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A Precision Scribing and Lofting Table

A Precision Scribing and Lofting Table MARKlNG-OFF A Precision Scribing of the vernier cursor. With the scribing of lines at right angles to the central datum, vernier and Lofting Table gauges are applied to the longitudinal locating pins and the settings are dictated by the number of stations and the pitches required. Should the Details of a Piece of Equipment Developed pitch of the stations be 12 in. or factors of 12 in., by Short Bros. and Harland Ltd. i.e. 3, 4 or 6 in pitch,the marking out process is further simplified by the fact that re-setting of the vernier gauges is considerably minimized. PRECISION Scribing and Lofting Table, verse scales, linear readings to 1/1000 of an inch Lines inclined to the datum can be scribed in which provides an accurate mechanical can be registered. a similar manner. Knowing the angle, reference A means whereby layout and lofting processes In one application, two vernier gauges are pro­ can be made to the sine chart which gives the can be performed to close tolerances in the mini­ vided which operate on opposite sides or ends of corresponding offset to which the vernier gauges mum of time, has been developed by Short Bros. the table. Rectangular steel bars 1 in. xi in. are must be set on opposite sides of the table. The & Harland Ltd. fitted to the sides and ends of the table; i in. straight edge position against the locating pins The device is based on the principles of the diameter pins (the holes for which are jig bored) will give the required angle, and with the aid of vernier height gauge and sine-bar and has their are pitched at 12 in. intervals along the bars for linked parallels, the line can be scribed through advantages. It provides accuracy in lofting with locating the vernier gauges. Pins on opposite ends any desired point. claimed overall saving of time of at least 60 per cent and sides must be directly in line with each other. Similarly, the set square can be projected from on both layout and inspection functions; reduc­ The transverse pitch between the centres of the the straight edge to give a line at right angles to tion of error due to progressive build up on a big pins on the longitudinal members is accurately the base line. Spring clamps are provided for layout, and the elimination of errors in calcula­ set at 50 in. This provides a 'constant' by virtue securing the vernier gauges to the table and are tions. The use of trammels for bisecting of lines of which the amount of offset between the read­ for use in cases where the verniers are intended is eliminated, their use being confined to the ings of the vernier gauge on one side and the to be stationary for prolonged periods. scribing of arcs of circles. reading of the vernier gauge on the opposite side A modified version of this table is shown in Equipment of this kind helps to ensure the can be predetermined for any required angle. On FIG. 1. In this case, the fixed locating pins are high degree of accuracy, consistency and surface- this basis a Chart has been compiled from which dispensed with, steel bars being fitted with measur­ finish required by high-speed aircraft today. The the offsets for all angles between 0 to 45 deg. in ing scales marked in 1 /20th of an inch and cover­ increments of one minute of arc are given; thus determination of the standard of finish is largely ing the full length and width of the table on all any required angle up to 360 deg. can easily be dependent on structural accuracy which, in the four sides. An independent cursor, similar in catered for. main, is achieved through the medium of layouts design to that already described is fitted to each and templates. Jn fact, with the use of full scale The vernier gauges are provided with locating scale, a 4 in diameter locating pin fulfilling the lofting, together with the Lithographic reproduc­ holes, jig bored to exactly 12 in. apart and fitted same function of locating the straight edge as tion process now being used by many aircraft with hardened steel bushes to pick up on the previously described. companies, the standard of tooling, and ulti­ locating pins. The blade carries a 14 in. scale The distinctive feature of this design is that the mately the finished product, arc determined at graduated in I/20th of an inch, the zero marking fixed locating pegs and the bush holes of the the basic lofting stage. of which corresponds to the inner face of the vernier scales of the original design are dispensed Present-day trends arc towards increased use of hardened steel bush. The vernier cursor is grad­ with, providing a decided advantage in manipula­ uated to read in thousandths of an inch and the templates and layouts for all kinds of jig making, tion and accuracy of setting in cases where the hardened steel ■} in. diameter pin is placed as to be including, in particular, envelope jigging as it table is being permanently employed as an inde­ axially in line with the bush, as are also the fixed applies to major aircraft components. pendent unit (i.e. unattached to any other layout steel locating pins, when the vernier is at the There is, therefore, a growing need for machine table). In every other respect, the table has similar zero position. By application of the verniers to tools capable of machining simple and com­ features to the No. 1 design and serves exactly any pair of locating pins, measurements up to plicated profiles by the use of automatic devices the same function. 10 ft. in thousandths of an inch can be made working from templates. There arc many machines longitudinally, and 4 ft. transversely. capable of this work, but in many instances the products depend for their accuracy on the shape In performing the marking out functions, the of a template. material is clamped to the table using four clamps It was in the light of these developments and which permit unrestricted movement of the the increasing application of templates and lay­ verniers. Assuming that the longitudinal centre line or datum is to be scribed, the verniergauges outs to the manufacturing process that considera­ are applied, on the central position, to opposite tion was given to the possibility of developing a method whereby precise mechanical means ends of the table with the vernier cursor set as could be made available for the purpose of mark­ zero. The straight edge is then located against the ing out basic grillages, offsets and the like, with pegs, automatically bringing the edge of the the precision of a vernier height gauge. straight edge in line with the zero markings of the scale and vernier, following which the required Base grillage can be marked off at stations and line can be scribed or drawn. offsets at any required pitch, either parallel or at right angles to one another, or at any required Lines. parallel to the central datum can be angle within a minute of arc up to 360 deg. with­ marked in a similar fashion at any required pitch out recourse to calculations. By virtue of the by the combined movement of the vernier gauge vernier cursors on the longitudinal and trans­ from one set of pegs to another and the re-setting 176 Aircraft Engineering http://www.deepdyve.com/assets/images/DeepDyve-Logo-lg.png Aircraft Engineering and Aerospace Technology Emerald Publishing

