On Mon, 01 Nov 2010 09:32:40 -0700, Tim Wescott
wrote:
On 11/01/2010 08:31 AM, Wild_Bill wrote:
Tim, if you haven't had the mill head column off of your machine to
improve the metal-metal contact area to the headstock top surface, you
might consider doing this procedure to gain some rigidity when milling.
The one I worked on was a 12x20 made in 1999 maybe.
While you're milling something fairly aggressively, put your left hand
fingertips at the seam of the contact surfaces at te base of the column.
If you feel movement, this procedure may increase milling rigidity
considerably.
The mating surface of the column flange is likely fairly accurately
flat, as it was probably turned (faced) on a lathe.
The top surface of the headstock may be one of those areas where a
factory worker ran a power scraper on it, just to smooth it somewhat,
followed by filling the seam gap with filler putty.
I managed to get the headstock surface flat, by rough filing, and
checking for contact area with plain printer paper laying on the
headstock surface, and rubbing a (machined flat with a large shell mill
on a large machine) flat thick slab of aluminum on the paper to make a
carbon copy (although aluminum oxide) of the contact area.
I put cardboard and shop rags in the opening to catch the filing swarf.
When I started, there was probably only about 15% contact between the
two surfaces.. when I had finally had enough exercise, the contact area
was probably closer to about 75%, and the rigidity of the mill was
increased greatly as a result.
My biggest complaint about rigidity on that thing is the quill, which I
can somewhat deal with by adjusting the quill lock.
My biggest complaint about the use of the thing as a mill at all is that
the quill drive (which is the only adjustment in the z plane) is much
coarser than the x and y feeds and an odd number in both english and
metric, being something like 0.43 inches. To top off the pain, it's got
an itty bitty knob. So even when I've got the rigidity issues dealt
with, it's very difficult to get the height difference between features
accurate.
So even if the thing were made out of tungsten and worked as smooth as
silk, I'd still be wishing for a mill that had a decent vertical feed
mechanism.
Can I interest you in a Gorton MasterMill?
http://picasaweb.google.com/gunnerasch/NewGorton#
Needs a bit of work, but nothing major and would be a fun winter project
for folks
Gunner
"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,