Re: [CAD_CAM_EDM_DRO] Bridgeport SeriesII air assisted knee

Hi Sean

From the maintenance manual for my BP

7.5 AIR ASSIST PEDESTAL

7.5.1 Removal

NOTE: Due to the requirement for the cylinder to be air tight, the cylinder
sleeve is considered to be an integral part of the pedestal assembly and is
removed as a unit.

1. Raise the knee to a sufficient height (not the total travel) to allow
access to the pedestal and elevating nut. Lock the knee in that position and
in addition support the knee with a rope sling.

CAUTION: The assembled knee weighs 875Kg (1930lb). Use appropriate care to
prevent equipment damage and personal injury.

2. Discharge the air from the cylinder and disconnect the air hose and
lubrication line from the top of the pedestal.

3. Remove the screws securing the leadscrew nut mount from the pedistal.

4. Hoist the knee to full travel height, pulling the leadscrew out of the
pedestal along with the packing cup, packing retainer, leadscrew bumper,
thrust bearing and bearing retainer.

5. Remove the two pedestal mounting screws and remove the pedestal from the
base.

7.5.2 Cylinder Gaskit Removal

1. <Same as above section 1. with the same caution regarding knee weight>

2. Remove the pedestal mounting screws and handwind the elevating screw to
withdraw the pedestal from the base to gain access to the bottom fixing
screws.

3. Remove the screws securing the cylinder bottom cover and replace the cover
gasket.

4. To assemble reverse the disassembly procedure.

7.5.3 Packing Cup Replacement

1. Remove the pedestal as described in Section 7.5.1

2. Remove the screws securing the packing retainer, remove the retainer and
packing.

3. Replace with Bridgeport supplied packing (BM part number 2152121). It is
important that this packing has been soaked in a mineral based lubricant
(Mobil DTE 24 or equivalent) for at least 12 hours prior to assembly. Care
must be taken to ensure that the coil spring is in position during assembly.


On the following page is a cross sectional drawing showing the cylinder
assembly - It appears to be a closed cylinder containing a piston and is
sealed by a plate at the bottom.
It looks to be a fairly simple operation to overhaul the cylinder, but due to
the weight of the knee assembly, I would caution you to take EXTREME care.

The part number and weights quoted above my not apply to your particular
mill. Bridgeport apparently badged a number of different machines with the
"Series II" label.

Regards, Paul.

On Saturday 20 October 2001 11:02 pm, sean patterson wrote:
> I have a Bridgeport Series II milling machine with an air assisted knee.
> When air pressure is applied to the base of the knee it leaks very
> rapidly. My question is what is in the base casting and how does the air
> assist system work? I am currently using the mill without it as it hasn't
> worked since I purchased it. Will feed rates be higher with the air?
> Thanks
> Sean