markings on Screw Pitch Gauge?

[Alan Horowitz]

I've got an old screw pitch gauge that I inherited. There's no mfr's
name marked on it, just "Number 137".

the individual leaves are marked with two numbers each, but these
numbers are not reciprocals. The first number is always a small
integer which I presume is threads-per-inch.

the second number is always a decimal.

All the leaves are of equal thickness, so they are not thickness
calibrations as in a feeler gauge.

Any idea what the second set of numbers are?

[Don A. Gilmore]

Probably metric (in millimeters pitch)

Don

"Alan Horowitz" > wrote in message
om...
> I've got an old screw pitch gauge that I inherited. There's no mfr's
> name marked on it, just "Number 137".
>
> the individual leaves are marked with two numbers each, but these
> numbers are not reciprocals. The first number is always a small
> integer which I presume is threads-per-inch.
>
> the second number is always a decimal.
>
> All the leaves are of equal thickness, so they are not thickness
> calibrations as in a feeler gauge.
>
> Any idea what the second set of numbers are?

[Ned Simmons]

In article <1e3670a7.0402091459.5206f388
@posting.google.com>, says...
> I've got an old screw pitch gauge that I inherited. There's no mfr's
> name marked on it, just "Number 137".
>
> the individual leaves are marked with two numbers each, but these
> numbers are not reciprocals. The first number is always a small
> integer which I presume is threads-per-inch.
>
> the second number is always a decimal.
>
> All the leaves are of equal thickness, so they are not thickness
> calibrations as in a feeler gauge.
>
> Any idea what the second set of numbers are?
>

Probably the depth of the thread--handy to know if you're
cutting threads on a lathe. If you post a few examples it
would be easy to verify this.

Ned Simmons

[Harold & Susan Vordos]

"John Manders" > wrote in message
...
>
> "Alan Horowitz" > wrote in message
> om...
> > I've got an old screw pitch gauge that I inherited. There's no mfr's
> > name marked on it, just "Number 137".
> >
> > the individual leaves are marked with two numbers each, but these
> > numbers are not reciprocals. The first number is always a small
> > integer which I presume is threads-per-inch.
> >
> > the second number is always a decimal.
> >
> > All the leaves are of equal thickness, so they are not thickness
> > calibrations as in a feeler gauge.
> >
> > Any idea what the second set of numbers are?
>
> Depends upon whether it's metric or imperial.
> The most likely is that the first is TPI, as you say. The second is
probably
> the bolt diameter in a thread series. The most likely is BSW.
>
> John

The second set of numbers, decimals, is the double depth of the thread pitch
..

Harold

[Jim Pugh]

Alan, while awaiting the answer from those more knowledgeable, see if you
can borrow a Machinery's Handbook. Most machinists and mechanical
draftsmen will have a copy. It will explain more than you want to know
about threads. And, the American Standards Association (ASA) sets the
standard on screw threads and a whole bunch of other things as well.

Alan Horowitz wrote:

> > I've got an old screw pitch gauge that I inherited. There's no mfr's
> > name marked on it, just "Number 137".
>
> > the individual leaves are marked with two numbers each, but these
> > numbers are not reciprocals. The first number is always a small
> > integer which I presume is threads-per-inch.
>
> > the second number is always a decimal.
>
> > Any idea what the second set of numbers are?
>
> pairs of numbers are
> ~~~~~~~~~~~~~~~~~~~~
> 60 - 0.021
> 48 - 0.026
> 40 - 0.032
> 32 - 0.040
> 30 - 0.043
> 28 - 0.046
> 26 - 0.049
> 25 - 0.051
> 24 - 0.063
> 22 - 0.058
> 20 - 0.064
> 19 - 0.067
> 16 - 0.080
> 14 - 0.091
> 13 - 0.098
> 12 - 0.107
> 11 - 0.115
> 10 - 0.126
> 9 - 0.142
> 8 - 0.160
> 7 - 0.183
> 6 - 0.215
> 5 - 0.259
> 4-1/2 - 0.284 (sic)
> 4 - 0.320
>
> looking at the leaves, "depth of thread" in inches seems the most
> plausible to me. This item would date back to the 50's, I don't
> believe there was too much metric action in American machine shops at
> that time.
>
> I'd try _measuring_ the depths with a micrometer, but I don't know
> where to measure to/from. How is thread depth defined? And by the
> way, who sets the standards on how these things are measured?

[Jonathan Barnes]

"Jim Pugh" > wrote in message
...
> Alan, while awaiting the answer from those more knowledgeable, see if you
> can borrow a Machinery's Handbook. Most machinists and mechanical
> draftsmen will have a copy. It will explain more than you want to know
> about threads. And, the American Standards Association (ASA) sets the
> standard on screw threads and a whole bunch of other things as well.
>
> Alan Horowitz wrote:
>
> > > I've got an old screw pitch gauge that I inherited. There's no mfr's
> > > name marked on it, just "Number 137".
> >
> > > the individual leaves are marked with two numbers each, but these
> > > numbers are not reciprocals. The first number is always a small
> > > integer which I presume is threads-per-inch.
> >
> > > the second number is always a decimal.
> >
> > > Any idea what the second set of numbers are?
> >
> > pairs of numbers are
> > ~~~~~~~~~~~~~~~~~~~~
treat the first number as TPI
I have added witworth form thread depth in inches.....
doubleing it gives the second number.

> > 60 - 0.021 0.0160009
> > 48 - 0.026 0.013340
> > 40 - 0.032 0.016008
> > 32 - 0.040 0.020010
> > 30 - 0.043
> > 28 - 0.046 0.022869
> > 26 - 0.049 0.024628
> > 25 - 0.05
> > 24 - 0.063 0.026681
> > 22 - 0.058 0.029106
> > 20 - 0.064 0.032016
> > 19 - 0.067 0.033702
> > 16 - 0.080 0.040020
> > 14 - 0.091 0.045738
> > 13 - 0.098
> > 12 - 0.107 0.053360
> > 11 - 0.115 0.058212
> > 10 - 0.126 0.064033
> > 9 - 0.142 0.071147
> > 8 - 0.160 0.080041
> > 7 - 0.183 0.091475
> > 6 - 0.215 0.106721
> > 5 - 0.259 0.128065
> > 4-1/2 - 0.284 (sic) [ 4.5 ] 0.142295
> > 4 - 0.320 0.160082

N.B. unified thread depth is diferent, at 40 tpi for exampe it's 0.015336.

Hope this helps
> >
> > looking at the leaves, "depth of thread" in inches seems the most
> > plausible to me. This item would date back to the 50's, I don't
> > believe there was too much metric action in American machine shops at
> > that time.
> >
> > I'd try _measuring_ the depths with a micrometer, but I don't know
> > where to measure to/from. How is thread depth defined? And by the
> > way, who sets the standards on how these things are measured?
>

--
Jonathan

Barnes's theorem; for every foolproof device
there is a fool greater than the proof.

To reply remove AT