Thread measuring

Greetings All,

We use the Marlco thread measuring parallels,
which work well and can create very accurate
threads anywhere in the tol range.

I also have 30 students who would like their own
but at the price it is not going to happen.

some years ago, I downloaded a Machinists calculator. There is a program that calculates
ideal wire thickness or a wire thickness you actually have.

So, I got thinking, as we only use about 10
common metric pitches, could one make the calcs
and use HSS drill blanks and join them up with
thin plastic tube ( empty ballpoint refills)
and make a set of 3 each. One could also make
a master to the correct spec and transfer it to
a chart. Once done, and a part get's lost, one
just buys another drill blank.

What about piano wire. I think that would be cheap, but how accurate is it. A drill blank
I can get with a phone call. I also have never
seen anything like this for sale, but am sure
the're out there. Mics ore out of the question
as it must fit an appie's pocket.

What do you think guys?
Andy

You really like making life difficult with that idea dont you...

Drill Blanks do not come in the proper size.
Piano wire is soft and who knows what size

Thread Measuring Wire sets are so well made for EXACTLY THIS JOB and packaged well and come with it's own chart and formulas, you'd have to be a fool to not use it.

AC --

Here in the States we have "Pee Dee Wires" (I'm pretty sure that's a tradename.) that do just what you're asking about. Take a look at them here: http://www.cartertools.com/fmpdtg.html

Finding Pee Dee Wires in your part of the world might be a challenge, but a now-retired coworker here had a British-made set of wires that was conceptually identical if slightly different in execution (wire sizes slightly different, with tables to suit), so I wouldn't think the idea would be unknown in SA.

Have your tool dealer take a look at Nick Carter's website (linked above), it'll go a long way toward helping him understand what you're looking for.

John

ive used wires and thread mics but the hot ticket for me now is thread triangles.

only 2 moving parts.

three different flats to cover a wide range of thread pitches.

and best of all they are attached to some plastic spaghettti so you can see them if you drop them...jim

The drill blanks are HSSco. They are accuratly
ground. Once you know what you get and make a chart, whats wrong with that?

I often check threads with a vernier, once a master is measured you have a comparitor. I have
worked inside to outside, inside to inside and
never had a problem. Ok it is for rough checks
but it works.

I also fitted a m/female blade to a vernier jaws
and still use it. I made them for 1 pitch only
and exactly 6mm over the effective dia. Works
perfect. I used a 60 deg side and face cutter
and a slitting saw to allow for the burr on top of the thread in the v. It was constrcted as not
to touch the outer threads and the other side had a flat on the point of the v the same as Marlco. It works perfect. I used a 300mm vernier.
That is now dedicated for 3mm pitch for a regular
job. I used ground stock and toughened it.

Andy

If you are teaching students i think it is important to school them on a system that they might encounter no matter where they might go and work...sort of teaching them a universal language instead of a dialect that is only understood in one village on the plannet....Thread measuring wires such as the Pee-Dee sets are relatively inexpensieve..they are guaranteed for life even if you loose a wire they will replace them...and they are understood by every machinist on the plannet....seems like the only rational choice to me.
Cheers Ross

check out sewing needles, we used them on an engineering inspection course to check effective diameter of thread, they are remarkably consistant, there is a formula for wire diameter which gives the ideal theoretical dia, but there is a formula for under/over diameter pin will find them for you, ther is also a table of needle sizes, but these are British Standard needles.
mark

I have never heard of PEE DEE wires in my life.
That set looks affordable, a bit long though.

I ran the excersize with the wires (drill blanks), I drilled the ends of cable ties
to hold 2 on on side and one on the other.

They were repeatable within about 4 micron.

One must appreciate we live in Africa and lack
resources for nice stuff, I can only gloat when
I see pics of your gun shops, not to mention tackle,
Anyway, our industry is fighting a battle to keep standards up and not fold under pressure
from incompetants. I like to give my kids
workable solutions for problems whether they
ever need them or not. The thead measuring triangles sound like the Marlco set we use
at our training centre. We only use the best we can afford or get our hands on as a benchmark
for standards, I just come from an old school
and a old teacher and was pushed with what ifs
and the usual snide Think! you hav'nt got the tool, make a plan! I think it seved me well.

Thanks for the input
Andy

AC --

A couple of decades ago I took an evening trade-school machining class that was taught by a gentleman who spent his days being a Reliability Engineer at IBM's hard-disc manufacturing plant in San Jose, California. One of his exercises involved single-pointing a pair of different external screwthreads on one shaft . . . and we students were required to make two sets of thread wires, in appropriate sizes, before starting to machine the shaft.