A Precision Scribing and Lofting Table

Aircraft Engineering and Aerospace Technology , Volume 25 (6): 1 – Jun 1, 1953
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Publisher
Emerald Publishing
Copyright
Copyright © Emerald Group Publishing Limited
ISSN
0002-2667
DOI
10.1108/eb032302
Publisher site
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Abstract

MARKlNG-OFF A Precision Scribing of the vernier cursor. With the scribing of lines at right angles to the central datum, vernier and Lofting Table gauges are applied to the longitudinal locating pins and the settings are dictated by the number of stations and the pitches required. Should the Details of a Piece of Equipment Developed pitch of the stations be 12 in. or factors of 12 in., by Short Bros. and Harland Ltd. i.e. 3, 4 or 6 in pitch,the marking out process is further simplified by the fact that re-setting of the vernier gauges is considerably minimized. PRECISION Scribing and Lofting Table, verse scales, linear readings to 1/1000 of an inch Lines inclined to the datum can be scribed in which provides an accurate mechanical can be registered. a similar manner. Knowing the angle, reference A means whereby layout and lofting processes In one application, two vernier gauges are pro­ can be made to the sine chart which gives the can be performed to close tolerances in the mini­ vided which operate on opposite sides or ends of corresponding offset to which the vernier gauges mum of time, has been developed by Short Bros. the table. Rectangular steel bars 1 in. xi in. are must be set on opposite sides of the table. The & Harland Ltd. fitted to the sides and ends of the table; i in. straight edge position against the locating pins The device is based on the principles of the diameter pins (the holes for which are jig bored) will give the required angle, and with the aid of vernier height gauge and sine-bar and has their are pitched at 12 in. intervals along the bars for linked parallels, the line can be scribed through advantages. It provides accuracy in lofting with locating the vernier gauges. Pins on opposite ends any desired point. claimed overall saving of time of at least 60 per cent and sides must be directly in line with each other. Similarly, the set square can be projected from on both layout and inspection functions; reduc­ The transverse pitch between the centres of the the straight edge to give a line at right angles to tion of error due to progressive build up on a big pins on the longitudinal members is accurately the base line. Spring clamps are provided for layout, and the elimination of errors in calcula­ set at 50 in. This provides a 'constant' by virtue securing the vernier gauges to the table and are tions. The use of trammels for bisecting of lines of which the amount of offset between the read­ for use in cases where the verniers are intended is eliminated, their use being confined to the ings of the vernier gauge on one side and the to be stationary for prolonged periods. scribing of arcs of circles. reading of the vernier gauge on the opposite side A modified version of this table is shown in Equipment of this kind helps to ensure the can be predetermined for any required angle. On FIG. 1. In this case, the fixed locating pins are high degree of accuracy, consistency and surface- this basis a Chart has been compiled from which dispensed with, steel bars being fitted with measur­ finish required by high-speed aircraft today. The the offsets for all angles between 0 to 45 deg. in ing scales marked in 1 /20th of an inch and cover­ increments of one minute of arc are given; thus determination of the standard of finish is largely ing the full length and width of the table on all any required angle up to 360 deg. can easily be dependent on structural accuracy