Thread Angle Research Articles

Stress in bolt and nut (Effects of contact condition at the first ridge)

Effects of the contact condition at the first ridge on mechanical behaviors of threaded portions are analysed by an axi-symmetric FEM which can deal with the three-body elastic contact problem including the effects of friction on two contact surfaces between threads of bolt and nut, and between fastened plate and nut. Since the cross sectional shape of nut at the first ridge changes circumferentially due to the lead angle of thread, it causes non-symmetric mechanical behaviors concerning the ratio of flank load and the stress concentration at the root of bolt. Four types of models are used to estimate these non-symmetric properties approximately. Each of them represents the cross section rotated one fourth revolution around the axis. The analytical object is composed of bolt, nut and fastened plate, and only the shape of nut is changed. The analysis is done by the axi-symmetric FEM ignoring the effects of lead angle. The ratio of flank load and the stress concentration at each cross section show some remarkable effects of the non-symmetric behaviors.

Stresses in Bolt and Nut : Effects of Contact Conditions at the First Ridge

Effects of the contact condition at the first ridge on mechanical behaviors of threaded portions were analysed using an axi-symmetric FEM which is appropriate for the three-body elastic contact problem including the effects of friction on two contact surfaces between threads of bolt and nut, and between fastened plate and nut. The cross sectional shape of nut at the first ridge changes circumferentially due to the lead angle of thread, which causes non-symmetric mechanical behaviors concerning the ratio of flank loads and the stress concentration at the root of bolt. Four types of models were used to estimate these non-symmetric behaviors approximately. Each of them represents the cross section rotated one fourth revolution around axis. The analytical members are bolt, nut and fastened plate, and only the shape of nut is changed. The analysis is done by the axi-symmetric FEM without considering the effects of lead angle. The ratio of flank loads and the stress concentration at each cross section show some remarkable effects of the non-symmetric behaviors.

ねじの三針法測定における針とねじ面との単一接触限界について

In the measurement of screw threads by the three-wire method, the measuring cylinder placed in the thread groove should touch the opposite each thread flanks of the groove at one point respectively. It is necessary to consider in detail the conditions for single contact between the cylinder and each thread flank because many threads with small included angle of thread and large lead angle cannot be measured with thread-measuring cylinders due to double contact between cylinder and thread flank. This report deals with a simple approximation formula and precise formula for determining when double contact between the cylinder and thread flank occurs. In order to make practical determination easier, a simple approximation formula for the limiting condition for single contact is derived. However, by reason of the approximate nature of the formula, double contact does not necessarily occur when the approximate formula is not satisfied. Therefore a more detailed analysis for single contact is required in this case. As the result, a precise formula for the limiting condition for single contact is derived by an analytical me thod.

Stabilimenta on the webs of Uloborus diversus (Araneae: Uloboridae) and other spiders

Uloborus diversus places extra silk (“stabilimenta”) near the hubs of its webs, preferentially on short radii ending near anchor threads. Spiders probably distinguish these radii from others by their relatively low extensibility. The stabilimentum probably functions as a camouflage device, and the orientation of the stabilimentum lines probably aids disturbed spiders in making quick exits from webs. Turning responses at radius‐frame junctions during these exits are influenced by thread angles at the junctions (and possibly by other factors), and also enable disturbed spiders to reach hiding places quickly. The available data on other stabilimentum‐building spiders suggests that they also use stabilimenta to provide defence against visually‐hunting predators.

