 
Gy-Roll
twin spindle and multi-spindle heads are specially designed for
use with small self-feed drilling units. These self-feed drills
are primarily intended for the drilling and tapping of small holes.
As it is more often necessary to drill a group of small holes
instead of a single hole and since such groups are often on close
centres, it is important that a head specially designed for these
units be capable of drilling on the closest possible centres.
The minimum centre distance for Gy-Roll heads is approximately
twice the maximum drill diameter.
Since
the heads may be run at high speeds, particular care has been
given to the design of the bearings for the internal gearing and
spindles. All journal bearings are precision ground and needle
bearings have caged rollers so that friction and subsequent wear
is kept to a minimum. Axial spindle load is taken by a roller
thrust bearing with a rating at least three times greater than
a ball thrust bearing of an equivalent outside diameter.
Standard
drilling adaptors and reversing tapping adaptors are supplied
to suit most self-feed drilling units and air motors. Special
adaptors for other units can be quoted for. The heads can be supplied
for general workshop use with a taper shank for fitting directly
into a drilling machine spindle or with standard flange or spigot
locations for adapting to a drilling machine quill.
The
screw back type of collet used in Gy-Roll heads provides the maximum
drilling capacity in relation to the spindle diameter. The type
950 and 1250 heads can be supplied with either the screw back
type of collet or with spindles to suit automotive drill adaptors.
The
lubrication system in all Gy-Roll heads is designed in such a
way that oil is released by capillary action from reservoirs as
and when it is needed. The oil reservoirs provide oil to the spindles
with the head in any position from vertical to horizontal. The
oil is of a standard motor grade which is easily obtainable.
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