Ignoramus9618 wrote:

On 2010-08-11, Ignoramus9618 wrote:
The way my mill is set up, is that the spindle is hollow on top (it is
hollow all the way). Top of the spindle is accessible from top of the
head. It is covered by a steel plate with a hole opening.

1. It is not clear if the ID of the spindle top is greater or less or
the same, compared the ID of the hole in plate, which is 26mm.

The top plate, according to some reports, holds a bearing inside and
is not easily removable.

Do I have any practical alternatives to buying a bore gauge, to
measure spindle ID?

2.

Oops

2. I would need to somehow mount a shaft to protrude upwards, from the
spindle, and to "fix it" inside the spindle. What is the best, proper,
etc way of doing so.

thanks

1. Stick a 1" (25.4mm) end mill / drill / rod through the top hole and
see how it compares to the spindle hole? Poke around with different size
end mills / drills / rods until you find one that is a close fit to the
spindle hole?

2. Turn a shaft with a close fitting insert section and Locktite it into
the spindle bore? Ensuring you keep the extension shaft aligned will be
the trick. I'd suggest making the encoder plate that mounts on top of
the mill with a bearing in it to keep things centered and not allow side
movement of the shaft in the encoder.

Also, before you get too far into this, double check that the spindle
portion you are looking at doesn't move with your Z axis. If you Z is on
the spindle ram, I'd think that the top of the spindle moves down with
the Z. It certainly does on the series 1 mills with a drwabar.