Anyone an expert on using Thread Parallels?
Presumably they need a table of sizes, or at least a constant
thickness to add to get the target size. Is it just a case of putting
the root one and the crest one togther, measuring their thickness and
adding it to the target size you are shooting for ?
No John I mean Thread Parallels - made by several companys but mine
are made by Marlco. The consist of pairs of ground profiles covering a
range of pitches and available in 47.5, 55, and 60 degrees. A pair
consist of what looks like a slip guage with thread profiles
projecting, and a plastic clip to hold them on the thread with the
thread being the meat in a sadwich, and the parallels being the bread.
One has a single protrusion to go in the thread valley, and the other
has a pair to go ober a crest.
Funny thing is John, that by looking for that reference for you I have
answered my own question! if you read the text below the picture it
confirms that you bung the pair together, zero your mic on them, then
slap them either side to the thread and measure the effective
ps not flogged all those thread wires yet?
How do you zero a 0-1" M&W micrometer ? Mole grips ?
Loads of thread wires left, bought a box of 500, how many do you want
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"John Stevenson" wrote in message >
Well I just press the button for relative measurement and the
electrickery sorts it out for me, but if you cannot easily set an
offset zero on your gas powered set then measure, get an offset value
and deduct it from the next over thread measurement - but I guess you
probably knew that
Trouble is that threads, unlike gears, are not specified by 'effective
diameter'. This means that, unless the parallels come with a table of
measurements, one must calibrate the reading by using a thread standard
(GO-NOGO gauge or bolt depending on what's available :).
Sorry to disagree, but threads are exactly specified by their effective
It's the reason we always used wires to check tied up threads rather
than any ring gauges. The devices the OT mentioned were for Male
threads, so a plug gauge or bolt isn't going to work ;)
Plug gauges are tested with wires, I've seen it done in a UKAS
It seems to me the thread parallels mentioned are a pretty good idea,
looks certainly much easier than thread wires. Not a cheap solution though!
On or around Mon, 06 Nov 2006 00:03:19 GMT, Wayne Weedon
enlightened us thusly:
only if you know what thread it is; I daresay that there are at least some
cases where the thread forms differ but the ED is the same. I've got a big
list somewhere of nearly every kind of thread, arranged by size.
had an amusing example recently - a friend acquired some cheap BMX bike
wheels for a project. He asked the shop-droid what size the axles were and
was told 10mm.
The wheelnuts are the kind with a tapered flange on and have 15mm AF hex,
the locknuts are 17mm hex.
The axle, and its thread, are 3/8" BS Cycle. M10x1 nuts will actually go
onto this but imperfectly, whereas the nuts supplied won't go on a 10x1
Well it's useful to have lots of thread data around. Even a Zeus book
has a fair bit of data including effective diameters. It's only the
Pitch thats important at the end of the day. It's easy to calculate
effective dia for threads having same pitch but different diameters,
when you have data for at least one.
Modern Cycle threads are a real mix.
Different interpretation of the words what I wrote.
To elucidate, possibly I should have said "Threads are not bought by effective
diameter at the nut and bolt shop. They are bought by nominal outside
diameter". Gears, on the other hand are almost always specified in the gear
shop either by diametral pitch, or by module (which is pi/diametral pitch).
Diametral pitch is a very real and integral part of gear usage. Whereas on
threads effective diameter is a fairly arbitrary function, e.g. on the
Hardinge cross and topslide screws I'm working with at the moment... square
section thread=undefined effective diameter!
To expand my comment further, In the absence of a table of effective diameters
for a particular thread, holding the thread parallels together and zeroing the
micrometer against them will not help to identify, or measure a thread.
Holding the parallels around the correct plug gauge and zeroing about that
will give a usable calibration for male threads of that form. This is not
using the gauge to test the threads, it's using the gauge to represent the
But you still need to check the major diameter for male and minor diameter for
female threads if you've got fitting problems, unless you use a projector to
verify the thread form that was cut (as opposed to the one that was called
for), which is a pain for female threads. DAMHIKT!
Agreed that thread parallels are far superior to thread wires.
I've forgotten what Andrew's original post was about now. Damn
The original post was Andrews concern whether kippers caught in the
Irish sea had Irish standard threads or Manx threads.
Irish threads are full form whereas Manx threads are truncated and you
need three hands to tighten them.
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Who's confused now LOL...
It's not arbitrary when you're trying to please a pedantic chief
inspector ;) Fortunately I work for myself these days, and those blokes
are just a distant memory. Still use thread wires on occasion though,
especially when the thread is to be plated.
As I mentioned earlier, you only need the data for a particular pitch,
the rest can be calculated.
You can get unstuck there! If the major or minor diameters are
correct, the effective can still be way off the mark! Who's being
Especially when you drop one in piles of swarf!
Hehe... It's all in the subject line! " Using Thread Parallels" This
is probably where the confusion lies, this thread about thread parallels
was about how to use them not identifying threads ;)
And of equal relevance, did you know that the volume of a pizza of
thickness 'a' and radius 'z' is given by pi*z*z*a? Not sure whether
the presence or absence of kippers on the pizza has any effect on this