Thanks for the interest.
I have designed the mill to cater to the scraping process, in that I can take advantage of the inherent accuracy of the process, without complicating my life with the things that a master scraping hand would find trivial, such as aligning “v” ways and the like.
The portion between the rail pads is milled to a depth of about 1mm. not to form an aligning edge but rather to reduce the area that needs to be scraped. The movement of the 3 axis are defined by flat planes. So in theory if one can produces perfectly flat planes the machine will be accurate. There are a few ways to do this, but hand scraping is so far the best that I have tried. One enterprising individual put a filler epoxy between the base of the machine and its rails and relied on the straightness of the rails and the solidity of the filled gaps between the base and the rails to form the plane. This wouldn’t have worked for me because the rails I purchased have a measurable instrument runout of about .01 inches. This is not acceptable for my machine. The other method that has been used is to put an epoxy putty on the machine base and place the base on a flat granite plate to replicate the flatness of the plate. I find this method acceptable but messy and it lacks the fine control of scraping. It is however much faster.
the alignment of the rail is accomplished in my case by scraping one edge of the 1 inch plate flat, then while bolting the rail on the pad, I will carefully tweak the rail until it is strait in both the x axis and z axis(which is defined by the scraped pad) if I find that there is too much deviation from strait in the z axis then I will scrape the bottom of the rail as needed until I get the straightness I desire or I give up and call it good. The other rail will be set parallel with gauge blocks to the aligned first rail. It will also be tweaked to be as straight as I can get it. I don’t have allot of time to devote to this project, so I can’t spend allot of time scraping the rails in. but I don’t think it will be all that necessary as everything looks like it’s going to go smooth.
The rest of the machine will be made out of aluminum too. I have some pencil drawing of it, I want to put it in cad, but I just don’t have time. The construction of the mill is very simple. You have a stationary table, which is also the primary structure of the machine, and then you have a gantry, made of cast aluminum, with 4 scraped surfaces all on the same plane. Two are for the right angle plates that hold the trucks for the rails on the bottom of the table. The other two are for the x axis rails. This is where the accuracy of the machine comes into play. The right angle plates will be hand scraped and will naturally be an accurate right angle. Since the two rail pads are scraped on the same plane it will be easy to maintain the accuracy on the project or at least it will make the tramming of the mill easier. I will have to upload some sketches.
Ray,
Life is a choice, death is choice poorly made.