Odd thread size

[tmuir]

I need to make a nut to fix up an old Bing toy steam engine made in the 1920s.

The nut is an odd one as it is 26TPI with a diameter of 9.95mm.

I know they make 26TPI by 3/8 inch taps but this is around 9.525mm so this can't be the correct tap.

This same model uses BA threads on it else where but this is not a BA size.

On bicycle forums I've read of 26TPI 9.9mm threads but thats it.

Does anyone know where I can get a 26TPI by 9.95mm or atleast what is the actual name of of this odd size of thread?

I would say it is 26TPI by 10mm which appears to be an odd cycle thread.
I've found a cycle shop that sells bike parts with this thread on it so the tap must exist.
http://www.sheldonbrown.com/harris/axles.html

 

[tmuir]

Getting closer it would see this thread size is only used on Italian bikes.
I don't know what the thread angle of these are though and I haven't measured the angle on mine either.

 

[Blogwitch]

Tmuir,

You cannot refer to a Metric thread with TPI (threads per inch), it has to be a Metric pitch. It is vice versa as well, for Imperial, it then uses TPI with the diameter in Imperial.

If it is a Metric thread, then the angle will be 60 degs, unless it is BA (loosely based on Metric), then it is 47.5 degs. If Imperial British (BSF, BSW, etc) then it would most probably be 55 degs, or if Imperial American (UNF or UNC) then 60 degs.

Don't be fooled by diameters of threads. Even though it is stated as say 10mm, it can be a fair amount under that for the actual thread OD size. All you can do is measure the pitch or TPI, then using the relevent measurement standards, measure the angle and OD of the thread, then do a guesstimation as to what it is.

So much for worldwide standardisation.


Blogs.

 

[Jasonb]

As Blogs says you are probably looking at an imperial thread and the metric x26tpi is just the way some of teh cycle threads are described.

For example the standard bottom bracket thread is 1.37" x 24tpi but you do see this described as 35mm x 24tpi when it is really 34.8mm major diameter.

You say "The nut is an odd one as it is 26TPI with a diameter of 9.95mm." How are you measuring this or do you mean the thread that the nut goes onto is 9.95mm. If you are measureing the inside if the nut then its 7/16x26tpi BSC which has a tapping size of 10mm

Bit of an odd size but 25/64x26tpi would be close but its a bit of a special

Jason

 

[cobra428]

tmuir
I just did a little math 1"/26tpi = .03846 which rounded up =.039 = 1 mm. So my money is on a 10x1mm thread!!
Tony

 

[Xlmyford]

Hallo.
Here You can see almost any thread around the world :
Threads
Hope that helps.
Btw. 10x1mm is metric fine thread.Very common in Europe.
Cheers,Ralph

 

[cobra428]

Found this place
http://www.hermanscentral.com/product/qual-tech-10-x-1-metric-hex-die-carbon-steel-2985.cfm
Tony

 

[cobra428]

I remember when I was a kid (child not goat :big there was talk of going metric in the US. This was a little while after the Brit's abandoned their imperial system. But :shrug:.
Maybe the cost of changing all the tooling that makes the tooling was to much :shrug:
Tony

 

[Deanofid]

The imperial inch system is a pain!

No it's not! Not for smart folks, at least..

 

[Stan]

I think you will find that the US went to the metric system before Britain did. It is just taking longer to change the things that the average consumer is faced with. All heavy equipment, trucks, cars etc. are made to metric specs but things like a pound of butter or wind velocity will be slow to change.

 

[cobra428]

No weird threads,

Wait a minute....BA, BS, Buttress,Whitworth plus if you own a Machinery Handbook look under threading table of contents.....other threads.... to have your mind blown!
Tony

 

[tmuir]

tmuir
I just did a little math 1"/26tpi = .03846 which rounded up =.039 = 1 mm. So my money is on a 10x1mm thread!!
Tony

If only.

It is just slightly smaller than 1mm, to see the difference I need to use a magnifying glass but its definately not 1mm whilst 26TPI fitts perfectly.
To get the diameter I first used my vernier and then my micrometer. The threaded part comes out at 9.95mm whilst the unthreaded part of the tube in 10mm.

I agree with what blogs says that you shouldn't have a TPI count on a metric thread but its most definately not 3/8 and I can't find any imperial size that fits 9.95 or 10mm.

I'm thinking I may get some 10mm silver steel and finally learn how to turn threads and make a 10mm 26 TPI tap and try it.
If nothing else I will learn how to cut threads on the lathe.

 

[tel]

I'm thinking I may get some 10mm silver steel and finally learn how to turn threads and make a 10mm 26 TPI tap and try it.
If nothing else I will learn how to cut threads on the lathe.

Well, that'd work, but you really should have a nut to gauge the tread you are cutting with. Pity it isn't 10x1mm - I think I have a tap for that.

 

[aussie bruce]

Tmuir mate i think you have to look where the part was made.

Bing toys are german and rigidly metric even in the 1800's .

From a practical point of view in a perfect word a 10mm thread will be 10.00 od
sorry but it does not work that way, as rule of thumb M10 for me will be turned to 9.95mm od then threaded.

Buy the way how long is the part because as the pitches are so close your thread gauge needs to be 3/4 of an inch long to pick up the error.

Do you live near a BMW or Mercedes workshop or Puegoet or Renault will also have them they will have M10 fine nuts and bolts they love to use them in high load situations you can try them as well as the real od bods ie M7 M9 and M11 fine for example.

Good luck with it mate hope this helps

Bruce

 

[Richard1]

Looks like it could be 25/64 BSB that would have 26 TPI, 55 degree thread angle and be within 0.001" of 9.95mm. I have never seen such a thing and have no idea where you would get it though.
Richard.

 

[Blogwitch]

Where was the Bing engine originally made?

That might give you some clue as to the threads being used.

But you must also realise, in those early days of production, they would most probably make their own thread cutting equipment, especially in a non critical manufacturing industry. They might have just made up a thread that did the job, rather than making it a standard size, which might have been a little large or small for the job in hand. The Japanesse were renowned for doing things like that on their early forays into mass motorcycle production, with all sorts of 'special' threads being used.

Your best bet, if you are able, is to single point a thread exactly to the measurements you have, and do trial fits the closer you get to finishing the cut.

Blogs

 

[tmuir]

Your best bet, if you are able, is to single point a thread exactly to the measurements you have, and do trial fits the closer you get to finishing the cut.

Blogs

I think thats what I will be doing.
I've put out a call to a friend in Germany to see if he can turn up an original part else I'm goingt o learn how to turn threads on my lathe and make a tap. :big:

 

[Jasonb]

There are a lot of Bing collectors about so there is no doubt a forum, yahoo group, etc somewhere on the net. Would be worth searching one out and asking on there what the thread is.

Jason

 

[Majorstrain]

I'm thinking I may get some 10mm silver steel and finally learn how to turn threads and make a 10mm 26 TPI tap and try it.
If nothing else I will learn how to cut threads on the lathe.

Hi Tmuir,
If you need some silver steel, I recently purchased a meter of 12 or 14mm (cant remember which and shed is closed up now). I only used 20mm of it. Your welcome to a piece of it if you like.

Cheers
Phil

 

[tmuir]

Hi Tmuir,
If you need some silver steel, I recently purchased a meter of 12 or 14mm (cant remember which and shed is closed up now). I only used 20mm of it. Your welcome to a piece of it if you like.

Cheers
Phil

If I can't get any 10mm I will take you up on that as the biggest I have at the moment is 3/8.
I got lucky a while back and got for just a few dollars meter lengths of silver steel in 1/16, 1/8, 3/16, 1/4, 3/8