Ball Screws for my Mill ?

CNCers:

If you remember, I'm trying to retrofit my Supermax knee mill for
CNC.
I'm currently (still) trying to verify that a Bridgeport ball screw
kit will work on my mill. From what I've found and measured it will
be far easier to start with a kit than with bare ball screws and nuts.

I've found kits manufactured by Nook (PowerTrac), Thomson Saginaw and
Hiwin. I've also found kits supplied through McMaster Carr,
Microkinetics and a mid west group GL Centroid. However, I don't
know
what manufacturer supplies these last three. The prices are all over
the map:

Nook +/- .001 "/ft $1665
Thomson Saginaw +/- .0005 "/ft $3821
Hiwin +/- .0005 "/ft $ 950
+/- .002 "/ft $ 600

McMaster Carr +/- .003 "/ft $ 742
Microkinetics +/- .003 "/ft $ 975
GL Centroid +/- ? $ 900

I thought the Thomson Saginaw were rolled threads but by the
tolerance
and cost they must be ground. I figure I must be getting a mix of
wholesale and retail prices??

But now for my question. My mill has a 9x42 table and I've pulled
the
lead screws and measured them. They are very close to the drawings
for these Bridgeport kits but for one dimension. The Y lead is
longer
than indicated for a 9" table. In fact, it matches the dimensions
for
the 12" Bridgeport table. The Y travel on my SuperMax is specified
at
12". Does anyone know the Y travels for Bridgeports with 9" and 12"
tables? Is anyone familiar with these Taiwan 9x42 mills having
longer
than normal Y travel? I suppose it could be a weird duck.

But for the above dilema I'm sure I will, at most, need to re-build
the bearing mounts on the ends of the tables and on the front. I
already plan to rebuild two of these to incorporate motor mounts so
this wouldn't be a big deal. I plan to order a Hiwin ball screw set
as soon as I convince myself exactly which lengths to get. There is
an 8-10 week lead for these directly from Hiwin, but for $150 to $300
savings......

As an update on my project, I have a computer up and running Red Hat
linux with the real time extension and EMC installed. It'll dual
boot
linux or MS-DOS so I can use other dos based CNC software if needed.
I plan to stay with EMC though unless I run into problems.

I've ordered Camtronics 3 axis 5A stepper driver boards and two size
34 stepper motors at 785 oz-in for the X/Y axes. I plan to get these
going and then design/build a spindle drive for the Z. I've received
a partial order with the rest to follow within the week. Haven't
started to build the drivers yet but so far the service from Dan
Mauch
at Camtronics is excellent.

I narrowed it down to Camtronics or Gecko stepper drives from
following the list and reading archived posts. The Camtronics route
(kit) was somewhat less expensive and I was a little worried about
the
microstepping of the Gecko drives. As I understand this, the
computer
needs to put out 10x the pulses for the equivalent motion of a full
step drive. I was a little worried about the speed but I may be
mistaken here. The Camtronics running half step should work well.

I plan to run X/Y via a 2:1 timing belt reduction but haven't sized
any of this yet. Will be in touch with progress and/or questions.

I do want to thank those on the list for the support. I don't think
I'd have had the confidence to undertake this without your support.
Thanks.

Hugh