US2393094A - Gauge for steep faced threads - Google Patents

Description

- Jan. l5, 1946. R. T. PENN GAGE FOR STEEP FACED THREADS Filed March 28, 1944 2 sh'eets-sheet 1 Patented Jan. 15, 1946 UNITED `STATES PATENTY lOFFICE GAUGE' FOR STEEP FACED' THREADS' Raymond-1L T. Fenn, Springfield; V-t., assignor to Bryant Chucking. Grinder Company, Springfield, Vt., a.- corporation of Vermont Application MarchrZS, 19445, Serial No. 528,399

(Cl. 33e-199) 3. Glaims.

When. gauging. threads, gaugingI anvils which mate the, threads to be gauged are. employed. WhenA th'e work. has a. thread' provided with a steep face, as for example, a buttress thread where one face of the thread formis-SOF or nearly 90' to the work axis, the tolerance with. respect to this angle is extremely small, and' it isextremely diicult to machine a, conventional form ofanvil to this form. Such a conventional. form for.' outsidegauging would. be a segment of an internally'threaded piece which. consequently has a concave periphery for engagement with the con-` Vex` periphery of, the work piece.. It. is impracti'cabl'e to; grind the steep face of the thread. form in an internally threaded hole to the close tolerances required for gauging.

In accordancewith this invention, therefore, adilerent type. of' anvil is` employed, this being provided with externally formed gauging elements. Thread rolls might be. employed for such.

necessity makes this. type ofv anvil undesirable,

and to avoid this, instead of helically threaded rolls, in accordance with this invention. annularly grooves rolls are employed and they are spaced axially ofV the` work, each one to its succeeding one byan amount equal to the lead of the thread between the pointsof contact of. the several rolls determined by their angular spacingV about the work.. The use of annular grooved rolls, however, maygive rise to a. region of interference with the steep faces of the threads of the work because of' th'e factA that the annularly grooved roll has no. lead; Ifsuch a roll is tilted to the. helix angle, this interference will be eliminated, but a. full contact throughout the length of thev roll. will not be obtained since the axes of the workpiece and' roll do not thenI lie in acommon plane. In order'to obtain such a full' length contact, in ac.- cordance withl thisv invention, a conical roll. is

used, the conical roll being tilted toward the axist of the work so as to bring its small endinto vgauging position in linewith the larger end.

parallel to aline through successive corresponding points in the thread periphery lengthwise. of the work. This tilting` of the conical roll causes th'e axesof. the roll and the work piece to lie in substantially acommon plane in which these axes are not parallel. Substantially where. this. plane intersectsthe peripheries ofthe work piece and theroll;,the steep: faces of' the roll engage the steep faces' of' properly formed work threads throughout the axial length common toboth pieceand roll. The tilting of the gauge roll'y axis causes its steep gauging faces, which are. per.-

pendicular to its axis, to be inclined to planesv perpendicular to the axis of the work, and as these gauge faces recede in opposite directions away from the common plane of the two axes; they also separate from the perpendicular work faces. Due to the lead of the threads, the steep faces of the work also are inclinedto planes perpendicular to the work axis, this inclination being inamount the lead angle of th'e threads. and on one side ofthe common plane of rtheaxes, this inclination is in the same direction as the inclination ofthe conicalgauge roll steep faces. If this inclination of the gauge faces. is slightly greater than that of the work faces, which Vis insured by making the roll taper slightly more than the helix angle, the permissible minimum cientlymore than the helix angle of the thread, as hereinbefore specified., interference on the steep face of the thread and rolls is eliminated, and.

this taper may be larger th'an this` limit so long as itis not sufliciently great to cause interference on the inclined faces of the threads. A slight excess of the taper ofl the rol1f over the lead angle is necessary to insure that contact between the gauging 'anvils andA steep thread faces4 occurs in the plane containingjthe axes of the work piece and anvil, this excess providing. for clearance elsewhere and to allow fory inaccuracies in that planev to.` elect the gauging action to at least. slightly outside ofthe tolerance limits desired for the gauge indication. As the inclined facesA cf. the

threads and gauging ridges recede rapidly from each other from the pointsoi maximumcontact,A no interference on these facesv is to be expected,

provided. these inclined' faces are not. too steep, and th'e angle of taper and tilt doesnot. greatly exceed the lead angle ofthe threads. In all cases the direction of taper, that is toward the smaller diameter end; of the. gauging anvilsV is inthe. di-

rection from. the inclined towardithe steep facesof each thread valley. For this reason a single For a more complete understanding of this in# and a washer 28 is placed between its upper end and the head 29 of the screw. The inclination of the axis of each of the anvils toward the axis of the work piece is such as to bring into parallelism the adjacent generating elements of the two surfaces of revolution generally defined by the roll and by the threaded surface of the work, the extent of angularity of the mounting being equal to that of the taper when gauging straight th'reads or equal to the sum or difference of the tapers for Vthe roll and tapered threads when gauging tavention, reference may be had to the accompany y ing drawings, in which Figure 1 is a top plan View, partly broken away Figure 2 is a sectional view on line 2-2 of Figure 1.

