Using Thread Parallels

You mean thread wires ? -- Regards,
John Stevenson Nottingham, England.
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putting 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.
See for an example
AWEM

thickness covering a 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 diameter.
AWEM
ps not flogged all those thread wires yet?

Sorry can't help, got a table for thread wires but not these. -- Regards,
John Stevenson Nottingham, England.
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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 ???? -- Regards,
John Stevenson Nottingham, England.
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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
AWEM

J&S 540 grinder :-)
Mark Rand RTFM

Andrew
Sometimes the obvious is difficult to see, look on the Marlco Websit of course.
I bet it is an M10 thread you are trying to measure.
Regards Phi
-- pgp00 ----------------------------------------------------------------------- pgp001's Profile: this thread:

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 :).
Mark Rand RTFM

Website Close but no cigar - it's 3/4 BSP !
Andrew

They used to come with a c spanner.

Sorry to disagree, but threads are exactly specified by their effective diameter.
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 calibration lab.
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!
Wayne....

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 axle.

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.
Wayne...

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 threads.
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
Regards Mark Rand
Mark Rand RTFM

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.
. -- Regards,
John Stevenson Nottingham, England.
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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 pedantic now!
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 ;)
Wayne....

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 result...
Regards, Tony