Thread sizing

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Lewayne
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Joined: Sun Feb 03, 2019 4:02 pm

Thread sizing

Post by Lewayne »

Hi guys, I have to make a part for something. It needs an external thread on what will be a tube when I drill it out. A matching male thread I have is metric 1.5 pitch but I don't know the size. The outside of the thread tips measures 17.91mm. would that be a 18mm die? And when I turn it, is that 17.91 the measurement I would make the blank before threading it. My old south Bend has no metric capabilities at the moment so I'll have to use a hand die. I'm turning it in brass. I may be pushing my capabilities here but I see no reason why I cant do it.I'm fairly new to this.
I did make two aluminum clamps to hold the battery to my bike frame this weekend and I did that on my mill and they work perfect, and I didn't make a single mistake that caused me to chuck one and start over. I was so pleased. so I'm trying something else.
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Harold_V
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Re: Thread sizing

Post by Harold_V »

It would be reasonable to conclude that the major diameter is 18 mm. That's assuming the piece in question isn't a bastard, and 16 pitch, as the difference between 1.5 mm and 16 pitch is very small (a little more than three thou per inch). If the male piece you have is a good fit, it's most likely metric.

H
Wise people talk because they have something to say. Fools talk because they have to say something.
Lewayne
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Re: Thread sizing

Post by Lewayne »

That's what I thought too. What size should the blank be before threading for an 18 mm thread?
earlgo
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Re: Thread sizing

Post by earlgo »

Lewayne, it appears to me you need to find a copy of "Machinery's Handbook" published by Industrial Press. In it you will find all the information you will need, and some you will never need. :)
The Major diameter of an M18x1.5 screw is 18/25.4 or 0.7087
Good luck with your project
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
pete
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Re: Thread sizing

Post by pete »

Yep I'd 100% agree with Earl about the necessity of having a copy of that Machinery's Handbook. Standards were developed for extremely good reasons and make fitting your own parts to anything commercially produced so much easier. For the average home shop any post 1940's edition would be ample for $20 of less on Ebay. The newer editions cover more metric, but with the trade off of loosing a lot of manual machine information. Trusted reference books should be considered as tools and just as important as the equipment and tooling were using them alongside of.
earlgo
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Re: Thread sizing

Post by earlgo »

Lewayne: While we are suggesting books, perhaps you would be interested in the South Bend version of "How To Run a Lathe". It it the third one in the list in the link.https://all-med.net/pdf/how-to-run-a-lathe/. My apologies if it appears to be a bit of a beginner's book, but there is a lot of good info in the tables and illustrations, although some may be quite out dated. I am sure quite a few of the members here have a copy to rely on from time to time.
Here is another website with a downloadable version. https://ebooksdownloads.com/pdf/how-to-run-a-lathe
Hope it helps.
--earlgo
Before you do anything, you must do something else first. - Washington's principle.
Lewayne
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Re: Thread sizing

Post by Lewayne »

thanks guys . your right, i do need the book and I do have a number of the south bend books
pete
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Re: Thread sizing

Post by pete »

The longer you have a copy of the Machinery's Handbook the more you'll refer to it. While the South Bend book is a good one and I have a copy. Much better is doing a Google search for the Textbook of Turning PDF originally produced by Hercus Lathes in Australia. Afaik they were building licensed copies of the South Bend lathes with there own ideas and improvements much like Boxford Lathes did in the U.K. Both company's produced arguably better lathes than the original SB designs were. That PDF is vastly better and much more in depth than what the South Bend book was ever meant to be.

The MHB gives you the reference standards still in use today for interchangeable parts, maximum speeds, feeds, cutting tools etc. But it won't teach you all that much about the actual machine tool operation or set up. If I could go back 40+ years and still know what I do today I think there's at least 3 more books for roughly $100 total I'd immediately buy as the best information I know of for anyone with at least a lathe and wanting to learn as much as possible.

https://www.teepublishing.co.uk/books/i ... op-manual/ As a general reference for very high quality projects and detailed how/why one might chose one method over another. It's the one single source I've seen so far with the most user friendly information crammed into it. I've heard but don't know for sure it's about to be discontinued, so if your at all interested I wouldn't wait to order one.

https://www.teepublishing.co.uk/books/w ... the-lathe/ for exhaustive and detailed answers to any thread cutting question you might ever have. I've been in a few commercial shops that even had a copy of it in there office.

https://www.teepublishing.co.uk/books/w ... e-lathe-1/ For a really good work holding answer book and I can safely say it's not quite as simple or obvious as it seems once the parts start getting a bit more complex. It also taught me that a face plate can give you options no 3 jaw scroll or 4 jaw independent can offer, yet you rarely see them mentioned anywhere else.

And either of these https://www.teepublishing.co.uk/books/w ... the-lathe/ if your ever forced into using a lathe for minor light milling. Or this one if at some point you get or already have a vertical mill. https://www.teepublishing.co.uk/books/w ... -workshop/ Anything else after those are the finer details you can pick up from forum posts, YouTube video's and more detailed and specific reference book subjects. Dividing, indexing, gear cutting, grinding, honing etc. I also haven't ever found a cheaper source for those books than the one in my links. Every Ebay re-seller for the exact same thing always wants multiple times more.
chief
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Re: Thread sizing

Post by chief »

Lewayne,

Plus one on recommending the Machinery's Handbook, but a follow up recommendation.

Unless you are into just having the latest and greatest, I recommend you find an older edition, not the newest published version. If you look on eBay or at other used book sources, it will be much cheaper and still have all the information you will need. New edition is #31 and over $100, but on eBay recent versions can be had in the 20-30 dollar range

Terry
10 Wheeler Rob
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Re: Thread sizing

Post by 10 Wheeler Rob »

Most male threads are a few thousands less than the nominal diameter when you measure them. Starting with that blank size will take a lot less force to turn the die. This is what I do for my hobby projects.

Rob
whateg0
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Re: Thread sizing

Post by whateg0 »

Harold_V wrote: Thu Jul 29, 2021 1:24 am It would be reasonable to conclude that the major diameter is 18 mm. That's assuming the piece in question isn't a bastard, and 16 pitch, as the difference between 1.5 mm and 16 pitch is very small (a little more than three thou per inch). If the male piece you have is a good fit, it's most likely metric.

H
I believe that's 3 thou per thread, not per inch. 16 threads at 1.5 mm is 24 mm, or 1.4 mm short of an inch.
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Harold_V
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Re: Thread sizing

Post by Harold_V »

whateg0 wrote: Tue Aug 03, 2021 8:19 am
Harold_V wrote: Thu Jul 29, 2021 1:24 am It would be reasonable to conclude that the major diameter is 18 mm. That's assuming the piece in question isn't a bastard, and 16 pitch, as the difference between 1.5 mm and 16 pitch is very small (a little more than three thou per inch). If the male piece you have is a good fit, it's most likely metric.

H
I believe that's 3 thou per thread, not per inch. 16 threads at 1.5 mm is 24 mm, or 1.4 mm short of an inch.
Ooops!
Yes, you are correct. I was wrong. The three thou difference per thread would be quite obvious. Thanks for the correction. :wink:

H
Wise people talk because they have something to say. Fools talk because they have to say something.
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