Figure 3 is a view somewhat similar to a portion'of Figure 2 to a. larger scale and showing one of the gauging anvils in central section. Figure 4 is a fragmentary perspective view showing a modified construction of gauging anvil.

Figure 5 is a fragmentary view to a larger scale showing the anvil in elevation andthe work in section. Y

, Figure 6 is a detail sectional view on line 6-6 ofFigure5. Y Y

Figures 7 and 8 are side and end elevations, respectively, of a snap gauge for buttress threads.

Figure 9 is a view similar to a portion of Figure l, but showing a gauge for use with squareor substantially square threads. i

,Figures 10, l1 and Vl2 are detail sectional views on the correspondingly numbered section vlines of Figure 9, Figures 1l and 12 being drawn to a larger scale. I Y

Referring to the drawings, a work piece provided with buttress threads is sh'own at I, this being illustrated as engaged with a tubular holder 2 supportedona platform 3, this platform having a depending portion 4 supported fromthe bed 5 as by spring elements E, the upper ends of which are outwardly turned` and engaged in slots .in stationary members 'IWhich form a part of the bedr 5. .These springs 6 permit some lateral motionj of th'eiwork to bring it into or out of contact with a pair of fixed gauging anvils I0 carried by the bedS.v This support also permits a sufficient vertical adjustment of the work so that its threads may be brought intov proper relation to the gauging Yelements of theanvils. A movable gaugingV anvil II is shown as supported on an arm I2 plv-- oted as by pairs of cross springs I3 and I4 on a stationary supporting post I5. The movable an-v vil ,II may be pressed toward the fixed anvils as by a spring I6 reacting between an arm I 'I secured to the arm I2 and a fixed abutment I8, and the position of the gauging element when in gauging position may be shown by a position indicator at having a stem 2I against which the arm I2 contacts, the position indicator 20 being supported in ,fixed position by the bed 5, as shown in Figure 2. This general arrangement of xed and movable anvils withfthe indicator controlled by the position of the movable lanvil is not my invention, which is concerned with the gauging elements per se and their relation to each other.

It will` be noted that each of the gauging elements as shown in Figures 1, 2 and 3, is a tapered roll i which'is held on a central support as by ascrew 26, the upper end of which is inclined toward the central axis of the work. As shownV the gauging anvil 25 isprovided with a central bushing 21 through which the screw 26 extends pered threads, and in order that there shall be no interference between the steep faces 3l of the work'an'd the corresponding steep faces 32 of the anvil', this 'angle must be at least as much as the helix angle of the work threads being gauged. The engagement between the steep thread faces of the work and the corresponding faces of the anvil is shown best in Figure 6. The lines e-e represent the steep thread faces, being at angles 0, representing the `lead angles, to the lines f-. perpendicular to the work axis fte-h. The curved lines g-g show the apices of the iiat gauging faces of thegauging anvil ribs which are shown as elliptical lines since theyare arcs of circles viewed nearly edgewise at the `angle of tilt, but they are nonsymmetrical with relation to the thread faces e-e since, as these gauging faces are peripheral ribs instead of threads, they have 84 for gauging work threads of 90.

no lead. The smaller the amount of tiltof the anvils is made, approaching the lead angle, the atter these curves become, approaching the lines f-f, but anything less than the lead angle brings the lines g-g below the lines e-eto the left of the axis h-h, representing interference between the anvils and the work which, of course, would render the gauge inoperative for correct gauging. It will be noted that if the steep face of the work thread is to the work axis, this tilting of the anvils causes the steep faces of the anvilsto be less than 90 by the amount Yof tilt. Thus assuming that the angle of tilt a is 6, the angle of the steep faces of the gauging elements will be This `de crease of the 'angle of the steep thread faces for the anvils which is illustrated clearly in FigureV 5 makesit possible to grind these steep faces'. accurately; If the steep faces of the work are at less than a 90 angle, all the more decrease'i angle is'provided for the anvil steep faces.

It will be noted from an inspection of Figure 2, that the two anvils there shown are spacedaxially by an amount equal to the lead of Ythe thread between. the gauging points of contact. Thus the right vhand fixed anvil shown in Figure 2 is shown as mounted somewhat lower than the movable anvil Il. The third anvil is similarly axially oifset from the others in accordance with the lead between these points of contact. i

In Figure a modifcation'is shown in which instead of employing a complete conical gauging anvil, the anvil comprises a segment slightly less than one-third of the complete circumference. This permits one roll to be cut into three segments, each of which may be used where three anvils are to be employed for gauging a single piece as will usually be provided.

In Figures 7 and 8 the invention is shown as embodied in a snap gauge, the gauging anvils 50,

being formed and spaced to pass work within the maximum tolerancelimits, and the anvils 5I being formed and spaoedto pass work just belowminimum tolerance limits, the anvils 5I) thus being` go Vanvils and `the anvils 5II being not go anvils. l

It will be noted that a set of anvils for gauging work having steep faces on one side cannot at the same time gauge steep faces on the opposite sides of the threads. Thus, if it be desired to gauge square or nearly square threads, anvils shaped to gauge one steep face and with clearance for the other steep face may be used, and provided the threads t-o be gauged are symmetrical, the work may be subjected to two gauging operations with the work facing in opposite directions. Square or'nearly square threads may be gauged in a single operation, however, by employing two sets of oppositely facing anvils, one set for each steep face, in which case opposite thread faces need not be symmetrical if the anvils are shaped to the particular faces to be gauged thereby.

