Drill guide and support therefor

An optical drill guide and a drill guide support for electric hand drills. The drill guide consists of a front sight aperture framed with a light color and a rear sight aperture formed by a translucent ring. The line of sight through the guide is arranged to be aligned with the longitudinal axis of the drill. The drill guide is used in conjunction with a mirror placed on the work surface so that when the guide is aligned a reflected image of the front sight surrounds the translucent ring. The guide is adapted to be integral with or detachable from the electric hand drill. When detachable, a drill guide support is provided which includes mounting means the ends of which are resiliently biased towards each other and adapted to be received in the housing of the drill to align the guide with the axis of the drill.

FIELD OF THE INVENTION 
A guide for the portable electric drill assists the operator in guiding the 
bit along the desired axis when drilling. Some guides will also assist in 
starting the hole, in limiting its depth, or in drilling into special 
shapes. The disadvantages of all known guides have greatly restricted 
their use and it is significant that none have been recommended for such 
routine uses as preventing the flexing and consequent breaking of small 
bits. The purpose of this invention is to provide a guide for the portable 
electric drill which may be either built into the drill housing or be 
detachable on it, and is sufficiently convenient and versatile to 
encourage habitual use. 
DESCRIPTION OF RELATED ART 
U.S. Pat. No. 3,906,640 (Sosa, 1975) teaches a pair of spaced sight 
openings on the drill housing (the rear one narrower) with their line of 
sight parallel to the axis of the spindle, and a mirror laid on or 
parallel to a flat work surface. When the images of the sights in the 
mirror are concentric the axis is normal to that surface. 
The disadvantages of Sosa's guide are discussed below but it does have 
advantages which, as a group, distinguish it from all other drill guides. 
It can be used with any bit and without reducing the effective length (cf. 
Stanley Drill Guide, Black & Decker Drill guide). It is small and light 
enough to be built into the drill housing (cf. Black & Decker 
"Guidemate"). Sosa's detachable version need not be firmly attached to the 
housing (although his is) because it is not stressed in use. Further, its 
alignment is easily checked by using a "mirror and post" (cf. Sosa's 
"auxiliary reflector device"): a mirror laid on any flat surface from 
which a short rod projects at 90.degree.. The use of the guide is not 
absolutely limited to drilling normal to a flat surface as implied by 
Sosa; for example, small workpieces may be held in a vise on the jaws of 
which the mirror is laid. 
To supplement Sosa's plain mirror, the present invention provides a mirror 
fitted with a protractor capable of supporting it at any angle between 
0.degree. and .gtoreq.45.degree. to a flat work surface. To drill at an 
angle .alpha..degree..+-..ltoreq.1.degree. to such a surface, the mirror 
is set at (90-.alpha.).degree. to it. To position the mirror when the work 
surface is not flat, the drill may be held at the required angle with the 
bit at the point of entry while a plain mirror is attached to the work 
(e.g. with plasticine) so that the images of the sights are concentric. 
Alternatively, a "mirror and post" (with a longer and lighter post) is 
similarly attached (but without reference to the drill) with the post at 
the desired angle. 
When built-in, Sosa's rear sight is necessarily obtrusive (and thus 
vulnerable) because it requires light from the front to make its image 
visible in the mirror. The present invention provides a rear sight-hole 
which is defined by a ring of translucent or transparent material and 
light from the side or rear then makes the image of the ring visible in 
the mirror. When the sights are built-in, the rear sight may then be 
buried in the housing like the front. Further, built-in or not, the sight 
holes may be the ends of a tube. 
Sosa's detachable guide (like the Black & Decker "Guidemate") is mounted on 
an adjustable shoe which is held by a strap around the belly of the drill 
housing. Attaching and aligning are then awkward, more so because 
simultaneous, and the seating is unstable on some housings. "Portalign" 
and the Black & Decker Drill Guide are attached to the spindle of the 
drill, a feature common to all drills, which ensures that these guides can 
be attached to any drill and are self-aligning. However they too are 
awkward because the chuck must be replaced on the spindle by the guide, to 
which the chuck is then re-attached. They may also spin off if the drill 
is reversed. 
SUMMARY OF THE INVENTION 
In addition to the drill guide, the present invention provides a support 
which renders it instantly attachable/detachable and, self-aligning on any 
drill housing which either has vent slots beside the fan or has been 
adapted to the support. It is equally suitable for mounting tubular 
sights, Sosa's sights, or other unstressed guides like spirit levels. Here 
the tube whose ends represent the sights is adjustably mounted on a base 
which is fixed to the apex of a "bicycle pant" clip so the axis of the 
tube is normal to the general plane of the clip and may be adjusted about 
1.degree. in any direction. The clip sits over the housing with its ends 
modified to seat in the vent slots (if any) beside the fan, and is 
maintained in the plane of the slots by two legs which adjust to the width 
of the housing and seat in them. These legs are bolts which penetrate the 
clip about 11/4" from its ends and lie in its plane. 