Colonofiberoscopy: Technique in Colon Examination

The flexible fiberoptic colonoscope has a proximal observation lens for the viewer. This lens is connected by thousands of fiberglass threads to the distal lens at the tip of the colonoscope. Transmission of an image through the fiberglass threads permits clear upright viewing of any adequately illuminated field at a distance of from one centimeter to many meters away and in either a straight or curved line. Cold light from an electric power source is transmitted by another set of fiberglass bundles in the colonoscope. As with the image transmission, the cold light can be transmitted with intensity at distances up to many meters along any angle of the fiberglass threads. A study of fiberoptic endoscopic techniques applied to the colon was initiated in the surgical endoscopy unit at the Beth Israel Medical Center in June 1969 when the instrument first became available. Between June 1969 and June

The Effect of Thread Angle on Loosening by Impact : 1st Report, Theoretical Analysis

The purpose of this research is to find out a certain angle of the thread unloosening under repeated impacts. In the last report(2), the author described the general theory of fastening and loosening process of screw threads qualitatively. In this report, he induces theoretical formulae by using a three-dimensional analytical geometry to make clear the effect of thread angle on loosening quantitatively. He performed numerical calculations on 10 metric screw threads used popularly by changing their thread angle from 65° to 55° and obtained the following conclusions. (1) When the pitch-diameter ratio is 0.15 (M8, M10, M12, M14), 0.125 (M16, M8×1, M10×1.25) or about 0.1 (M12×1.25, M14×1.5, M16×1.5) and thread angles are 63°, 62.5° or 62° respectively, the strongest fastening action is obtained for each of them. These screw threads are insensitive to angle error. (2) When the thread angle is 60° or 55°, a comparatively strong loosening action is obtained.

The Effect of Thread Angle on Loosening by Impact : 1st Report, Theoretical Analysis

The Effect of Thread Angle on Loosening by Impact : 1st Report, Theoretical Analysis

Correction for angle of helix pitch in measurements of pitch diameter of an asymmetric thread

1. The most accurate value of the correction for the helix angle of an asymmetrical thread is given, after Eq. (11), by Eq. (15), which can be applied to calculations of corrections in the case of almost all standard but-tress threads. 2. Calculations of the correction based on Eq. (11), using the method of successive approximations, can be recommended only for application to asymmetrical threads with a helix angle greater than 7°, considering the cumbersome nature of the computation work involved, and can also be recommended in those cases where the value of the correction is in excess of 0.1 mm. 3. The procedure advanced here for determining corrections could be advantageously incorporated into the standard GOST 12734-67 when that standard is revised.

Loosening by Repeated Impact of Threaded Fastenings

It is common experience that nuts and other threaded fasteners can be loosened by vibration or by impact even though they are initially tight. This report proves that a threaded fastener is hard to loosen when the angle of thread and the measurement of the screw end are properly chosen. The fastener with 60 deg. V thread is easy to loosen. Because the compressive stress waves, being propagated from the pressure falnk, are reflected at the free end of the screw, when they change into tensile stress waves, and they return to the pressure flank on the bolt side only. So a threaded fastener becomes hard to loosen, when the tensile stress waves don't return to the pressure falnk of the bolt thread. On the following two occasions, the tensile stress waves don't return to the pressure flank. (1) When the tensile stress waves are propagated towards the unthreaded part of the bolt. (2) When they are reflected back to the pressure falnk being changed into compressive stress weves.

A study on tapping wrought aluminum (1st Report)

The tapping (tapping for screwing) test for wrought aluminum alloys is reported in th paper. Three sorts of alloys, or 17S and 24S as typical alloys of high tensile strength and 56S as an anticorrosion alloy, were examined for tapping machinability such as tapping resistance, state of rough surface, accuracy of finished surface, etc.The results obtained were summarized as follows.The tapping torque was not affected by cutting speed of 5-10m/min in this experiment, but the torque at a constant rake angle slightly increased with the increase in tapping load. The torques varied according to the sorts of materials. Their values were arranged in ascending order of 24 S-F, 17 S-F, and 56 S-F, among which 24 S-F gave the most stable value, while the latter two gave unstable ones, having large deviation. It seemed that the state of finished surface was dependent upon rake angle and tapping load, but was independent of cutting speed; and there would be found out optimum tapping conditions for obtaining the best surface state. It was observed that the pitch of thread agreed with the tap within the limit of ever in measurement regardless of tapping conditions, and the angle of thread was larger by 30-60' than that of tap. The value of microhardness tended to increase up to about Hv=10-20 in the neighborgood of tapped surface.

