Old Mech

Good Morning Gentlemen- Wow. You guys ARE good. Here is an update: The table is anchored to an 18" slab that has a lot of steel in it. Rebar, not netting. This slab is 24' x 24', and is isolated from the rest of the flooring and the building. This slab is also attached to six 30' Deep Pylons screwed into the ground and filled with concrete. The specs left by the installer show that the original tolerance was .0003" Flatness. I did not get that good this time. It is, in fact, very similar to Jello. I found that criss-crossing was better than circular, although I have not yet decided on a pattern. I ended up getting the table in rough (+/-.010), and then I went at it piece by piece. I tweaked the corners, and then the middle, and then criss-crossed all over the place, checking, checking, checking. If I moved an anchor, say, .002, I found that sometimes the one next to it would move, and sometimes it would like skip over to another row. So, by very carefully and slowly tweaking the worst of the worst, I gradually got the dang thing within +/-.003 from one end to the other. I shall now write up a MAP and detail my work so that next time I can jump in and kick right off. I will also order some better tools. I also found out that the lazer had to be checked constantly, because the base would sometimes go off; so I checked the levels on the Laser every time I walked by it. Then I found out that the fan I was using was also playing havoc with the readouts, so I had to make sure I had a nice coating of oil on the table to resist the sweat dripping off my nose. :D Thanks alot to all of you, your suggestions were more than worth the time.

Awesome job, there. You have inspired me to start work on my book hinge project.

Thank you DSW. While I do not know the exact construction of the floor, I do know that 100 years ago it was swamp. I will try your test and keep water and soil in mind. I will also try and find out more about how much concrete there is.

Greetings- I have a small quandry. I am setting up a cast iton t-slot set-up table in the shop. It is 4 tables bolted and keyed, ground flat, 12' by 19', set into the floor with 72 anchors, into a slab that is joined to 6 30' deep pilons into the ground. Heavy stuff. I am in the process of truing and leveling this table using a Hammar Laser Level. This table had been re-worked several years ago, and set up in its present position by an installer. After several people have re-leveled it, and about a year since its last check, it has gone a bit out of whack. We use it to set up machine frames for building to get them as true as we can before moving them to the construction bay. I have been assigned to make it perfect. I think that is because I am now one of the "old guys" who know all the secrets. (I don't know everything) Problem is, there are no other "old guys" around to ask. When I got to the job, there was an overall .010 sag in the center. I loosened up all the anchors and let the baby float and relax. Then I shot all 4 corners, got an average, and set them all to a common zero. Then I started in the center, brought it up to level, and began setting the anchors in a circular pattern to keep things evened out. When I got done, the center was .005 high. I put it down, and the next row went up. It started to act like a bowl of jello, so I just left it set for the weekend. What I would like to know is: Is there a preferred pattern to setting the anchors to 0 so that I do not end up chasing around in circles? Should I have gone diagonally and criss-crossed over the center instead of a circle? How can this much iron move around that much? I am familar with leveling machines and using the tools (30+y), but this is a mystery to me. A good answer or a link to material to find out would be so kind.