Gib tightening.. was Asian Import mills,

Thanks for your reply and nice ASCII art!

I am not sure I know what you are saying, yet. I printed this out and
will study your response. If I have any questions I will ask.

CADMAN

--- In CAD_CAM_EDM_DRO@y..., ballendo@y... wrote:
> Cadman,
>
> This is a tapered Gib. As the single screw moves it in and out it
> DOES tighten and release the clearance on the axis. The sherline
uses
> a similar technique.
>
> There are a couple of gotchas however:
>
> 1) The taper of the gib needs to match the machined taper of the
> saddle for the gib to have equal pressure/adjustment along its'
> full length.
>
> 2) The slot FOR the adjusting screw head is wider than the head of
> the adjusting screw. This allows the gib to move when the axis
> changes direction, which means it is either too tight or too loose
> (depends how you look at it <g>) during one direction of travel.
>
> For 1) You can lap the gib and axes to a better fit than the
factory
> provides. Be sure to use non-embedding lapping compound. It is
> available at Mcmaster-Carr. It is also worthwhile, IMO, to dis-
> assemble the xy table and do some de-burring of ALL these parts!
>
> If you lap, keep in mind that you DON'T want a completely shiny flat
> surface on the ways! This will make them stick, and is the reason
> there is a pattern of "scratches" to let air/oil into the space
> between and prevent this sticking on the machine as delivered.
>
> For 2) Fit a shim in the slot or make a new adjusting screw to
> eliminate the sloppy adjustment of the gib. This is probably the
> single most important mod to do to a mill/drill. If you have a
lathe,
> you can turn a "step" in the outer part of the top of the adjusting
> screw. Then turn a ring (same diameter as the screw head) to fit
> tightly and glue/braze in place. This "extends" the screw head,
while
> still allowing the slot in the screw head to be used for adjustment.
> Now face the added ring to the EXACT thickness of the slot in the
> gib. a file or emery paper can be used for final fitting.
>
> ___ ___
> | |_| |
> |___ ___|
> < >
> < > orig. screw
> < >
> _ _
> | | | | -- ring to extend head thickness
> |_| |_|
>
> _ _
> _| |_| |_----- Turned recess in head fits ring above
> |___ ___|
> < >
> < > modified screw
> < >
>
> Hope this helps.
>
> Ballendo
>
> P.S. I've always thought a Jib was a foresail on a boat :-)
>
>
>
> <snip>What bothers me is the "Jib
> >adjustment" They only give one screw to tighten the ways. It is
> >located at the end of the jib (If you can believe that). I am not
> >sure if it does anything at all. The only real jib tightning is
> >done by the way clamps. You know the ones that you tighten to lock
> >the way from moving.
> >
> > CADMAN