The axis of the spindle is substantially normal to the planes of the gears, 
of the fan, and of the vent slots beside it. It is thus substantially 
normal to the plane of the clip thus installed, and parallel to the axis 
of the sight tube. Consequently the guide is substantially aligned. 
Should there be no vent slots beside the fan, the ends and legs of the clip 
seat in holes in two plastic pads (ca. 
13/4.times.3/4.times.7/16.times.1/16") which are glued to the housing. 
These pads are initially located for gluing by setting up the drill with 
the guide and its support on a "mirror and post" (as for checking the 
alignment), with each unglued pad under an end and a foot. The pads etc. 
are moved as a unit on the housing until the concentric images of the 
sights show that the pads are in a correct position for gluing. 
Attaching and detaching the detachable guide will not alter its alignment 
but the latter should be checked and corrected, by using the "mirror and 
post" to adjust the sight tube on its base, whenever a guide is installed 
on a drill for the first time, when it is transferred to another drill, 
and when maximum accuracy is required. 
Thus in one aspect, the invention is a drill guide for use with a portable 
electric hand drill comprising a pair of apertured sights, the front sight 
having a light coloured face surrounding the aperture, the smaller rear 
sight aperture being framed by a translucent ring such that when in use a 
reflected image of the front sight and the translucent ring may be seen 
and aligned without the rear sight being open to forward illumination, 
both sights being adapted to be received on an electric drill such that 
the line-of-sight through said drill guide is substantially parallel with 
the longitudinal axis of a drill bit held in the drill. 
In another aspect, the invention is a drill guide support comprising 
mounting means adapted to surround the top and both sides of a portable 
electric hand drill, each end of the mounting means being biased towards 
the other and including a foot and an arm, each of which is adapted to be 
releasably received as a close fit in an air vent in the plane of the fan 
of an electric hand drill, the mounting means being adapted to support a 
drill guide thereon in alignment with the axis of the spindle of the drill 
when the drill guide support is mounted on the hand drill. 
In a further aspect, the invention is a drill guide support comprising 
mounting means adapted to surround the top and both sides of a portable 
electric hand drill, the housing having an unapertured surface, each end 
of the mounting means being biased towards the other and including a foot 
and an arm, each of which is adapted to be releasably received as a close 
fit in recesses formed in a pair of seating pads affixed to each side of 
the housing, the mounting means being adapted to support a drill guide 
thereon in alignment with the axis of the spindle of the drill when the 
drill guide support is mounted on the hand drill.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows one form of the drill guide in longitudinal cross-section. The 
guide consists of a tubular member 10 having a front sight 11 and a rear 
sight 12 which are coaxial. The inside wall 13 is preferably a dull black 
colour. The end 11a of the front sight 11 surrounding the circular opening 
14 is a light colour preferably white. The rear sight aperture 15 is 
framed by short hollow cylinder or annulus 16 of clear or translucent 
material. The annulus may be located behind or within the rear sight 12. 
The openings may be of any convenient shape and need not be circular, but 
circular is preferred to permit easy alignment of two circles so as to be 
concentric, as will be later described. 
Preferably, the tubular member 10 is formed of metal or rigid plastic and 
has a length of approximately four inches. A preferred inside diameter is 
approximately 1/4 inch. The translucent annulus 16 may have an inner 
diameter of approximately 3/32 inch and an outer diameter of approximately 
1/4 inch. It may be formed of clear or translucent plastic tubing or the 
like. 
When a user looks into the rear sight into a mirror surface resting on a 
plane to which the axis of the guide is normal, the user sees a pair of 
concentric light coloured rings as seen in FIG. 2. Ring 18 is the image of 
portion 11a of the front sight and ring 19 is the image of the annulus 16. 
Thus, the use of translucent material provides an image without requiring 
any frontal illumination of the drill guide. Frontal illumination would 
require the rear sight to be in an exposed and, hence, vulnerable 
position. 
The drill guide of this design may be constructed integrally within the 
housing of an electric hand drill, as indicated diagrammatically in FIG. 
3. In this case a free line of sight extends from the front sight 11 to 
the aligned rear sight 12 and there is no need for tubular member 10 
(although one could be used) since the sights are supported by the drill 
housing. That is, the front sight 11 is formed in the housing and an 
unobstructed passageway extends to the rear sight 12, which supports an 
annulus 16 as described above. 
The drill guide of the present invention may also be mounted to the surface 
of the drill housing with appropriate supporting and adhesive materials 
which may harden and hold the guide permanently in place. In such an 
arrangement the guide should be flat against the housing to minimize bulk. 
