The Mill is damn near done! Or is that "done for"...?
by Doc Nickel
As I posted about a week ago, I've been puttering with the new-to-me Exacto mill again lately, in part because I want to get the damn thing done and be able to use it, but mainly because I need to get all the loose head parts off my bloody welding table so I can actually do some work on it!
In that last post, I figured the head was about 70% done, and in this intervening week, I was able to complete the last 30%. And today I was able to temporarily wire it up to a VFD, and put power to it!
And it works!
... Except we now have a brand-new problem. A Houston-we-have-a-problem, problem.
The spindle, as it turns out, is bent, and badly. There's a full 15 thou of wobble on the OD of the spindle nose.
Doesn't sound like much, to you non-machinists? If you'll recall that issue I was having with the Jet mill-drill last year, that surface finish issue was likely caused by less than one thou of movement. 15 thou of spindle wobble on a machine tool is like using a dull axe to trim your toenails.
It is, however, probably not fatal. I'll have to yank the quill and pull the spindle, and using a surface plate, find out how and where it's bent. Then, hopefully, with some care and a gnarly hydraulic press, gently straighten it out.
Once it's reasonably straight- or straighter- I'll pick up some fresh bearings (any crash bad enough to bend the spindle almost certainly killed the bearings) and then once it's reassembled, regrind the spindle collet taper just like I did on the Jet spindle.
Wish me luck. If the spindle or quill winds up bad or unusable on this machine, that basically junks the whole thing, unless I'd be willing to spend between $1K and $2k on a used Bridgeport or other mill head, and figure out a way to adapt it.