THREAD MEASURING TOOL

Abstract: When using a thread measuring tool with a "go" plug gauge (1) and a "no go" plug gauge (4) and scale (13) indicating the thread depth, the gauge is worn or damaged so that the tool must be discarded. By providing the tool with interchangeable gauges (1, 4), as referred to in the application, it is possible to replace the worn or damaged gauge in that the gauge is placed on a shank (2, 5) which can be inserted into a tapered bore (3, 6) in a rod (7). The rod extends inside the housing (16) of the tool. When for instance a plug gauge (1) is worn down, it is extracted from the rod (7) and a new one is inserted. In order to be able to adjust the tool, the rod (7) is provided with an external thread (17) so that it can be screwed in and out of the housing (16) and thus be adjusted so that the end of the plug gauge holder (12) will just flush with the end of the plug gauge (1).

Description: THREAD MEASURING TOOL The invention relates to a thread measuring tool with a "go" plug gauge and a "no go" plug gauge, said gauges being arranged in a housing, and where a plug gauge holder with a measuring value indicator is arranged around the plug gauge, which holder can be inserted telescopically into the housing against a spring. Thread measuring tools of this type can be used for checking the tolerances of the thread holes while the thread depth can be read direct from a measuring value indicator. By the hitherto known tools the "go" plug gauge and the "no go" plug gauge are designed at each end of a through-going spindle extending through the housing. In use these plug gauges can be damaged and they are worn. When one or both plug gauges do no longer meet the requirements in respect of tolerance, shape etc., the whole tool must be discarded or at best be pro¬ vided with a new spindle with plug gauge. The replacement of the spindle with plug gauges can normally only take place while at the same time adjusting the measuring value indicator of the tool, because the plug gauge must be flush with the end of the plug gauge holder in order to provide an accurate reading of the thread depth. Therefore, the tool will normally be discarded when the plug gauges do no longer meet the tolerance re¬ quirements, which is a source of considerable dis¬ advantages and expenses for the consumer. Add to this that a measuring tool for each thread type and thread size must be used. This requires a considerable number of measuring tools which is expensive for the consumer who may only occasionally require thread check. It is the object of the invention to overcome these shortcomings of the known measuring tools, and this is achieved by a tool where the gauges are each situated on a shank which can be attached to a rod extending inside the housing. Considerable advantages in use and by way of reduced costs are hereby obtained. First of all the replace- ment of a worn down or damaged gauge is simple and comparatively inexpensive. It will thus suffice to replace only one gauge thereby saving money for the replacement of the other gauge. Add to this that other sizes of plug gauges can be placed in the same tool whereby both the field of tolerance as well as thread types and sizes can be varied within a wide framework within the one and same tool. This provides large practical advantages and reduces the costs con¬ siderably. By, as presented in claims 2 and 3, being able to attach the shank of the gauges in a bore, a reliable and accurate mounting of the gauge is obtained by a slight conicity. By, as presented in claim 4, being able to adjust the position of the spindle in the housing, the measuring value indicator of the tool can be adjusted exactly to the plug gauge. Finally, it is expedient, as presented in claim 5, to adjust by screwing the rod into the housing. In the following the invention will be described in further detail with reference to the drawing, where Fig. 1 shows the individual parts of the tool, Fig. 2 shows the assembled tool, and Fig. 3 is a section through the tool on a larger scale. The drawing shows an example of a preferred embodi- ment of the thread measuring tool. The individual parts, cf. particularly fig. 1, com¬ prise a through-going spindle 7 being provided with a bore 3, 6, said bores being somewhat pointed towards the bottom for the formation of a tapered guide for the shanks 2, 5 of the plug gauges. The plug gauge 1 is provided with a cylindrical shank 2, and similarly the "no go" plug gauge 4 is provided with a cylindrical shank 5. By pressing the shank 2, 5 into the tapered bore 3, 6 the gauge is held fixed¬ ly and accurately in the spindle 7. Moreover, the spindle 7 is at one end provided with an external thread 17 which can be screwed into an interacting inside thread in a thread bushing 10 forming the one end of the housing. By means of this thread 17, the spindle 7 can be adjusted in relation to the housing in that the spindle can be screwed in and out. In order to be able to lock the spindle 7 in the housing, a stop screw 9 is screwed into the thread bushing 10, which stop screw 9 can be screwed down to abut the spindle 7 in a shoulder 8. The remaining part of the housing comprises a tube 16 into which the thread bushing 10 can be screwed. In the opposite end of the housing 16 this is somewhat pointed and is moreover cut off straight. This is in order to read the depth accurately, said depth being read from a measuring indicator 13 placed on the out¬ side of the plug gauge holder 12. This is constructed as a tube with a sliding guide member 15 at the inner end, which guide member can slide inside the housing 16, cf. fig. 3. Inside, the gauge holder 12 is provided with a recess 14, on which a coil spring 11 can abut. The opposite end of the spring abuts the end flange of the thread bushing 10 in the housing. The spring 11 presses the gauge holder 12 outwards so that it can slide out and cover the plug gauge 1, as shown in fig. 2. The entire measuring tool can be assembled in the manner shown in fig. 1. Once the tool is assembled, it appears as shown in fig. 2. The plug gauge 1 is hidden by the gauge holder 12, and the tool is ready for use. In fig. 3 the tool is shown in use in that it is screwed down into a thread hole being indicated by the dotted line. It is seen that the gauge holder 12 is inserted into the housing, and the length, and hence the depth, of the thread can be read from the measuring indicator 13 against the end edge of the housing 16. The two plug gauges 1, 4 can be removed and replaced by others, if so required. The tool can perhaps be adjusted if the plug gauge 1 is no longer flush with the end of the plug gauge holder 12. This takes place by releasing the stop screw 9 and turning the gauge 1 and spindle 7 until the gauge is flush with the end of the gauge holder. The tool is then adjusted and will provide an exact indication of the thread depth.

Claims: P A T E N T C L A I M S 1. Thread measuring tool with a "go" plug gauge and a "no go" plug gauge, said gauges being arranged in a housing, and where a plug gauge holder with a mea¬ suring value indicator is arranged around the plug gauge, which holder can be inserted telescopically into the housing against a spring, c h a r a c ¬ t e r i z e d in that the gauges (1, 4) are each situated on a shank (2, 5) which can be attached to a rod (7) extending inside the housing (10, 16). 2. Thread measuring tool according to claim 1, c h a r a c t e r i z e d in that the shank (2, 5) is inserted into a bore (3, 6) in the spindle (7). 3. Thread measuring tool according to claim 2, c h a r a c t er i z e d in that the shank (2, 5) and the bore (3, 6) are cylindrical and tapered, respectively, or vice versa. 4. Thread measuring tool according to claim 1, c h a r a c t e r i z e d in that the position of the spindle (7) in the housing (10, 16) can be adjusted so that the distance of the gauge (1) from the housing (16) can be adjusted. 5. Thread measuring tool according to claim 4, c h a r a c t e r i z e d in that the spindle (7) externally and the housing (10) internally are pro¬ vided with an interacting thread (17).

Inventors: LARSEN LEIF GRUNDTVORM, LARSEN, LEIF, GRUNDTVORM
Applicants: LARSEN LEIF GRUNDTVORN, LARSEN, LEIF, GRUNDTVORM
Application year: 1987
Main classification: G01B3
IPC codes: G01B3