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HARTNESs SCREW THREAD COMPARATOR
mechanism using threaded parts, and at the same time
it is a means of speeding up production and reducing
the cost of good threads.
The visual method measures screws and taps on
the basis of actual values in fits and not on the "go"
and "no go" gages that may reject the best and accept
the worst.
This new basis of measurement is essential to the
most satisfactory performance of machinery.
It is the easiest way to good dependable screw
thread fits.
A dependable screw fastening is one that has a
known depth of engagement of threads of the mating
parts and a fairly uniform distribution of stress over
many threads. In other words, it has a good area of
surface in contact between the mating parts which
stand the stress of the work.
While it is true that we may depend on the flow
of the metal to make mating parts fit, provided one
part is of soft metal, and that the stress of wrench,
or the working stress may squeeze the mating thread
into a fair fit, the fact remains that even with soft
metals the most reliable fastening is one in which the
threads have been well formed by the machine process
before being subjected to the stress of work. By the
visual method of gaging we can eliminate those screws
that have errors of a kind that cannot be corrected by
the metal flow.
In order to get the most dependable fastening or
means of adjustment the threads must have well
formed flanks of reasonable pitch diameter and fairly
good lead. These elements are instantly seen by the
visual method and are generally not discovered by the
"feel" system.
The End Thread Visual Method assorts screws
and taps on a reliable performance standard and not
15
Document source description
This is a publication about a comparator machine for the inspection of screw threads, with illustrations by Russell W. Porter.
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"ocrText": "HARTNESs SCREW THREAD COMPARATOR\nmechanism using threaded parts, and at the same time\nit is a means of speeding up production and reducing\nthe cost of good threads.\nThe visual method measures screws and taps on\nthe basis of actual values in fits and not on the \"go\"\nand \"no go\" gages that may reject the best and accept\nthe worst.\nThis new basis of measurement is essential to the\nmost satisfactory performance of machinery.\nIt is the easiest way to good dependable screw\nthread fits.\nA dependable screw fastening is one that has a\nknown depth of engagement of threads of the mating\nparts and a fairly uniform distribution of stress over\nmany threads. In other words, it has a good area of\nsurface in contact between the mating parts which\nstand the stress of the work.\nWhile it is true that we may depend on the flow\nof the metal to make mating parts fit, provided one\npart is of soft metal, and that the stress of wrench,\nor the working stress may squeeze the mating thread\ninto a fair fit, the fact remains that even with soft\nmetals the most reliable fastening is one in which the\nthreads have been well formed by the machine process\nbefore being subjected to the stress of work. By the\nvisual method of gaging we can eliminate those screws\nthat have errors of a kind that cannot be corrected by\nthe metal flow.\nIn order to get the most dependable fastening or\nmeans of adjustment the threads must have well\nformed flanks of reasonable pitch diameter and fairly\ngood lead. These elements are instantly seen by the\nvisual method and are generally not discovered by the\n\"feel\" system.\nThe End Thread Visual Method assorts screws\nand taps on a reliable performance standard and not\n15"
}