Re: [CAD_CAM_EDM_DRO] Re: Bridgeport 2J-2 Head Noise

vavaroutsos wrote:

>Jon, I called it a resonance because the sound doesn't exist at low
>speeds and seems to build up as the speed is increased and then
>decreases slightly at very high speeds. It is a clanking sound. The
>back gear seems to be tight with no play and I don't hear any noise
>when turning the motor pulley manually. I do recall hearing the noise
>as the motor slows down, so this seems indicative of the variable
>speed mechanism. I'll have to check this again.
>
>When I changed the three upper head bearings, after getting the
>machine, I inspected the plastic bushings you speak of. They were
>rather thin, but seemed to be fairly snug to the shafts. I figured
>they were thin to begin with. Is this not the case?
>
>

I don't have a vari-speed, and because I need a VFD to make 3-phase
power anyway, I
really don't want one. I only know a little about them from work and
the news group.
I think as long as the bushings are complete and the pulley sheaves
don't wobble
eccessively, you don't have a problem. I think it is when the bushings
crack and a section
breaks off that it allows the sheave to gouge up the shaft.

>The upper housing on the CNC mills seems a little harder to remove
>than you describe. I don't see any way to pull the whole thing off.
>It looks like it has to be disassembled a layer at a time. I already
>had it torn down to the top of the gear box to replace the three
>upper head bearings and it wasn't fun.
>
>

Well, again, I don't have one, but there is only one section that is
different between the
1J and 2J heads. There are 3 nuts at the top of the main housing that
hold vertical t-bolts
on the 1J, allowing the belt housing and motor to swivel. Due to the
linkages between
the high-low shifter handles, the 2J belt hosuing does not swivel, and
studs go into
fixed spots of the belt housing, instead of t-bolts in a round track.
But, those 3 nuts
still hold the belt housing down onto the top of the main housing. I'm
pretty sure
the housing can be lifted off after removing those nuts and the shifter
linkage.
There may be other ways to take it apart to get to the 2J back gear, though,
which you can't do on the 1J.

I'm sure the 2J is more involved than the 1J. I can pull the motor and
belt housing
in about 5 minutes on the 1J.

Jon