Re: [CAD_CAM_EDM_DRO] Mounting Limit switches to a BP clone (knee mill)

Peter R wrote:

>Hi gang,
>
>Has anyone drilled and tapped a hole into the table of a knee mill? I'm
>not sure if just the sliding surfaces are hardened or all over? By
>delicate scratching, it doesn't appear to be hardened.
>
>I've previously used unsealed microswitches (mounted to the cast iron)
>for my limit switches and while they have lasted well in most locations,
>one of the switch positions always catches drips of way oil and over
>time seems to go intermittant in its closure point - causing problems
>with zeroing the X axis. I've just ordered some sealed limit switches
>from Digikey but they are smaller and have a roller rather than the long
>lever of my existing switches. The best and cleanest mounting location
>will require me to drill a small hole in the side of the table just
>obove the sliding surface to mount an actuator arm. This new location
>will also give me an additional 3" of table travel in the X direction -
>which never goes astray! Has anyone drilled into the table? Having
>just broken a tap in stainless steel - I will figure another way if all
>the surfaces are hardened.
>
>

I think you will find the material can be easily drilled and tapped. It may
be a little harder than the white cast iron of the original Bridgeports, but
still quite workable. Bridgeports are not "hardened" as far as I know, they
had an optional "hard chrome" plating on the way surfaces.

Clones may have flame-sprayed hardfacing applied in the same places,
again on a relatively mild casting.

Jon