Re: newbie needs advice

John,

FWIW, most of the factory made Bridgeport sized mills use either 29
lb-in or 40 lb-in servo motors. For whatever reason those seem to be
the standard motors used in these mills. My biggest mill is slightly
larger than a regular B-port and uses the 40# motors belted 1:1 to
the screws (not sure of the screw pitchs, 4 or 5tpi?).

With the 40# motor about the max speed it'll do is 300 ipm rapids
which is acceptable for a mill of this size doing low production
work. The X&Y axes have adequate force, the Z is a little weak for
heavy drilling.

My advice is don't undersize your motors. I've seen a few
conversions with too small motors and rapids in the 50 ipm range.
IMO, those mills are practically worthless for any money making work
or re-sale. Using one would be like watching trees grow, very
frustrating.

Incidently, the Baldor 40# motors for my mill cost about $875 each,
that's with connector, ready to bolt in. The manufacturer now offers
an SEM brand motor, same specs, ready to bolt in for around $750.
Last time I needed a motor, after a lot of scrounging, I concluded
the factory prices were as good as any I could find since those
motors would get me back up and running in a few hours.

Doug

--- In CAD_CAM_EDM_DRO@egroups.com, "John Hudak" <jh1221@a...> wrote:
> Hello, I am in the process of converting my bridgeport mill to cnc
> control, and have already purchased the ballscrews, and the drivers
> (gecko) at this point I am looking at the motors, and am a little
> confused about the sizes that might be needed, I have seen some
> conversion kits with 1200 oz motors that are reduced 2 times. Does
> this give 2400ozs of force??? what is the minimum size motor that I
> should use? I plan on using this mill for hobby work with a small
> cash job thrown in here and there. Thanks; John