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  1. #37

    Join Date
    Jun 2018
    Posts
    33

    Re: Horrible Surface Finish

    Quote Originally Posted by 109jb View Post
    As a test you can pull out the gib lock screws and replace with a bolt and a nut and adjust the gib as if it were a screw adjusted gib. This only gives you 2 adjusment points, but will tell you what you need to know. My G0704 has been running like that for years due to a tapered gib that doesn't fit right.
    Thanks for the tip. I'm doing something similar. I got rid of the original adjusting screws and made a spacer that fits the gib screw counterbore with just a few thou of clearance then use a socket head cap screw for adjusting. This gives me slightly better contact on the end of the gib.

  2. #38

    Join Date
    Jun 2018
    Posts
    33

    Re: Horrible Surface Finish

    Quote Originally Posted by pastaman View Post
    I'm trying to isolate the source of the deflection as suggested. For my own satisfaction, using a .0015" feeler gauge, I checked for gaps between the column ways and the head slide ways. I also checked for gaps between the dovetail ways on one side and between the dovetail ways and the gib on the other side. No gaps larger than .0015" anywhere.

    As I said in one of my previous posts I have .010" deflection with the DTI mounted on the table and the needle contacting the underside of the head next to the quill (see first picture). This setup is vertical so no deflection compounding. With the DTI mounted on the column ways and the needle touching the underside of the head next to the quill I get about .003" deflection (see second picture). The distance from the column ways to the needle contact point is 13". The last test I mounted the DTI on the Y axis bed ways with the needle touching the column ways just beneath the head slide (see third picture). I got .008" of deflection. This setup is virtually vertical so no compounding. These readings add up: .003"+.008"=.011". Close enough to .010" for me.

    The .003" deflection from the column to the head seems reasonable over a distance of 13". This tells me the clearance between the column and the head slide is not excessive. Now I need to look at the column mounting and see what's going on there.
    I isolated the column flex by putting a temporary spreader bar between the column and wall (see attached picture). This reduced the deflection to .002". I ran some profile passes and there was no change in the angular and radius portion of the cut surface. I would have thought by reducing column flex there would have been some change. I also changed the steps per as Jim suggested and no change in surface finish there either. I'm stumped.
    Attached Thumbnails Attached Thumbnails IMG_0839.jpg  

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