CONTROL OF DRAFTING BY AIR FALSE TWISTER (II)

In the preceding paper (I), the ability of air twister tube as a substitute for usual twister tube of woollen ring spinning frame was studied.The effects of draft ratio, air pressure and tube dimension on false turns were experimented.The same testing apparatus as in the preceding paper was used in this experiment. The relation between irregularity of sliver and drafting condition-tube position, ratch, thread angle, etc-was investigated. The experimental results suggest the capability of the high drafting of condensed slubbing.The results obtained are as follows.1. The irregularity of slubbing drafted by using air twister tube has the same order as usual false twister. (Figs. 3, 4) These results substantiate the possibility of air twister.2. The tube setting should be decided by fiber length of the condensed slubbing. Each curve of Figs. 5 and 6 has a minimum value at the point of the longest fiber. Getting the ratch short, the irregularity is slightly reformed, and so, the long ratch as the woollen mule spinning is not necessarily reasonable. (Fig. 7)3. Applying air false twister, drafting with 2_??_3 zone is able to draft higher the woollen slubbing than usual single zone. In this case, the draft ratio of each zone should be limited within the range of CVa/CVb<1.

CONTROL OF DRAFTING BY AIR FALSE TWISTER (1)

In the preceding paper (I), the ability of air twister tube as a substitute for usual twister tube of woollen ring spinning frame was studied.The effects of draft ratio, air pressure and tube dimension on false turns were experimented.The same testing apparatus as in the preceding paper was used in this experiment. The relation between irregularity of sliver and drafting condition-tube position, ratch, thread angle, etc-was investigated. The experimental results suggest the capability of the high drafting of condensed slubbing.The results obtained are as follows.1. The irregularity of slubbing drafted by using air twister tube has the same order as usual false twister. (Figs. 3, 4) These results substantiate the possibility of air twister.2. The tube setting should be decided by fiber length of the condensed slubbing. Each curve of Figs. 5 and 6 has a minimum value at the point of the longest fiber. Getting the ratch short, the irregularity is slightly reformed, and so, the long ratch as the woollen mule spinning is not necessarily reasonable. (Fig. 7)3. Applying air false twister, drafting with 2_??_3 zone is able to draft higher the woollen slubbing than usual single zone. In this case, the draft ratio of each zone should be limited within the range of CVa/CVb<1.

ROLLER DRAFTING OF CONDENCED SLUBBINGS

A tester (Fig. 1.) was designed to measure the torque and tension generated when the slubbing is twisted under a constant length or constant tension.Using this tester, the mechanism of false twisting system, which controls drafting by frictional twisting between twister tube and slubbing, was investigated. Some results are shown in Fig. 2_??_Fig. 6.The twist turns which are inserted is decided by the balance between the moment of false twister and the torque of sliver. These relation were analyzed theoretically in equations (4)_??_(7). The theory is applied to the results of the experiment on thread angle and sliver thickness in the preceding pa_??_er (V).

ROLLER DRAFTING OF CONDENCED SLUBBINGS

The effects of twister tube wihich seems very important for roller drafting of condensed slubbing are investigate.A tester (Fig.1) has been designed to draft condensed slubbings by roller drafting type under various conditions of draft ration, ratio, ratchm false twister speed and thread angle θ (angle between slubbing and center of twister tube), and to measure the tension generated.The reduction in weight percentage of the cendensed slubbing takes place within the drafting field, mainly in the proximity of the front roller inside the tube, and slightly at the back roller. (Fig.4_??_Fig.7) These two parts have less number of turns of false twist than in the other part. (Fig.8_??_Fig.9)The efficiency of false twister tube is high at slow speed, and low at high speed. (Fig.10)

