Cutting Metal Again

The continuing story of the problems with my small milling machine losing motion came to a happy conclusion this afternoon, and I was able to complete the cuts for oil grooves that I was setting up to make when I discovered the problem.

This is the last pass on the last oil groove.  Groovy, huh?

So what was the fix?  Did you think I'd let you get away without telling you?  First off, let me just show you the parts cross section again. 

As I said in the most recent piece, I just wanted to replace the coupler, pre-load nut and 5-40 screw.  That's basically everything except the leadscrew and the Sherline motor mount with its two sets of ball bearings.  I rebuilt this on Tuesday using blue LocTite on the taper of the leadscrew and set it aside for a few hours (which ended up being Wednesday morning).  On Wednesday, I started slowly moving the X-axis and all was fine.  I had written a simple G-code file to exercise the X-axis, moving it from -4.0 inches to +4.0 inches and back several times.  The table stopped moving in less than five minutes.  

I took it apart, of course, and found that the LocTite had sheared.  All I did was just reassemble it with LocTite on everything.  I put a light smear on the taper, a small drop on the 5-40 screw and another drop on the 1/4-20 threaded lead-in threads on the leadscrew.  Then I went to LocTite's website to look up just how long it should take to cure, and found a data sheet.  The answer was that it really takes 24 hours to get to full strength.  So I said I'll leave it until 24 hours is up, Thursday around noon.  Again, I started slowly and moved the X-axis back and forth for a while, then ran my short exercise file.  This time it worked.  Then I ran an extended version, which took about 45 minutes.  All in all, I ran it for over an hour with no issues.   After an hour of doing things it wasn't capable of doing at all a few days ago, how long does it take to get confidence it can keep moving?  Put it this way: if one of those parts had snapped in two, would this even be a question?  There would be a broken part and a new, unbroken part, and the only question would be whether it was put back together properly.  

Thursday night and Friday featured Christmas parties, so I didn't get back to it until today.  This time, instead of my X-axis torture test, I wrote a little exercise routine for the mill to run all three axes simultaneously for a half hour.  Everything held together just fine, so I moved the Grizzly's cross slide back onto the little mill's table, zeroed the coordinates to match the drawing, and then proceeded to cut the slide.   It did hiccup, the table started shaking too much.  It turned out that when I put the X-axis gib strip back in, I didn't seat it properly.  That didn't show up with the X-axis not carrying the 10 pounds of cast iron.  Once I shut everything down and reassembled that last detail properly, everything was fine. 

Now it's on to drilling the 1/8" diameter, 4" deep hole.