When last we heard from our hero, I, er, he was bellyaching about his lousy day…

First thing this morning, I awoke to find an email from CNC Fusion (where I bought the kit) explaining how to repack the errant bearings for the ballscrew.  That’s a good thing, because the other advice I found was quite involved.  Despite their lack of formal documentation, CNC fusion has done a good job responding to my questions.

Whilst actually following their advice, I ran into the inescapable truth.  My workshop was a mess.  From the time that the new mill arrived until today (it’s been about three weeks), I have never gotten things organized.  One of the ball bearings bounced off the bench and into oblivion.  I could no longer call my workshop anything other than a “sty”…so most of today was spent finishing my newest bench, taking out the trash, and getting things back in order.  It isn’t finished, but it’s definitely much, much closer.  The bench is done, the floor is clear, and the parts and tools are organized. 

That doesn’t do much to advance my promise for a “CNC Week”, though.  Not to back out of my promise to work on CNC projects this week, I come “bearing” updates.  The first is that I’ve created a new video on how to repack bearings. 

For the second update, let’s consider for a moment how these bearings came out in the first place.  I ran past the end of the Y axis.  What prevents this from happening during normal operation?  On the stock machine, a washer on the end of the ACME screw stops the table at the end of travel.  No such washer comes with the CNC Fusion kit.  Chew on that for just a few moments.  If, at any time, I were to forget to reset the machine coordinates in Mach 3, the bearings could spill out of the ball nut.  Obviously, I’ll need to have a limit switch…but still, shouldn’t there be some other insurance?

While poring about last night, I came across a posting from a fellow with a capital idea.  Drill and tap the end of the ball screw and put a washer on.  Brilliant!  Now…take a moment to imagine someone with a hand drill trying to make a straight hole down the exact center of a $60 screw.  Not so likely.  Fortunately for me, I’ve got a small lathe and a new set of center drills!  The only hiccup was that my lathe is only 10” long, and I needed more room to get everything lined up. 

Fortunately I had this conversation some months ago with the same friend who bought me the Grabits.  The key is to balance the screw in the lathe chuck, and leave the back half of it hanging out the other side of the head.  In the following pictures you may notice that I did not use any aluminum or brass around the screw to protect it.  Instead, I banked on the likelihood that the screw was quite hard and would not be damaged.  That did turn out to be the case, but if you try the same thing….please consider using some other material to cushion your screw.

This photo shows the ball screw chucked into my lathe.  The screw is probably about 10 or 11 inches long, so some of it is hanging out the back of the headstock.  This actually worked out really well, because the end of the screw was nearly centered and did not require additional support.  If you look closely at the photo, you’ll notice that the center drill is stubby.  Bear in mind that a drill cannot remove chips if you plunge it deeper than the flutes on the bit.  Once I buried the flutes (and figured out why there weren’t any more chips…), I started tapping the hole.

In the event that you have not tapped a hole, it is an irksome affair.  It is very difficult to keep the tap oriented properly to the hole whilst trying to carefully thread it in and out.  Rather than try to center the whole affair by hand, I left the screw chucked into the lathe and put an M5 tap into the stationary drill chuck in the place of the center drill. 

Take Note: I did not, nor would I advise, “power tapping” in this, or a similar situation.  In fact, I put the lathe in neutral and turned it off.  Placing one hand on the three jaw chuck and the other hand on the drill chuck feed wheel, I very carefully worked the tap in and out of the hole.  Due to the shallow depth of the hole, I did not try to tap it very aggressively.  That would make a great mess like the one yesterday, I’m quite certain.  The threads are complete to a depth of about 1/4” though, which should be plenty of thread to keep the table from travelling too far. 

While not terribly glamorous, I’m going to call today a win anyway!