Civil Engineering Reference
In-Depth Information
Fig. 12.8. A set of telescopic gauges suitable for checking bored holes.
If we cannot use the component or a gauge, a good alternative is a tele-
scopic gauge. These are simple to use and very accurate. You put the tele-
scopic gauge into the bore on an angle and lightly nip the locking screw. Then
carefully straighten up the gauge in the hole. The gauge will close down to
the exact diameter of the hole, and you can then tighten it up and measure it
with a micrometer. This will give you an accurate reading of the hole size. It is
advisable to run the boring bar through the hole a couple of times at the same
setting to ensure any deflection is removed.
Boring a seating for a chimney
Cutting a scallop, for instance to shape the bottom of a chimney to fit the boil-
er barrel, is an easy job with a boring head. Set up the chimney horizontally
with the scallop end nearest to the boring bar. Set the boring head centrally to
the centre line of the chimney.
To set the correct radius on the boring bar find the edge of the bar's face.
Move the table away by the 100mm boiler barrel radius so you are exactly
100mm away from the workpiece's face.
Put the boring bar and tool into the machine's spindle and open out the bor-
ing head until the boring tool just touches the bottom face of the chimney. The
boring bar is now set to the exact radius of the boiler barrel, 100mm.
