails will bend after cutting. It is what we call a "slow" or "even" bend - it does not have "sharp" bends in spots.

A "slow" bend is easily corrected by hand, just using the flex of the rail. The bolts will hold the rail straight. That is why there are so many bolts. That is true for both the Y and the X axis.

Some short welds are a bad thing on the rails because they will make "sharp" bends in those spots.

I have added some posts by Kobus to the top of this thread.

I was overconfident of trying to correct the bends of the Y rails...they are spoiled :mad:, no problem...:rolleyes: guess Illhave to start over again with those rails. Just one doubt. I used a jig to mark the holes for the cross bearers on the main beams, they turned with very good alignment. my question is maybe its better to mark this way the holes on the rails, because if I use the clamp strip as a jig I´ll be transfering a straight line to a bended rail (thinking that the clamp strip is straight), instead if I use a jig with a fence located 46mm apart from the edge and with holes with the correct bolt separtation I will be following the bend of the rail, and when it comes to the alignment Ill have more clereance in the holes for parralelism in the rails and of course for correcting the beam...

OK...it came to me why not to do the jig thing ...In the X rails it can be done that way just rail and beam to bolt no problem beacuse the beam is the taped element, but in the Y rails is a different story, a thirth memeber is added, the clamp strip, and If I dont use the clamp as jig at the time of geeting the rails+beam+clamp strip together it will be a nightmare...
is it correct my logic?

Logic is correct, but flex the clamp strip to be parallel to the rail at 46mm.

Its a good idea to double check the channels and angles when purchasing them...I order mine and received them without checking them througly...poor quality in my steel has made me loose time and money...today I went an purchase another strips of angle to made new Y rails after spoiling the first ones, I was meticilous about strait angles...after cutting them they turned pretty straight...