Thread Triangles Vs. Thread Wires Vs. Thread Mics?

[BGHansen]

Curious as to what the advantages/disadvantages are between each of these methods for checking threads. I've got a set of wires, only used them once. Used a couple of O-rings on the ends to hold them to the work when checking, but still seemed to be a cumbersome method.

I like the simple concept of the triangles, but it looks like you're checking across the helix, not the true root diameter. Plus, the sharp edged triangles don't necessarily bottom out at the root of the threads. There are probably charts out there for your target dimension or maybe the simplest way is to measure a known good thread and cut to match? Advantage is, like the wires, they are good for a wide range of threads and diameters.

Or do I bite the bullet and pick up a set of thread mics (Shars 0-1" are under $60, 1"-2" around $70)? I don't do a tremendous amount of single point threading but don't mind spending the money. My shop will eventually go to my son.

Or, my normal "go to" method of making a few thousandths pass and checking with the mating part? It's a little cumbersome having to slide the tail stock away from the end of the work but it naturally works well assuming I have the mating part completed and it can be brought to the lathe instead of the work being removed from the chuck and checked on the mating part.

Just curious which method the more experienced guys use. I realize there probably isn't a best method for all occasions, looking for something I may have missed (strongly leaning toward picking up the mics).

Thanks for the guidance, Bruce

Triangles

Wires

Mic

 

[bill stupak]

Hi Bruce, check this video for using the 3 wire method.

Bill

 

[mmcmdl]

Nothing wrong with the wires . They work on any diameter threads and not limited as mics are . You get used to them over time after dropping them into your chip pan . But if ya like to spend money ......

 

[TommyD]

I guess it all depends on what accuracy you are looking for. Iworked at an aircraft job shop that did a ton of aircraft threading on thread rollers, mostly J threads and a lot of them had to be plated with various coatings a few angstroms thick. We used Tri Rolls to check the threads. If I remember correctly, it is the pitch diameter that is critical since the major diameter can be truncated and threads should never bottom on the minor diameter. To me, either would be acceptable or you could use an optical comparator.

 

[T Bredehoft]

There are a couple of considerations, Re: wires, triangles and mikes. I think no. 1 is cost. considering that you need a small number of mikes for each size ( one, two, three Inch or metric) makes a series of thread mikes too cost expensive for the average hobbyist. Triangles are easier to use than wires, but IMHO not as accurate. When I worked for a living, I had one of each (up to three) size of thread mikes and regretted not having a whole set. I still have the three mikes, and the one thread I chased recently was not the right pitch for the mike I had. So I used the wires.
The use of a cork, or some such to hold the wires is a great improvement over trying to hold them by hand.

 

[mmcmdl]

The use of a cork, or some such to hold the wires is a great improvement over trying to hold them by hand.

Piece of Styrofoam works great also . I can't tell you the amount of times I crawled around in chip pans looking for a lost wire .

 

[RIMSPOKE]

I RAN A CNC LATHE WHERE WE CHURNED OUT VALVE STEMS FOR EDWARD VALVES .

THESE GO IN NUCLEAR POWER PLANTS , CAME IN ALL SIZES AND HAD ACME THREADS .
IN FACT , THEY WOULD THROW EVERY CURVEBALL IMAGINEABLE AT YOU .

THEY USED THEIR OWN THREAD SYSTEM , ( EDWARDS ACME ) LEFT HAND THREADS ,
ODDBALL PITCHES AND DIFFICULT TO CUT EDWARDS SUPPLIED MATERIALS .

EDWARDS SUPPLIED THE GO-NO GO GAUGES FOR SOME OF THEM BUT IF WE WERE RUNNING
ONE WITH OUT THEIR SUPPLIED INSPECTION TOOLS , THE THREE WIRE METHOD WAS ALL THAT WE HAD .

I GOT PRETTY GOOD AT IT . I FOUND IT TO BE PRETTY EASY ONCE YOU GET USED TO IT .
I WOULD 100% INSPECT THE PARTS BEFORE THEY CAME OFF THE LATHE .

INSERT WEAR ON SOME OF THOSE MATERIALS WAS CRAZY & THE PARTS WERE CRITICAL .

 

[4GSR]

With all of the special threads I've designed and others that I didn't design, I always used thread wires to measure external thread P.D. with. For internal threads we made "home made" gages, again checked using wires. There is a measuring system out there called "Gagemaker", very over priced, but does work for use with most threads out there. They still won't check special profile threads unless you pay $$$$ for specially ground rolls or points to fit the thread.

As for the triangles, I've never used them, I know of machinists that had them in their tool box. I recall the corners on them were radius according to the range of thread pitches they were used in so you did not bottom them out in the root of the thread when measuring the P. D..

For myself, I have thread wires that I use most of the time and I also have thread mics for vee threads up to 3" in diameter. Most of the time, I'll thread to a nut or mating part, making sure I put a little slop in the thread. And If I'm in a really big hurry, I'll throw a die nut up in the lathe and chase out the last little bit of thread to get it to size.

 

[Tony Wells]

Thread wires are designed to contact as closely to the pitch line as possible, and provided the flank angles are correct, give a measurement of the pitch diameter. I've used them for years, PeeDee brand. I wonder if they still offer a warranty against losing one. They used to.

Thread mics always seemed to me to be more of a comparative measurement. Not a fan. I was always interested in the PD more. I can measure the Major easily enough, and the thread depth and hence get the Minor diameter. That leaves the lead, which I have a gage for, the flank angle (determined by the tool, unless you have some weird CNC glitch), and the crest and root radii/truncation. Then a sharp eye or a comparator is really handy......but I digress into the commercial world.

I often make soft gages for a small run, even to the point of making a set plug for machining a ring gage. But even go/no-go gages don't measure everything. That's a whole discussion of its own.

My bottom line is I have thread triangles, never use them. I use wires a lot, and if I don't have a "real" thread gage and don't want to buy one, I make a soft gage. I don't have or feel I need thread mics.

I do have and use parts of the Gagemaker system Ken referred to, and although it's pretty good, there are some pitfalls there too.

 

[Bob Korves]

BTW, you can take your threading work to the mating part to test it if you thread it between centers. A verified fit always trumps a fussy measuring method in the H-M world... 8^)