A gauge for gauging square or nearly square threads in a single operation with two sets of anvils is shown in Figures 9 to 12, inclusive. Referring to these iigures, two sets of stationary anvils 6D and 'Bl are employed and one set of movable anvils B2 and 63. Each of the sets of anvils is carried by one end portion of a lever r64 or `(i5 fulcrumed centrally at 66 and 61, respectively. The two anvils of each set are reversely disposed, that is, one of the anvils yBIJ is mounted with its small end upward as shown at the left hand in Figure 10 and its axis is inclined upwardly and inwardly, while the other anvil 6| at the right as shown in Figure 10, is arranged with its larger end upwardly and its axis inclined upwardly and outwardly. The anvils 60 engage the upper steep faces of the square threads 19 of the work as shown in Figure 1l, while the anvils ylil engage on the lower faces of these threads 1! as shown in Figure l2, the gauging ribs of each of these anvils being cut away on the side opposite to the steep gauging faces to clear the oppositely disposed steep faces of the threads. The anvils of each set are offset axially of the Work in accordance with the lead advance between them determined by their angular relationship as in the case of the gauge provided with the single set of anvils shown in Figures 1 to 4 and 8. Since these two sets of anvils are pivoted for free equalizing motion from and toward the worky and the anvils for gauging each side of the work thread are symmetrically disposed, the anvils cooperate with each other to produce a true gauging action. The peripheral edges of the gauging ribs of the anvils may be formed to engage the Work at the roots of the threads, and the side faces of the anvils between the gauging ribs may be formed to engage the outer faces of the threads, so that between the two sets of anvils gauging of substantially the entire thread faces is produced; The anvils 62 and 'B3 are mounted on the eoualizins lever 65 carried by the movable arm I2 of the gauge in place of the single gauging element shown in Figures 1 and 2, and the gauging action may be produced similarly as by means of a position indicator as shown in Figures 1 and 2.

While as shown the anvils are arranged-for gauging external straight work, similar anvils may be used for gauging internal work or taper threaded Work, if desired. In gauging internal work, the curvature of the work and of the anvils is in the same direction, so the anvils should be of as small diameter as is practicable in order that they may be given sufficient motion for free gauging action without interference. In gauging taper threads the inclination of the anvil axes will be modied to suit the taper of the work so as to bring the gauging portions of each anvil from end to end into the same relation to standard work threads.

It also will be evident from the foregoing description of certain embodiments of the invention that other changes and modifications might be made without departing from the spirit or scope of this invention as defined by the appended claims.

I claim:

i. A gauge for threads having at least one steep face, said gauge including a plurality of relatively movable gauging anvils, each of said anvils including at least a portion of an annularly grooved roll tapered at an angle greater than the lead angle of the threads to be gauged, each of said grooves having one face for engagement with the steep face of the threads and said anvils being offset axially of the Work relative to each other by amounts equal to the thread lead for the angular distance by which said anvils are spaced about the axis of the work, said roll portions being tilted to bring the line of gauging action parallel to a line through successively corresponding points of the thread peripheries lengthwise of the work substantially in a plane containing the axes of the threaded work and of the tapered roll.

2. A gauge for threads having at least one steep face, said gauge incluing a plurality of relatively movable gauging anvils, each of said anvils including a fixed peripheral segmental portion of an annularly grooved roll tapered at an angle greater than the lead angle of the threads to be gauged, each of said grooves having one face for engagement with a steep face of the threads and said anvils being offset axially of the work relative to each other by amounts equal to the thread lead for the angular distances by which said anvils are spaced about the aXis of the work, the axes of said roll portions being tilted to the work axis at the taper angle to bring the line of gauging action parallel 'to the thread peripheries lengthwise of the work substantially in a plane containing the axes of the threaded work and of the tapered roll.

3. A gauge for threads having opposed steep thread faces, said gauge including a pair of sets of relatively movable gauging anvils, each of said anvils including at least an arcuate portion of an annularly grooved roll tapered at an angle greater than the lead of the threads, the anvils of the two sets being disposed with their smaller diameter ends facing in opposite directions and inclined toward the work to engage correctly shaped work threads equally from end to end of the gauging portions of said anvils, each of said anvils having one wall of each groove shaped to engage oneside wall of a work thread and the opposite wall free from engagement with the opposite wall of the work thread valley, anvils of the two sets engaging opposite steep faces of the work threads and positioned alternately about a central axis in pairs including an anvil of each set, and a pivoted lever to which the anvils of each pair are secured permitting said anvils of the two sets to automatically adjust themselves to the threads of the work when said anvils are moved relatively into gauging relation to such work, the anvils of each set being offset axially of the work relative to each other by amounts equal to the thread lead for the angular distances by which said anvils are spaced about the axis of the work.

' RAYMOND T. FENN.

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