markings on Screw Pitch Gauge?

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 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?

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

"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

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?

"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.

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