What kind thread is taper with 16tpi 3

[Shiann]

Hello everyone, I’m not an experienced mechanical engineer.
I came across a thread I couldn't recognize and I didn’t find related information in 27 edition machinery’s handbook.
It’s an external taper thread however it has 16 threads per inch.
One end OD is around 4.1034” and the other end OD is around 4.0285”. The thread length is around 0.900”.
A photo is attached.
What kind thread is this and where can I find information?
Thank you so much.
Shiann

 

[DiamondDave]

Is that a plug for blanking pipes?

Can't remember off the top of my head as I rarely work with pipe threads but it could be BSP(Taper) or NPT(Tapered) Do you have a zeus book you can consult?

http://en.wikipedia.org/wiki/National_pipe_thread

http://en.wikipedia.org/wiki/British_standard_pipe_thread

Sorry I can't be more help mate, I'm just going out so ill let you do the maths

 

[DiamondDave]

Meant to ask what do you mean by thread length?

 

[Shiann]

Hi DiamondDave,

It’s similar to the plug for blanking pipe.
At first I thought it’s a NPT, but when I check the table the thread per inch is 8 instead of 16.
So I got confused.

That's okay. Still need to thank you for taking the time to read my problem and post the links.

The thread length I talked about is the external thread appears on the part as the picture showed.

Shiann

Sorry for the bad English.

 

[Oldhydroman]

There is every possibility that the plug is a bit special and doesn't conform to any particular national or international standard.

First you need to check that it is actually 16 tpi and not 1.5 mm pitch (=16.9333 tpi). If you don't have a screw pitch gauge to hand try offering up a bolt with a known pitch and see if you can get the threads to mesh properly. A metric coarse M10 bolt has a 1.5 mm pitch, and a 3/8" UNC or a 3/4" UNF bolt has 16 tpi.

If you can identify the thread as having a 16 tpi pitch you can then check if it has a 60 degree flank angle (UN style) or a 55 degree flank angle (Whitworth style). Offer up a thread of each style and of the right pitch and look through the gaps at the interface (a loupe might be useful). You'll struggle to get one outside a British or Indian scrapyard, but a 3/8" BSW, a 1/2" BSF or a 9/16" BSF thread has 16 tpi and a 55 degree flank angle.

The taper of the thread is unusual as well, a typical tapered thread (NPT, BSPT, Metric Taper) has a taper of 1:16 (an angle of 1 deg, 47 minutes) - yours works out at about 1:12. This makes me think it's a home brew thread.

I suppose it could be a tapered version of a 4"-16 UN male thread used for plugging a very stretchy, or previously stretched, 4"-16 UN [parallel] female threaded port, and the first part of the thread (which would have had a major diameter of 4") has been omitted. Similarly, if the pitch were metric, it could be a M100x1.5 tapered thread with the first part omitted.

If you could tell us what the part is then that might help.

PS. Your English is just fine.

DOL

 

[Shiann]

Thanks Oldhydroman,
I will check to see it's 16 tpi or 1.5 mm.
Unfortunately, I don't have proper tools.
Also I will try to find what what the part is.
Shiann

BTW does NPT has 2 starts thread?

 

[Oldhydroman]

No, just the one thread start for NPT.

The screw pitch gauges are common enough in some realms but obviously not yours which was why I suggested using specific standard bolts as "gauges".

DOL

 

[DiamondDave]

Hi Shiann, Your english is fine mate.

Can I ask why you need to know what it is? Do you need a replacement part? If its a one off do you have a machine shop you can use to perhaps make a one off copy? Is their a lot of plant in your work place with those threads?

 

[racookpe1978]

If the threads are a significant problem - cut them off, and replace with a threaded end piece compatible with a "purchasable" threaded end. Weld the replacement threaded end on the cut-off stub with a socket weld, a union, a butt-welded piece, or re-thread the cut off end.

 

[Cockroach]

I think it may be a bastard thread. Maybe an EUE thread form, except 16 Rnd rather than 8 Rnd. But the taper is 0.500 TPF, looks like an oilfield thread. Really hard to say by a photograph.

I've done this on ocassion, make my own premium thread in order to mitigate copy-cats from stabbing into my equipment. I think it is similar to the Line Pipe thread, except 4 1/8 16 Rnd @ 1/2 TPF EUE thread form.

My best guess.

Regards,
Cockroach

 

[Shiann]

To everyone,
Sorry for all the trouble and I’m very appreciated all your help and concern.

To Oldhydroman,
Thank you for the help. Yes, I knew you suggested using specific standard bolts as gauges. I meant I don’t have proper tools for angle.
And the thread is 16 tpi.

To DiamondDave,
It’s for the reference drawing. Need to keep all the samples in file.

To racookpe1978,
Thanks for the suggestion, it’s for reference drawing. I just need to keep record for the thread.

To Cockroach,
Thanks to your guess, I can use it as a reference to put in the drawing.