With this arrangement it is necessary to align the guide so as to ensure 
that the axis of the drill guide is parallel with the axis of a bit 
installed in the drill. One method of achieving this is to use a mirrored 
surface of suitable size with a post mounted at right angles. The post may 
be installed in the chuck of the drill and then the drill guide is 
installed to its final position when the images of the sights are 
concentric as shown in FIG. 2. Such a post with mirror is taught for 
example in U.S. Pat. No. 3,906,640 (Sosa). 
When the drill guide is to be used to drill holes normal to a flat 
workpiece a plane mirror is employed with the guide. As may be seen in 
FIG. 4, mirror 20 is positioned flat on the workpiece adjacent the hole to 
be drilled. The drill bit is set a the correct location (or in a hole if 
necessary) and the user aligns the sights as described above. The user 
guides the drill while the hole is being drilled by holding the drill such 
that the circles in the reflected image, remain concentric. 
When the user wishes to drill a hole at an angle less than 90.degree. to a 
flat workpiece a mirror mounted on a protractor may be used as shown 
generally at FIG. 5. As shown, the drill bit 21 is intended to enter the 
workpiece 22 at an angle 23, which is the same as angle 24 seen in FIGS. 5 
and 6. 
The protractor is shown in FIG. 6 and comprises a plate 25 and a post 26 
which is received in the plate 25 in slidable manner at right angles. The 
plate supports the mirrored surface 20. The post may be held in place by 
any means such as a set screw 27 and angle 24 varies according to the 
amount to which the post 26 penetrates the plate 25. When the post does 
not project through the plate, the angle 24 is 90.degree. and angle 24 
decreases as the post 26 projects further below the plate 25. It is 
desirable that the post include a scale 28 along its surface to give a 
direct reading of angle 24. 
When the user wishes to drill a hole at an angle of less than 90.degree. 
onto a flat workpiece the post 26 in the protractor is adjusted to the 
desired angle using the scale 28. The user then drills a shallow pilot 
hole at the desired location. This fixes the position of the hole. The 
user then sets the protractor as shown in FIG. 5 adjacent to the hole to 
be drilled so the plate meets the workpiece along a horizontal line to 
which the horizontal component of the axis of the hole is normal, and the 
images of the sights can be seen in the mirror when the bit is at roughly 
the desired angle. The user then uses the guide to align the drill until 
the circles of the sights appear concentric in the image reflected from 
the mirror, as discussed above. The user maintains the angle by using the 
guide as described until the hole has been drilled. 
When the surface is not flat, the user makes the starting hole, holds the 
bit in it at the required angle, and supports the mirror with plasticine 
so the images of the sights are concentric, then drills the hole as 
previously described. Thus, the user may drill the desired hole in a 
controlled fashion. 
FIGS. 7 and 8 show a drill 31 with drill guide support installed thereon. 
The drill guide support comprises a mounting means or clip 32 the ends 32a 
and 32b of which are resiliently biased towards each other and thus 
towards the sides of the drill housing. The mounting means 32 may comprise 
a band of spring metal or other resilient material similar to a bicycle 
clip capable of providing sufficient force to bias the ends 32a and 32b 
towards each other and hold the drill guide and support in place during 
use and yet to allow easy removal by hand. The cross-section of the 
mounting means may be concave to resist out-of-plane deformation and 
assist in maintaining it engaged with the sides of the drill housing. The 
ends of the mounting means 32 may be received within appropriately 
positioned air vent slots if provided in the housing of particular 
electric hand drills. Support arms 44 and 44' aid in providing stability 
in the mounted position. 
If appropriate air vent slots are not available then special pads 41 may be 
attached to the drill housing to receive the ends of the mounting means, 
as described below, FIG. 8 is a composite to show the two modes of 
attachment, end 32a is shown engaging an air vent slot and end 32b engages 
a pad 41. Dealing first with end 32a engaging an air vent slot, it will be 
appreciated that the spindle of the drill will be found to be parallel to 
the axis of the fan and normal to the plane of the fan and the air vent 
slots. A distancing adjustment screw 45 is provided to be adjusted so that 
the end 42 and chisel shaped member 44 snugly contact the air slot in the 
drill housing, providing sturdy support. A locking nut or wing nut 46 
maintains the distance of the arm from the mounting means once it has been 
set for the particular drill housing for which the support is adapted. 
In the absence of such slots, seating pads 41 may be applied to each side 
of the drill housing. As seen in FIG. 9, each seating pad includes a first 
recess 41a and a second recess 41b. First recess 41a is of a shape adapted 
to snugly receive a complementary shaped foot 42, identical to that used 
with the air vent, at the end 32b of the mounting means 32. The shape of 
the end of the foot 42 matches that of the recess 41a to provide snug 
engagement. In this case arm 44 consists only of the machine screw 44' 
received in recess 41b. To aid in adjustment of screw member 44' a knob 
45' is attached to its outer end for manual rotation. 