ON THE FRICTION OF THE THREAD WITH RIGIDITY

The frictional behaviours of the thread wrapped around cylinder have been studied with a consideration on the flexual rigidity of thread. Firstly, assuming that the thread is a completely elastic body and the coefficient of friction between the thread and cylinder is constant, the studies were extended to general thread.1). Basic Equation (Fig. 2)where, T0, T1; thread tension acting at the contact end, F0 F1; reactive force acting at the contact end against cylinder, μ; coefficient of friction between thread and cylider, θ; contact angle of thread wrapping a round the cylinder.2). General case (Fig. 3)Using equation (a), the following is obtained.where, t0, t1; thread tension acting at the thread end, ƒ0, ƒ1; normal force acting at the thread end, θ0, θ1; contact angle to the standard line, α0, α1; angle between thread at its end and perpendicular to the standard line.3). When the thread is long enough (Fig. 5)Using the relationships between the angles and equation (b) following formulas are obtained: The relationships between t0 and t1 are;where, E; Young's modulus of the thread, I; moment of inertia of area of the thread, i.e. EI shows the flexual rigidity of thread, ρ; radius of cylinder.the relationship between θ0 and θ1 is:But, where the point contact or θ0+θ1=0, and4). It has been found on the constant coefficient to friction as following:i) The frictional force with rigidity is smaller on the thread than without (Fig. 8 and Fig. 9).ii) The frictional behaviour may be approached to condition without rigidity as thread tension becomes greater (Fig. 8 and Fig. 9).iii) The greater the coefficient of friction and turning angle are the more the frictions are influenced by flexual rigidity. And as these values are smaller these influences are trivial (Fig. 10).iv) When the contact is at point, the ratio of final tension to initial tension is not changed by the tension of the thread as shown in equation (e).v) When the contact is at point, its position does not change with the thread tension, as shown in equation (f.)5). In general threads similar tendencies may be expected (Fig. 11).

Measuring the profile angle of internal conical threads

Measuring the profile angle of internal conical threads

Device for measuring the thread angle of screw thread plug gages

Device for measuring the thread angle of screw thread plug gages

めねじの測定

It is very difficult to measure the thread pitch and angle in the nut. In this report, the plastic material such as Cu amalgam and dental wax is casted in the nut to obtain a casting for the nut. Its pitch and angle are easily measured, because the casting has external thread. The coefficient of thermal expansion of the dental wax is measured and the aging effect of Cu. amalgam is researched in order to research the source of the error for this measurement. As the result, Cu amalgam is preferable to the dental wax for the measurement of the nut.

On the One Axis Screw Pump

The authors gave a design formula of the axis screw pump using optimum depth and helical angle of the screw thread under the laminar theory. Experimental studies were made upon four screws.

Thread Forms of Milled Worms: Progress Report No. 3 of the A.S.M.E. Special Research Committee on Worm Gears

Abstract This paper is a continuation of the material on helicoidal sections given in the author’s paper on “Worm-Wheel Contact” presented before the Society in December, 1926. It covers the equations necessary to determine the thread form of milled and ground threads in various sections and also the sections of a helicoid formed by a straight-sided lathe tool, set toward the helix angle of a thread. This last helicoid is a convolute helicoid with the inclination of its generatrix in the opposite direction to that of the helix. As an example, the worm used in the drive AW-3 in Progress Report No. 2 of the A.S.M.E. Special Research Committee on Worm Gears has been analyzed and the coordinates of the thread form in an axial section have been determined when the thread is produced by a lathe tool, a 4-in.-diameter thread milling cutter, a 12-in.-diameter grinding wheel, and by the flat side of a grinding wheel which would produce an involute helicoid. This analysis shows that the form in the axial section of a thread produced by a lathe tool, tipped toward the helix angle, will be concave. That produced by a milling cutter may be concave, convex, or a form of double curvature, depending upon the diameter of the cutter, angle of thread, diameter and lead of screw, and depth of thread. The curvature increases with a reduction in thread angle and an increase in helix angle. The milled forms become more convex with an increase in the diameter of the cutter or grinding wheel. This paper is another attempt to introduce more mathematics in the machine shop to the end that we may know more definitely the conditions with which we are contending.