3 Attachment(s)
What I used to tell if my rails were straight side to side
Earlier when I had adjusted/set-up my Shopbot, I used an 8 foot long level,,, but my rails are 14 feet long..... so I had to do some approximating and guessing. A few days ago, as I prepared to re-align my machine, it occured to me that I could do something different, and better (I hope) which would allow me to more accurately measure side to side variations in my X rails, and not require the use of my level.
I used two framing square stops, which are used in making repeated right angle cuts. These stops are cheap, from any big box hardware store, and are shown in the first picture. http://www.talkshopbot.com/forum/att...id=31848&stc=1
I used .003" diameter copper wire (all I had that was so fine, but it worked well enough and would draw tight and straight without breaking), which I attached under the knurled nut/set screw of the brass stop. I then clamped the brass stop to one end of my X rail. http://www.talkshopbot.com/forum/att...id=31849&stc=1
I then pulled the other end of the wire, down to the other end of the same X rail, attached that end of the fine copper wire under the head of the other brass stop, drew it tight, and clamped it to the end of the X rail. Then, using a scale, as shown in the last picture, was was able to accurately measure how far the X rail was from the wire at any point of the rail. http://www.talkshopbot.com/forum/att...id=31850&stc=1
And because I could put the scale right up close under the wire, I didn't even have to worry about paralax error when making my readings. I started off using the 1/32" - 1/64" side of the scale, but found it easier to use the 1/16th inch side.
Also, while this was not a super taught steel wire, any sag in the wire (which was not readily visible) was in the downward direction, and would not affect the distance from the vertical surface of the X rail. IF I had such a fine steel wire, I could have drawn it taught, and probably have been able to use it to measure the top edge of the rail for straightness. But since as I understand it, getting the rails parallel is most important, this seems to be a useful method..... Though I probably re-invented wheel at best, it should still be useful.
Thanks, Chuck