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07-06-2010, 08:38 AM #1
Internal/External diameter threading chart
Does anyone have a chart of the correct diameter a part should be for internal / external threading?
For example if you want half inch threads you should bring the OD to XX size.
I was hoping to blow up a chart and laminate it for my garage.
07-06-2010, 09:24 AM #2
07-06-2010, 09:39 AM #3
This looks pretty accurate.
Tap Chart UNC/UNF Threads - provides tap sizes, drill sizes, pitch, (threads per inch) basic major diameter, basic effective diameter, basic minor diameter of external threads, and basic minor diameter of internal threads for UNC/UNF threads
I have attached a pdf if anyone wants to print it.
07-06-2010, 09:48 AM #4
Cleveland Twist Drill
Cleveland makes a poster size wall hanger made of heavy plastic. You should be able to get one free from a Cleveland distributor.
07-06-2010, 09:58 AM #5
Another column I find handy, though it has to be customized a bit, is one telling how far to crank the compound at 29-30 degrees, to get the desired pitch diameter. It's dependent on whether the tool is perfectly formed or has some smaller tip radius but I find that I use the same tool for almost all my small threads, and I keep it sharpened about the same way, so the results are very consistent.
07-06-2010, 10:26 AM #6
Here is what i use. I thread a lot from 1 1/2 to 3" and never seen a chart that big but i am sure they are out there. Plus i can make custom threads if i want...Bob
Tap Drill SizesBob Wright Metal Master Fab
Salem, Ohio Birthplace of the Silver and Deming Drill, all others are copies.
07-07-2010, 11:47 PM #7
Any chart will only have a fraction of what you want unless it's only a few threads you are interested in.
Sorry for stating the obvious but the outside diameter on a thread (unless it's a pipe thread) is the diameter given in the thread denomination. So a 1/2" thread is 0.5" just as a metric M12 is 12mm.
As to the tolerance then the larger the diameter and/or greater the pitch the larger the tolerance.
With an internal metric thread the bore diameter is the vthread diameter minus the pitch. For example a M16x2 is 16 - 2 = 14mm.
For a standard 5/8-11 UNC find the TPI as a fraction of an inch.
1/11 = 0.0909
5/8 is 0.625
0.625 - 0.0909 = 0.616 which is your bore diameter.
In standard American threads (UNC etc.) and metric threads the tolerance on the outside diameter is about 30% more than the tolerance of the pitch diameter and the bore tolerance is about twice that of the pitch diameter tolerance.
I don't know if this attachment will help or not but it'll give you a good idea of pitch diameter tolerances of various threads and the rest you can do by yourself
It's all in mm but just divide by 25.4 to get inches.
I have much more if anyone is interested
07-08-2010, 10:00 AM #8
Thanks OldMachinist and Gordon B Clarke for these tables, it should take some of the trial end error out of fitting threads for me (I've plotted them both ready to laminate). I have worked out that the external thread needs to be a little smaller than the internal in order for the threads to move past each other but so far have achieved this by trying, resetting and taking another couple of thou off etc. rather than any scientific method.
Gordon - I haven't had a chance to digest the tolerance info given (I design ships and marine structures, not close fitting mechanical parts) - I have seen similar charts before but not been able to work out what they mean. I'll have a look tonight and see if I can get it on my own before I ask you for a dummies guide to tolerances.
07-08-2010, 11:41 AM #9
If you let me know some of the threads you make (or perhaps plan to make) I'll give you all the tolerances and you'll soon get the right "feel" for it.
I had to smile at your reference to "a dummies guide". I once bought one of those books (I refuse to say on what) but I guess I was even dummer than I thought 'cause it still didn't help me (the last one is me, not you)
You'll aso find a great deal of general information if you look at the (for you) relevant pages of Flexible Measurng Systems
Bring on the questions and help make me look smart LOL
07-08-2010, 11:48 AM #10
Jeez Jim, Just noticed the Dumbarton (rock on). I'm originally from Paisley, but as you can see living in Denmark and now a Danish citizen.
Forget the Gordon B. Clarke bit (Gordon is enough) as that was an "accident". I'm so used to being the only Gordon Clarke in Denmark that when I registered I thought Gordon would be enough. Turned out even Gordon Clarke wasn't enough so my middle initial got thrown in. If I could do it over it'd be way less formal
07-08-2010, 12:58 PM #11
The chart I posted was hand typed many years ago from information in Machinery's Hand Book. The handbook has information on almost any thread you will ever need to make. Machinery's Handbook 28th Edition Toolbox | Industrial Press You can find used copies many places and may want have several copies around. I have 3 copies all different editions. Before I retired I kept one at the house, one out in my shop and one in my toolbox at work.
07-08-2010, 01:35 PM #12
Machinery's Handbook has what you are looking for. Most of my work lately is drawn by me and when it comes to threading, I will note the details on the drawing or a seperate paper. I also have the CD for my puter and will print the info and hang it by the lathe. Handy. I even made my own info sheet for the threads which I do the most to show the compound travel for sharp V and unified. That also hangs by the lathe.
Of course, when doing work for customers, the 'wires' come out to assure the proper size.
07-08-2010, 04:38 PM #13
Gordon, I looked through the charts properly and I think I've got it. I'm not used to tolerance classes and when I first came accross the charts showing the relationships between different tolerances they didn't make any sense - thanks to your sheet they do now!
I know what you mean about trying to get your own name on forums, there is one pretty big forum where I managed to register early enough to bag Jim as a username! I'm actually English but I've been in Scotland for 12 years now, maybe I can become a citizen? I started in the shipyards, now in an independent consultancy.
07-09-2010, 01:37 AM #14
11-23-2010, 06:25 PM #15
11-23-2010, 10:47 PM #16
"Dummies books explained to the really dumb dummies"
In a way it's rather like websites made by "experts" who are really good at designing websites but know nothing about the product or customer needs.
Someone that really knows a great deal about a subject tends to forget that not all others know even a fraction, if in fact anything. I remember back in the good old days of floppy discs when I was told that to install I should go into DOS the same way as I usually did. I knew eventually what the letters DOS stand for but never managed to get any further than that LOL
I have an intelligent wife but she isn't technically minded. I usually ask her to read what I write saying, "If you can understand it then everyone can". I'm surprised that those remarks tend to coincide with her having a "headache" in the evening
11-24-2010, 04:14 PM #17
Try these charts