The drill guide 33 is held in a support 34 affixed preferably at the apex 
of the mounting means 32, as shown in FIG. 8. The support 34 is a frame to 
support the drill guide 33 which may comprise a tube, as shown. The drill 
guide may be held reasonably rigidly at the front end 33a. The rear end 
33b may be held in the support by elastic bands or a resilient spring so 
as to allow slight movement within the support 34. This is because slight 
adjustments of the order of 1.degree. or less may be necessary when using 
different drills. The alignment of the sight may be adjusted within the 
sight support by means of a horizontal adjustment screw 35 and vertical 
adjustment screw 36 which are adapted to cause the rear end 33b of the 
drill guide to pivot laterally and vertically, respectively, about the 
front end 33a. The exterior portions of the tube which abut adjustment 
screws 35 and 36 are flattened so that the tube is stable when adjusted to 
any position. 
The spring characteristic of the mounting means 32 provides sufficient 
pressure on the end portions 32a and 32b and arms in the recesses of the 
pads 41 against the side of the drill to hold the drill guide support in 
place. The four points of contact (namely, both pairs of feet and arms) 
ensure that the mounting means 32 is reproducibly aligned immediately upon 
installation. 
When seating pads 41 are used, at the time of installation glue is applied 
and the seating pads 41 positioned in place on the housing of the drill. A 
mirror mounted on a surface with a post normal to the surface is installed 
in the drill, as taught by Sosa in U.S. Pat. No. 3,906,640. Alternatively 
the mirror and protractor device earlier described may be used. The 
mounting means are then installed over the drill by spreading apart the 
ends 32a and 32b and aligning the feet 42 with each recess 41a in the 
seating pads 41. The distancing adjustment screws 45 are adjusted so as to 
allow the machine screws 44' to sit within recesses 41b and the locking 
nuts 46 are tightened so as to fix the position of the arms. Before the 
adhesive on the seating pads 41 is finally set, the final position of the 
seating pads is checked by ensuring that the drill guide 33 is parallel 
with the axis of the drill spindle (concentric arrangement of rings 18 and 
19). This allows for final adjustments of the exact position of the 
seating pads 41 before the adhesive hardens. After the adhesive has set 
affixing the seating pads 41 in place, the mounting means 32 may be easily 
mounted and demounted from the seating pads. As can be seen in FIG. 8, 
pads 41 conform closely to the surface of the drill housing without 
projecting significantly and are not vulnerable to being displaced. 
After the glue has hardened, any adjustment of the drill guide 33 within 
the support 34 may be accomplished by adjusting the horizontal adjustment 
screw 35 and the vertical adjustment screw 36 using a post and mirror as 
described above. This allows the accurate alignment of the sights to 
ensure that axis is parallel with the spindle of the drill, and is 
generally necessary when the guide is transferred from another drill which 
is a different model. Once this adjustment has been made, the drill guide 
and support may be attached and detached as the user requires and further 
adjustment is not normally necessary. 
Although specific examples of using existing features of drills, such as 
the apertured housing of FIG. 3, the apertures being provided by the air 
vents, to support the drill guide have been give, these examples are not 
exhaustive. Any surface feature which provides a stable, reproducible 
position can be used. For example, a sharply defined recess on the top 
surface of the drill housing can engage a corresponding projection on a 
moulded shoe; the shoe being held to the housing by spring biased arms 
similar to arms 32 but without any locating features. The bolt hole 
adapted to receive an auxiliary handle can be used for positioning such a 
show. Any such attachment is, of course, specific to a single drill model. 
As a different example of such a structure, FIG. 10 shows a shoe 50 
contoured to fit the top surface 51 of a drill housing 52. The shoe is 
provided with pins on its under surface (not shown) which engage with bolt 
receiving recesses 53. The shoe has an open channel at one side forming a 
drill guide having forward and rearward sights 56 and 57. 
It has been found in practice that the resiliency of the mounting means 32 
is sufficient to hold the support in position so as to maintain the 
alignment of the guide to allow accurate drilling particularly where the 
cross-sectional shape of the support is concave or ribbed rather than 
rectangular. At the same time, because the drill guide support is held in 
place only by the biasing forces and not through any more permanent 
affixing means, the guide is easily and quickly attachable and detachable. 
While only certain embodiments of the design have been illustrated and 
described, it is understood that these are presented by way of example 
only and variations will be clear to those skilled in the art. For 
example, the transparent annulus 16, could be formed by dipping the end of 
the tube into a liquid plastic and allowing it to harden. The disclosed 
drill guide support is capable of holding various kinds of unstressed 
sights. Not only could the sight previously described be used but the 
detachable sight taught in U.S. Pat. No. 3,906,640 (Sosa) could also be 
used with the detachable drill guide support.