My Favorite Thread Calculator -Any thread you can dream up.

[Lloyd-ss]

Once I ran across this calculator, (and this might be old news to many of you) I never go anywhere else. You can choose from a comprehensive drop-down list, or put in your own diameter and pitch and class. Once you hit the Compute button, you end up with more info than you know what to do with.

http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx
There is also a metric version

http://theoreticalmachinist.com/Threads-MetricMProfile.aspx
The MOW (measurement over wires) is super handy for larger diameter threads. It gives the dims for best wires, but also lets you choose a particular wire size that you have on hand.
I make a lot of thin wall high pressure air tubes (240 bar) with threaded plugs and o-rings in the ends. Usually, standard threads don't work, and this calculator lets me design the thread that most safely suits the situation.

 

[john_1]

Thanks, was not aware of this site. I to have occasion to produce high pressure lines in past have resorted to calculator and machinist handbook.

 

[yelcho]

Once I ran across this calculator, (and this might be old news to many of you) I never go anywhere else. You can choose from a comprehensive drop-down list, or put in your own diameter and pitch and class. Once you hit the Compute button, you end up with more info than you know what to do with.

http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx
There is also a metric version

http://theoreticalmachinist.com/Threads-MetricMProfile.aspx
The MOW (measurement over wires) is super handy for larger diameter threads. It gives the dims for best wires, but also lets you choose a particular wire size that you have on hand.
I make a lot of thin wall high pressure air tubes (240 bar) with threaded plugs and o-rings in the ends. Usually, standard threads don't work, and this calculator lets me design the thread that most safely suits the situation.

Very useful tapping size tables from Modratec giving range from strong to weak. Modratec used to make model rail signaling but appear to have closed down but website is still running. The part of site labelled MUD has several usefull tables. More shop than designing.

 

[MIKE4444]

EX SITE WELL WORTH A VISIT , THANKS YOU.
MIKE

 

[Oldiron]

Excellent sites and I use them often, often enough that I worry about them going away. Like all things on the internet, nothing is forever. Does anyone know where to find the math behind the calculations? I'd like to duplicate the calculators in Excel so I'd have them when that web site goes away. Bob

 

[Lloyd-ss]

Excellent sites and I use them often, often enough that I worry about them going away. Like all things on the internet, nothing is forever. Does anyone know where to find the math behind the calculations? I'd like to duplicate the calculators in Excel so I'd have them when that web site goes away. Bob

If you look further down on the page that the calculator is on, the author cites ANSI/ASME B1.1-1989 as being the source for his interpretation of the Imperial UN thread form. I dug into that several years ago and some of it does get a bit convoluted. One aspect that I observed, that made me think cautiously, is that most of the thread tolerances and allowances are based on a percentage of the specified thread pitch. So, as the thread pitch becomes smaller and smaller, the tolerances also become smaller and smaller, such that adequate thread strength is maintained. If, for example, you are using a single point thread boring bar to cut a 1" nominal I.D., 48 pitch thread, it might be difficult to stay within the specified tolerance zone. And what I think that does, is effectively reduces the strength or safety factor of the thread, the finer and finer the pitch becomes. Lets face it, a +/-.001" tolerance on a 20 pitch thread is not going to adversely affect the strength too much, but a +/-.001" tolerance on a 48 pitch thread can greatly affect the strength of the thread. It all depends on how accurately you can cut and inspect the threads you are making. What kind of confidence level is needed for the application of the particular thread? Is it mainly cosmetic, or will it be carrying a significant load?
Lloyd

 

[clockworkcheval]

Great site, thanks. A note on thread measurement is that the MOW Measurement Over Wires method is great for external threads but does not really work for internal threads. Elsewhere on this forum I mentioned a one-off solution for a coarser internal thread. It is based on putting balls instead of wires in the thread groove. You can than measure the distance between the balls.

It allows you at least to make a precise copy of an existing internal thread. As measurement instrument I adapted a caliper by grinding parallel grooves on the jaws and glueing small balls on them.



I used a strong and slow curing glue. With the glue still soft I positioned the caliper with balls carefully in the thread to be copied and let it cure under light tension. After 24 hours I got my precise measuring tool, fit enough for the limited use it is intended for. And the caliper is still fit for regular use.

 

[Lloyd-ss]

Clever trick with the balls and the calipers. Measurements with wires or balls requires a certain amount of "art," not just skill. I am never satisfied until I can get a few measurements in a row that are all the same. And that can be difficult.

 

[Thread man]

Using balls and a caliper means different balls for various pitches plus of course a calculation.

For anyone making threads often this might be an interesting and easy solution.

Measuring External & Internal Thread Pitch Diameter - YouTube

 

[Thread man]

Clever trick with the balls and the calipers. Measurements with wires or balls requires a certain amount of "art," not just skill. I am never satisfied until I can get a few measurements in a row that are all the same. And that can be difficult.

"An engineer by nature. The affliction is knowing that everything can be made better."
My YouTube Channel, Airgun Lab

I don't disagree with your post but re your "observation" I'm hoping you don't have kids ☺ My two couldn't be better LOL

 

[Thread man]

Personally I often use this program. Not free but certainly saves me money and time.

https://closetolerancesoftware.com/METhreadPal.html
If my customer wants to measure a specific thread I can give them all the info they need.

 

[davidyat]

I found this free calculator for Imperial and Metric specs:

http://theoreticalmachinist.com/Threads_UnifiedImperial.aspx