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I received an email from Ian asking if I had measured the X Y axis accuracy on my milling machine. The issue he had found was that the X and Y axes were not at 90° to each other and that over a distance of 100mm were out by 0.4mm
I have included some of Ian′s descriptions of how to measure this along with photos I took when measuring my machine and some numbers that Ian has collated so far for different machines. If anybody else has any measurements or comments then please send them in to me and I will try to expand this article email@example.com.
Firstly fix a dial gauge to the mill column (not the head, but the column itself so that rules out any head issues). I did this using a magnetic base.
Then I stuck a vice on the table and on top of this clamped an engineers square. The vice was really just there as a block to lift the square off the table so that the dial gauge would clear. I then moved the engineers square and kept traversing the face until the needle on the dial gauge just did not move. At this point I had the base of the square exactly parallel with the X axis.
I then moved the dial gauge through 90° and very carefully aligned the dial gauge with the narrower edge of the square. I then traversed the dial gauge along this edge a distance of 4 inches (sorry, but my dial gauge is imperial so decided to do the distance measurement in imperial as well.
The error in the dial gauge over the 4 inch distance was 4 thousandth′s of an inch. This equates to 0.1mm in 100mm.
The results that Ian has from the internet along with his and my Amadeal XJ12-300 are as follows:
So what does this mean, well, again thanks to Ian some comments from him on the issues:
"With the error I have I can see it in evidence when checking two faces of a metal block for being perpendicular by using the inside of the engineering square and holding it up to the light. It depends on what you are going to be making of course, but when trying to get holes to line up in two different pieces 0.1mm can be quite a large error. Imagine you machine two identical blocks, both at the same time, drilling a hole 100mm in referenced from the center of the rear edges. If you then put these two blocks together (e.g. to bolt them to each other) with one flipped over on the top of the other your holes won't line up by 0.2mm. In my case it would be 0.8mm - no chance if the holes were for a M3!"
We have recently reviewed the Amadeal XJ12-300 milling machine which prompted these checks.
See also: Tools & Tool Reviews.