CAD Forum

Nut and Bolt is there to fasten the parts together. What is the purpose of having tapper thread? In my view, it will tend to get loose quickly in the course of time.

Plugs, pipes, etc. Can create gas tight connections without adding any seal, except some lubricant. (Have a look at NPT, NPTF, R, Rp, Rc.)

Oil and gas, ground drilling attachment.
Easy disconnect in dirty environment is one benefit.

Maha Nadarasa wrote: ↑Thu May 20, 2021 7:29 am Nut and Bolt is there to fasten the parts together. What is the purpose of having tapper thread? In my view, it will tend to get loose quickly in the course of time.

Taper threads act as a both a nut and bolt as well as a sealing element all in one. With a taper you can put a male and female together and just keep tightening until it seals. Without an additional sealing element that is more difficult to do with straight threads because the relationship to OD and ID remain the same regardless of torque applied.

They are used largely in fluid fittings and essentially in standard size the designation is NPT which stands for National Pipe Thread.

They don't come loose anymore quickly than a straight thread. Once a straight thread comes loose the nut/Bolt Spins freely. Only difference is that depending on thread length of a straight thread a taper thread comes out with fewer rotations because the threads are clear completely after some number of turns regardless of length.

Maha Nadarasa wrote: ↑Thu May 20, 2021 7:29 am Nut and Bolt is there to fasten the parts together. What is the purpose of having tapper thread? In my view, it will tend to get loose quickly in the course of time.

There is also an interference fit which tends to help lock it in place. But as mentioned its for sealing against leaks of gas/oils, etc. We use the NPT type threads for large hydraulic jacks. Also have pipe plugs and bleeders valves. None of these have any sort of locking issues, they are just torqued down.

MJuric wrote: ↑Thu May 20, 2021 10:03 am Taper threads act as a both a nut and bolt as well as a sealing element all in one. With a taper you can put a male and female together and just keep tightening until it seals. Without an additional sealing element that is more difficult to do with straight threads because the relationship to OD and ID remain the same regardless of torque applied.

They are used largely in fluid fittings and essentially in standard size the designation is NPT which stands for National Pipe Thread.

They don't come loose anymore quickly than a straight thread. Once a straight thread comes loose the nut/Bolt Spins freely. Only difference is that depending on thread length of a straight thread a taper thread comes out with fewer rotations because the threads are clear completely after some number of turns regardless of length.

Have you never heard of JIC?

https://www.daltonhydraulic.com/1-2-fem ... wivel-4638

https://www.mcmaster.com/50695K266/ (They also work for hoses and adapters, not just tubing.)

From finger tight to 5000 psi in less than half a turn!

There's a reason god invented o-rings.

And God damn we need to design proper o-ring grove. One time use.
Need to add torque spec to bolts.

SPerman wrote: ↑Thu May 20, 2021 11:34 am There's a reason god invented o-rings.

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Have you never had a numbskull who thought tighter is always better? (note the past tense)

And yeah, I've seen split #4 JIC hose ends too.....

I spent the majority of my adult life working in Nascar. I know all about "tighter is better."

mike miller wrote: ↑Thu May 20, 2021 11:22 am Have you never heard of JIC?

https://www.daltonhydraulic.com/1-2-fem ... wivel-4638

https://www.mcmaster.com/50695K266/ (They also work for hoses and adapters, not just tubing.)

From finger tight to 5000 psi in less than half a turn!

Yeah, use them all the time...they don't seal on the threads, and thus "Another sealing element". Sealing straight threads with the threads only is a fools errand at best.

mike miller wrote: ↑Thu May 20, 2021 11:43 am Have you never had a numbskull who thought tighter is always better? (note the past tense)

And yeah, I've seen split #4 JIC hose ends too.....

I've seen split #6 JIC hose ends. Guy said, "Yea, I just kept tightening it and it suddenly split!". Well then you obviously made it too tight!

Attached are some JIC and pipe fittings I modeled.