So with a decent reference point I was able to start work on scraping - a week later than planned
![:bugeye:](https://madmodder.net/Smileys/default/confused0068.gif)
Connely talks about getting the face of the column flat and perpendicular as the first step. On the Centec though the column face isn't a load bearing surface as the knee runs purely on the ways.
So next step in the process is to get the "guiding way" (opposite side to the gib way) flat and square. To do this I used a combination of a dial indicator mounted in the arbour and a longs straight(ish) edge. The straight edge allows you to measure deviation as you swing the DTI in the arbour. Pic 1 shows the setup if you were using it to check the face, but I just used it in the way. Also had the arbour (Jacobs huck
![:bugeye:](https://madmodder.net/Smileys/default/confused0068.gif)
) clocked with a seperate DTI to keep an eye on errors there.
Rather strangely to my thinking the bottom of the face is further out from the chuck than the top, this is true on both side and is about a .12 - .14mm difference. I could understand the bottom being deliberately "proud" to combat sag when built up but 5-6 thou seems a lot. Also I expected the bottom to be most work but it is actually the middle that was showing more wear.
After a rather abortive effort (see post in "scraping lessons learnt") I eventually got the way pretty flat. I am using a combination of a dovetail straight edge kindly lent to me by Julian (but this only covers 3/4 of the knee) and a prism kindly lent by Pete (which covers the whole knee but is very heavy and difficult to balance on the way). As a result my work method was to mainly use the small edge to get the bottom 2/3rds of the way flat up and down and outside to inside edge and then check the overall flatness with the prism. the top 1/3 of the way isn't actually used on this mill as the knee never goes that far so I wasn't too concerned with this part.
After the first attempt it looked like pic 3 and the gradually worked it in via pic 4 till we ended up with pic 5. It is about 15 - 20 PPI across 60% of the main bearing surface and that is good enough I think. The "incline" on the column is now .06mm (3 thou) top to bottom i.e. the base of the way is .06mm proud of the top measured relative to the spindle.
So that's way 1 done only another 15 surfaces to go
![:doh:](https://madmodder.net/Smileys/default/doh-45.gif)
- might wait till next year to do those
![:)](https://madmodder.net/Smileys/default/side2side.gif)
Cheers,
Paul.