First, fun stuff.  I cut this on my smaller mill.  In the end, the top was pink with black lettering.  The best way that I found to paint it was by machining it first, then priming it liberally.  After the primer dried, I liberally dabbed black ink into the lettering (at .1” depth) and sponged the excess paint from the top.  After the paint dried, I used a roller to roll a couple coats of pink over the top.  I wasn’t smart enough to take a picture of the final plaque, but it turned out really well.  It’s about 6” wide, and I cut it with a 1/16 endmill.  The material is oak, although pine seemed to work just as well.

The big excitement for me this week has been putting those finishing touches on my new mill.  Part of what’s left to be done it to check accuracy and make alterations where necessary.  This requires a dial indicator.  These buggers are interesting, if you’ve never played with one.  The travel on them varies with accuracy.  If you want more precision, you get less travel.  The one I bought was only $25, so it probably isn’t terribly accurate.  You can see it in the picture below.

As I started testing accuracy on the Y axis, I noticed that when I programmed 1”, I was actually getting a lot less.  The error seemed consistent, though, so I bumped up the number of steps per inch.  That worked just fine, except that I got different results for long and short distances.  For a bit, I started to wonder if there was something wrong with my cheap dial indicator.  When I was nearly about to give up, my friend G-Smack GC happened to call.  While we were chatting, he suggested that I should verify that the results were consistent if I traveled 1/10” at a time.  The first 1/10 worked fine.  The second, third, fourth, and fifth 1/10 increments were each over by the same amount.

Can you spot the problem?  Last night, based on the results of distance travel to 9/10”, I thought the machine had very little Y axis backlash.  I was wrong, though.  It actually has quite a bit (0.0075”).  Since I was moving consistently back and forth, the backlash was self-compensating.  Once I programmed Mach to compensate for backlash, and reset the steps per inch to the base number, I started getting very consistent travel.  The dial indicator showed that travel might be over or under by 1/1000”, but I think that might actually be the indicator.  The X axis backlash was even worse, at 0.014”.  That, I believe is caused by a loose thrust bearing.  When I get paid again, I’ll probably spring for a set of Heli Cal zero backlash couplers.  Fortunately, as long as the backlash is consistent, Mach does a great job compensating.  If I get really crazy, I might also buy some better ball nuts later on too.

The following video is just a quick demo of using the indicator on the mill.  The numbers you see are thousandths of an inch.  You can see the needle start on 0, travel 1/4”, and then return solidly back to 0.

I’m curious what I’ll find when I put the indicator on my MaxNC mill.  It uses solid couplers (no backlash) and leadscrews (very, very little backlash vs cheap ballscrews).  My guess is that the machine has almost no backlash, but does need to have steps per inch tweaked a bit.