Newbie question: finding the right size nut

[JeffG]

I appreciate being added to the forum, there seems to be a whole lot of knowledge here. I’m a weekend warrior, with a lot of experience repairing/refurbishing antique furniture so mostly working with wood. I have some decent power tools (almost all vintage), but also a lot of antique hand tools for repairing my oldest furniture. I’ve also rebuilt an auto engine and transmission, done plumbing and lots of electrical work, so have a good collection of hand tools including some tap and die sets that I pull out when needed to chase or cut threads.

When I need machine parts I can usually find what I need at one of the local hardware stores or adapt some scrap metal I have. But sometimes I run into something that isn’t so straightforward. My current puzzle is an old (early 20th century) German brass lamp that is missing a threaded nut for a brass pipe that I simply can’t figure out the size of. And that made me realize that I don’t really know how machine parts are sized - normally I take the piece to match to a hardware store and match it up. I have an old Starrett micrometer so I measured the pipe and hoping someone may know what size it is and where to find a specialty nut to fit.

The thread is very fine, 27tpi, 28tpi or .9mm metric would all seem to work. The threaded part of the brass pipe measures as .659 to .664 in., the unthreaded part of the pipe is .669 to .672in. I thought it could be a 5/8-27 (also called 3/8-ip iron pipe), which was used on some antique electrical fixtures due to conversion from gas, so bought a tap and die that size. But a 5/8-27 nut is too small to screw on the brass pipe; the tap measures .631in. I think 11/16-27 would be too big, but could it be that or metric? If metric, what size? And if it’s not a standard size nut I could find somewhere, is there a way to cut this seemingly custom size part?

[John Hasler]

If it's German it's metric. Might be nonstandard, though, if it's from early enough in the 20th century. The pipe is probably 17 mm. If so the thread may be M17X1.0 .

Get a copy of Machinery's Handbook, preferably an edition that is at least 40 years old. It will contain everything you could want to know about fasteners and other standardized parts (plus a thousand pages of other useful stuff).

[JimF]

You need to determine what the TPI actually is.
Put a piece of white paper behind the part and shine a light on the paper, then measure the thread,
Use a magnifier if needed.

[choprboy]

Given that is it early 1900s, it might not be a standard ANSI/DIN thread. Back then lots of manufacturers and industries had their own threads forms that were similar, but not the same as others. I.e. Armengaud threads, Bodmer threads (German precision instruments), Bourgeaux and Latard threads (Swiss clocks and watches), Löwenherz threads. As John said, being German it should be metric sized... but the thread pitch and angle may not be found commonly today.

[pete]

Yes it could well be metric, not a 100% certainty of that though. As already mentioned, thread standards obviously changed over the years. Also certain industry's used common standards within that industry. There was a constant thread pitch size of 26 tpi used and called I think either a Cycle or Brass thread standard. I'm uncertain of the exact thread flank angle. If it can be positively identified as that 26 tpi then the UK would be the place to search for taps and dies. I'm not sure if it's a thread pitch that's still in common use though. It's sometimes a thread used in older model engineering drawings. Most large machine shop suppliers will usually have a section of in stock but non standard thread pitches for taps and dies. It's doubtful that 26 tpi would be one of them if that's what it is. At least it's diameter is large enough that it could be single point threaded if you have a lathe and it can be set up to whatever pitch it really is.

I just ran a search and 26 tpi appears to have a 55 degree flank angle. https://en.wikipedia.org/wiki/British_Standard_Brass On another hunch I checked here, https://www.victornet.com/searchresults.html?q=26+pitch so if it is that 26 tpi pitch at least some are available off the shelf. Oddly they don't list the flank angle so that still may not work.

[Bill Shields]

Take the pipe to someone who has a set of imperial and metric thread gauges and/or who knows how to measure threads with 3 wires.

You will get to your desired result a lot quicker..and you may well have to get someone to make you a nut.

[JeffG]

Thank you all. I do have thread gauges that came with my tap and die sets, that show me 27tpi, 28tpi and 0.9mm should all work. Unfortunately 1.0mm thread is a bit too large. Although M17x0.9 Looks like it would be a good match, I don’t see anywhere I can find a nut that size (or even one M17x1.0 for that matter). Can I ask where to look online for odd size hardware like that? I only see the same sizes all hardware stores carry.

Also I was wrong about it being German, clearer-head googling indicates it is probably made in US, in about 1911, due to patent marks and company name (Lyhne lamp).

p.s. Also, found a Machinery Handbook online from the early 20th century https://books.google.com/books?id=fTQuA ... ad&f=false but as far as I can tell that only defines the most standard size bolts, like available at most hardware stores.

p.p.s I wish I had a metal lathe, but have only a large wood lathe, way too big and slow.

[mklotz]

You might be surprised at what you can find on Amazon...

https://www.amazon.com/s?k=Nuts&rh=p_n_ ... nut&page=1

An American product from the early twentieth century is unlikely to have metric threads.

17 mm ~= 0.69 inches
1 mm pitch ~= 25 tpi

is fairly close to 11/16 x 24 which McMaster-Carr (the source for all that is good) has...

https://www.mcmaster.com/nuts/thread-size~11-16-24/

Grainger has them too...

https://www.grainger.com/category/faste ... ters=attrs

Just me spitballing but at least those are good places to look once you decide what size you really need.

[hanermo]

I understand the OPs angst.

Soonish, I hope to be able to make nuts for him and anyone else, in these rare custom sizes.

55 or 60 degrees has an effect, as does possible pipe thread, caterpillar thread, and unlikely bbt british bicycle in this size.
I expect to make custom nuts for around 8€ for one and 14€ for two, in that size range - Large Nuts.

I´ve spent over 100k and 10 years gearing up to do this efficiently with a high end industrial refit cnc lathe.
If the OP wants me to have a go, get in touch with me..

[pete]

That's certainly a reasonable cost for something this obscure. But there's not a hope 27, 28, or 0.9mm are all going to work or be even close to being anything close to interchangeable as the OP seems to think. In round numbers there's a .013" difference per full turn between a 27 tpi and 28 tpi thread. That's simply impossible to make work since threads don't and can't function that way. No it's not for a high precision part. But you've still got to identify exactly what thread pitch it actually is, flank angle and possible interference between the threads crest and root shape. And those could be just about anything imaginable. Without providing the male thread as a gauge to whoever might be trying to make the nut, it would be just about impossible to guarantee it's ever going to fit at all. If you just want to jamb something on to hold the parts together and don't care about it's exact function then something off the shelf could be forced on to do so. If that's all you want then it's way outside anything related to real threads or even machining. And if a custom threading tool needed to be hand ground you'd loose your shirt at those prices even with cnc. Without a 100% positive identification of what thread pitch, flank angle etc it is, the jobs impossible no matter how well equipped someone's shop might be. It's exact problems like this that are why we even have those agreed to standards for threads.

[John Hasler]

JeffG could make a mold of the thead and send it.

[Bill Shields]

Where in the world are you...and this pipe that needs the nut?