Male and female seating angles?

[rollingcloud]

I believe this is called flared seats. They all around 45 degrees. Should the female angle be manufactured a little bigger than the male angle to avoid interference? I think this would result in a line sealing contact. For example, male angle: 43°/45°, female: 44°/47°.

In my case, the height of the female conical area is only .015''. The height of the male conical area is only .030''. It's a small part. I am thinking to make the male angle to be 44 -45, female: 45 - 46, would this be a good idea?

https://imgur.com/a/jgrEoXd

 

[mfgenggear]

Not understanding this assembly. Is it a critical seal for gas. If it is 45 degrees lapped flat

 

[EdStainless]

You start by asking the designer which surfaces should touch.
You can't get both the tapers and the flats all mate.
Is there a reason that it isn't square with slight chamfers?

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P.E. Metallurgy, consulting work welcomed

 

[mfgenggear]

It is common in automobile valves to be ground and lapped for a seal.

 

[rollingcloud]

It's a section view of an overpressure valve, the shaft in the center moves left or right, the highlighted surfaces are the sealing surfaces. The medium is indeed air. By "45 degrees lapped flat", are you suggesting both male and female should have 45 degrees with lapping tolerances?

Unfortunately, it's a legacy part, and the original owner of the drawing is not with the company anymore.

 

[Jboggs]

First off: if the part is only .015" tall, how is anyone going to be able to measure the difference in 43° or 45°?

Second: if you want a metal-to-metal seal you should go for as much contact area as possible, which means absolutely parallel surfaces. (Otherwise you are going to damage one of them.) And at least one of those surfaces should be made of a somewhat pliable material (brass, aluminum, etc.)

There are standards for flared-type seal joints.

Pressure and media?

 

[rollingcloud]

Jobggs,
I am not sure how they actually measure the internal angles...Maybe the functional tests such as pressure and leakage tests should replace the actual angle inspection for production lots?

Do you have a recommended standard that I can read?

The pressure is around 120 PSIG. Medium is air.

 

[mfgenggear]

Yep that is small. Might be able to view it on an optical comparator. 20 x size or bigger, use a mylar template. I believe its possible.

Yo you have any existing parts.
Might be a screw machine part. They are use to machining tiny parts.

 

[rollingcloud]

mfgenggear,
What about the internal angle inspection? Mold is probably not good enough for this size.

 

[mfgenggear]

Rollingcloud
A cast of two part or a pour of cerolo.
It has melt temp and is poured to fill the cavity.
Some optical comparators have optics
To reflect the geometry.
A very precise and very small ruby probe. And use a cnc coordinate machine.

 

[EdStainless]

I have seen parts like this done on Swiss screw machines.
They were checked by casting with special non-shrinking silicone compound.
We used the same compound to check notches that were 0.015" wide and 0.004" deep.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[rollingcloud]

Thanks guys on the inspection methods.
As Jboggs has pointed it out, any point/line contact would likely to damage the sealing surface. I am assuming that means both male and female angles need to have a nominal angle of 45, or having the same angle within a very tight tolerance, but what kind of tolerance is needed to achieve this?

 

[mfgenggear]

Rolling
How critical will dictate tolerance.
It will be held in ÷/_ degrees

 

[GregLocock]

(sin(45)-sin(44))*.015"= 1/4 thou

Well, I'd certainly have to put my big metrology boots on to measure that. Probably a plug gage and blue would be the simplest approach, and is directly relevant to function.







Cheers

Greg Locock


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[mfgenggear]

Yeah may be blue it and check contact pattern