Each student was issued a six inch length of copper-plated gas welding rod as thread-wire stock. We were expected to chuck the rod short and face it before rechucking with about 7/8 inch sticking out of the jaws, crank the lathe up to its highest speed (which varied quite a bit from lathe to lathe), and turn the rod to our target diameter using a honed HSS toolbit, and then cut it off.

The diameters of all three wires for a given Pitch were to be within 0.0002 inch maximum-to-minimum spread and between the handbook's maximum and minimum wire size for that Pitch.

Once we'd completed the exercise, including calculating the maximum and minimum over-wires measurements for the actual size wires we'd made and showing that our over-wires measurement of the thread we'd cut was within the tolerance zone, we were then required to remeasure using the Pee Dee wires and compare the results.

I would commend his exercise to anyone learning to single-point screwthreads, but in the situation you describe, I can only strengthen that commendation.

John

the length of peedee wires is so you can do a wide range of sizes and have somewhere to hold the wires. in many case you can balance 2 wires on top of the shaft in the chuck... hold the third and run the mike without running out of fingers. the wire tie trick and/ or soft foam to hold the wires as a 4th hand are easier for smaller threads.

Thread Triangles! Are there any name brand ones? I have tried four sets, not one the same. Thanks Cliff

I have a set of wires like those but they are not
called PD's. They are a little clumsy sometimes bordering a PIA but they work, English and Metric.
Old Bill

I'm wondering if measuring the major diameter of the threads and using a point micrometer to measure the minor diameter would not be a good way to measure threads? You reference a thread spec chart and look up the measurements. I seldom need to verify a thread so I have not made the investment in an expensive thread micrometer. As for using the wires that is a good option but I really only have one hand that can work with small items like the wires. Besides using the wires you still need to do calculations. It seems to me the point micrometer and the thread chart have some advantages.

These thread triangles come with neoprene parts to help keep them in the mikes

http://67.59.156.7/merchant2/merchant.mvc?Screen=PROD&Product_Code=16704

I think your idea is excellent. It may not be the tools used in the industry, but as a retired math and physics instructor, I know it would force the students to think and understand the the processes and the as importantly the MATH involved. I can think of no better way of teaching students. Make them think by developing their own tables. A drill blank may not be the industry standard but there is no reason why it can not be your standard. All industry standards where established based on some kind of logic at some point in time. I commend you for your teaching methods

As for using the wires that is a good option but I really only have one hand that can work with small items like the wires. Besides using the wires you still need to do calculations.

Click to expand...

Only one hand?...
A small amount of Vaseline Petroleum Jelly holds the wires in place while you measure.

Calculations??
Can you add and subtract?

There's really no excuse for not using them other than it does take a little longer than using either the Triangles or a Thread Mic.. and if you measure a lot of threads, buy a mic.

Appie Chappie: I would like to relate a personal experience, that would reinforce your idea.

The shop where I learned my trade had several different methods of measuring external threads, Thread pitch mics, Thread Ring gauges for the more common sizes, and precision wire sets when necessary. We would frequently have to "chase", single point, standard acme, stub acme, and butress threads.

Fast foward a few years , a new job and a different shop, while working 2nd shift, there was a breakdown in the plant,and I was the lucky reciepient of that breakdown, It involved chasing a acme thread, I can't remember the sizes now, but Normally they would have thread ring gauges for all the threaded parts comming thru the shop, but there was none to be found. And to my suprise no Thread Wires at all. They did have thread triangles. (useless for acme threads). So I did the next best thing and it's pretty much what you are proposing to do. I found the best wire size for the thread in question , then checking my number drill chart I found a drill size that was within a few ten thousands of the wire size necessary (I actually used the shank of the drill) Then using the formula required I plugged in the drill size and obtained the Measurement over wires for that specific thread. I might add this acme thread had a tighter tolerences than your standard acme used for transmitting motion. The application here was for a closure on a pressure vessel, so you couldn't just measure flats or depth of thread as you might on some loose fitting acme threads.

Standard thread wires are the way to go, when you have them , But sometime you have to think outside the box. Your students will lose nothing by applying your Idea, but will gain valuable insight into improvising when necessary.

Gary E
The set comes with constants for each pitch,so all
you do is add it to pitch dia.
Old Bill

I want to thank Gary E for his excellent suggestions. But if you read my prior comment it was a question on using a point micrometer. I was asking this group if a point micrometer to measure the minor diameter and measuring the major diameter would not result in identifying a particular thread.
As for knowledge of vaseline and its uses I think I've explored those quite well in the last 73 years. If you really use wires I think you can agree that the calculations are a bit more than 2+2. Measuring as I suggest may be an alternative which only requires consulting a thread spec chart. DUH!
Of course an intelligent machinist probably has a good supply of nuts and bolts or thread gauges to do his thread measuring. If not Travers Tools has a nice set of everything you could ever want for $24.