Center scribing kit for use with drilling templates

#The instant invention relates to template guided drilling. More particularly, the invention relates to apparatus adapted for assisting of machinists in utilizing drilling templates.

#Drilling templates are commonly serve dual functions of drill site location and tactile/visual assistance in drill bit selection. Where, for example, a drilling template prescribes a square four inch on center pattern of diagonally paired ⅜″ and ½″ holes, such template will commonly comprise a flat aluminum sheet having holes positioned and sized identically with the holes to be drilled. Such an aluminum sheet template efficiently facilitates tactile/visual selection of the ½″ and a ⅜″ drill bits needed for drilling. In selecting the drill bits, the operator of the template simply slides a candidate drill bit through one of the template holes to assure that the bit is of the proper gauge. If such bit will not slide through the hole in the template, the bit is immediately identified as too large. Conversely, if the candidate bit fails to closely fill the hole in the template, such bit is identified as being too small.

#The exemplary drilling template less efficiently locates the prescribed drilling sites upon the surface to be drilled. Upon placement of such drilling template over such surface, the four drilling sites are known to be at the centers of the four holes of the template. However, the exact locations of the centers are not immediately identified. A skilled machinist may be able to closely approximate the center of each hole utilizing a scratch awl to indent the drilling sites. However, in many applications, the tolerance for inaccuracy in drill site location is beyond the marking capability of a machinist. The instant inventive kit or assemblage assists drilling template operators in performing such drilling site locating function by providing a quill and stylus scribing instrument; the instrument having a plurality of interchangeable scribing point centering guides; such guides matching common gauges of drill bits.

#FIG. 1 is a side view of the quill and stylus assembly of the instant invention, such assembly having an exemplary interchangeably attached stylus end centering guide configured as a second quill.

#FIG. 2 includes side views of an exemplary set or assemblage of scribing end centering guides.

#FIG. 3 is a sectional view as indicated in FIG. 1.

#Referring now to the drawings, and in particular to FIG. 1, a hollow bored stylus retaining quill 2 has knurling 3 upon its annular outer surface, the knurling facilitating slip free manual handling. An apertured cap 4 is fixedly and removedly attached to the upper end of the stylus retaining quill 2, preferably by means of, referring to FIG. 3, spiral threading 6. Referring again to FIG. 1, the apertured cap 4 has a knurled surface 8 for non-slip turning and counter-turning for cap removal and cap attachment.

#Referring simultaneously to FIGS. 1 and 2, an exemplary {fraction (11/16)}″ scribing end centering guide is designated by reference arrow 10. Referring to FIG. 1, said guide 10 is interchangeably attachable to the lower end of stylus retaining quill 2. The lower end of said scribing end centering guide 10 is preferably circularly configured for insertion into common {fraction (11/16)}″ diameter apertures of drilling templates. For ease of insertion and extraction of the lower end of such scribing end centering guide 10 into such {fraction (11/16)}″ (or 0.6875″) circular aperture, the true outside diameter of such guide is preferably milled to 0.687″, allowing for free sliding insertion into such aperture.

#Referring simultaneously to FIGS. 2 and 3, the scribing end centering guide 10 is preferably configured as a quill having a hollow bore 12. Suitably, the lower end of scribing end centering guide 10 may be configured other than circularly so long as such end presents bearing surfaces sufficient for centering within a circular aperture of a drilling template.