which, in the four sides. An independent cursor, similar in catered for. main, is achieved through the medium of layouts design to that already described is fitted to each and templates. Jn fact, with the use of full scale The vernier gauges are provided with locating scale, a 4 in diameter locating pin fulfilling the lofting, together with the Lithographic reproduc­ holes, jig bored to exactly 12 in. apart and fitted same function of locating the straight edge as tion process now being used by many aircraft with hardened steel bushes to pick up on the previously described. companies, the standard of tooling, and ulti­ locating pins. The blade carries a 14 in. scale The distinctive feature of this design is that the mately the finished product, arc determined at graduated in I/20th of an inch, the zero marking fixed locating pegs and the bush holes of the the basic lofting stage. of which corresponds to the inner face of the vernier scales of the original design are dispensed Present-day trends arc towards increased use of hardened steel bush. The vernier cursor is grad­ with, providing a decided advantage in manipula­ uated to read in thousandths of an inch and the templates and layouts for all kinds of jig making, tion and accuracy of setting in cases where the hardened steel ■} in. diameter pin is placed as to be including, in particular, envelope jigging as it table is being permanently employed as an inde­ axially in line with the bush, as are also the fixed applies to major aircraft components. pendent unit (i.e. unattached to any other layout steel locating pins, when the vernier is at the There is, therefore, a growing need for machine table). In every other respect, the table has similar zero position. By application of the verniers to tools capable of machining simple and com­ features to the No. 1 design and serves exactly any pair of locating pins, measurements up to plicated profiles by the use of automatic devices the same function. 10 ft. in thousandths of an inch can be made working from templates. There arc many machines longitudinally, and 4 ft. transversely. capable of this work, but in many instances the products depend for their accuracy on the shape In performing the marking out functions, the of a template. material is clamped to the table using four clamps It was in the light of these developments and which permit unrestricted movement of the the increasing application of templates and lay­ verniers. Assuming that the longitudinal centre line or datum is to be scribed, the verniergauges outs to the manufacturing process that considera­ are applied, on the central position, to opposite tion was given to the possibility of developing a method whereby precise mechanical means ends of the table with the vernier cursor set as could be made available for the purpose of mark­ zero. The straight edge is then located against the ing out basic grillages, offsets and the like, with pegs, automatically bringing the edge of the the precision of a vernier height gauge. straight edge in line with the zero markings of the scale and vernier, following which the required Base grillage can be marked off at stations and line can be scribed or drawn. offsets at any required pitch, either parallel or at right angles to one another, or at any required Lines. parallel to the central datum can be angle within a minute of arc up to 360 deg. with­ marked in a similar fashion at any required pitch out recourse to calculations. By virtue of the by the combined movement of the vernier gauge vernier cursors on the longitudinal and trans­ from one set of pegs to another and the re-setting 176 Aircraft Engineering

Journal

Aircraft Engineering and Aerospace Technology – Emerald Publishing

Published: Jun 1, 1953

There are no references for this article.