'Custom' Tool question: Measuring Manifold nut inside angles?

[T. Cotten]

Folks,

I encounter a lot of different manifold nuts of a lot of different models, and it seems now some reproductions vary significantly from OEM on the inside angle.

It is easily accommodated if it can be accurately measured.

This is posted in "Custom Tools" because I probably must make the instrument, but I haven't a clue what it would look like.

Any ideas?

Thanks in advance as always,

....Cotten

[T. Cotten]

So then,....

How would a "pro" measure it?

Geometry isn't working for me.

....Cotten

[MMasa]

With a CMM.
MARK

[BigLakeBob]

I would get a rough idea of the angle using a protractor, then I would mount it to an angle block. Put the angle block on a sine plate and adjust it until the angle was parallel with the surface plate. Or cut one in half and use an optical comparator.

[T. Cotten]

Thanks Mark!

What's a CMM?
(And is it affordable?)

And Big Lake Bob!

What kind of protractor, or angle block fits inside of a manifold nut?
(Some are only 1 5/16" ID.)

My customers aren't anxious to cut up their vintage hardware, and cutting up new ones is pretty expensive, particularly if you never know what angle the next batch will be.

The problem arose when a fellow's mass-produced PEEK seals failed in modern nuts.
(I have never had an issue with my machined seals, but then I don't use any of the same parameters.)

So I cut some round stock to 60º, 61º, 62º, etc., inked the bevels, and rubbed them into various nuts, OEM and reproduction.
Two degrees is significant, and apparently enough to make a seal fail.

....Cotten

[exeric]

You could make a casting of the angle, and lip of the manifold nut with Bondo. With careful casting of just a section of the inside of the nut, you might have enough of a sample to measure the angle. I've had this same problem with trying to determine an angle inside a gland nut, or packing nut. . . . Tough nut

[T. Cotten]

I considered sealing wax, Eric!

But the bevel is actually wider than the ID of the threads. I would have to break it out, and once again, we do not want to damage the hardware.

So then I thought if I could put a dial indicator in my toolpost set at 90º to the nut in the chuck, I could measure the geometry accurately enough, but no.
One arm of the indicator is fixed, and cannot follow the bevel.

Perhaps I'll hold it with a spring.

....Cotten

[BigLakeBob]

DSC05681.jpgDSC05682.jpg
Tom, this is the method I was talking about to roughly check the angle, and NO, the protractor is not set at the manifold angle. Just quick pictures to show there is an available means. I like your lathe set up to check the angle, but why not use a standard dial indicator and run it back and forth using the compound while adjusting the angle on the cross slide until the indicator reads '0' all the way across the angle. Looks like a quick easy means to me, great simple idea.

And may I suggest that if you use your lathe setup as you pictured, turn the nut 180*. It will be easier to use an indicator as I said if you are not trying to clear the length of the threads. Basically go from the opposite side.

[T. Cotten]

Thanks Bob!

My protractor lacks a tiny adjustable cross-slide rule like that. I was about ready to cut it up.

I understand using the lathe postholder to read the angle, but you lost me with the 180º flip. Working in the open side of the nut seems easiest to me!

....Cotten

[BoschZEV]

It is easily accommodated if it can be accurately measured.

Depending on what you consider "accurate," a set of angle plates might be all you need:

http://chandcompany.com/insize/misce...s-4003-12.html

They're the right size to insert in that nut and if the internal angle of the nut is the same as the plate the bottom surface of the plate will be parallel to the outside flat on the nut. Up to 5-deg. it only takes one plate, and beyond that two plates held together would give 1-deg. resolution.

Of course, there are more accurate ways of making this measurement, some of which have been mentioned by others, but none are nearly as quick as using these angle plates. Again, whether these plates are accurate enough for what you need depends on what accuracy you need.

[T. Cotten]

Golly BoschZEV!

Just holding a straightedge against the narrow bevel is quite a trick, and squaring it up with my protractor doesn't reproduce.
And locking the nut down on the mill way robbed me of feel altogether.

So I would have to be schooled as to how to stack and apply the plates, unless they are magnetic!
This is one more reason to ask some local mentors, especially if they might have some plates..

At this point I would be happy with readings reproduceable to the degree, although I suspect a half a degree can make a difference in the compression zone on the seal.

....Cotten

[BoschZEV]

So I would have to be schooled as to stack and apply the plates, unless they are magnetic!
At this point I would be happy with readings reproduceable to the degree, although I suspect a half a degree can make a difference in the compression zone on the seal.

To test this I went out to the garage and, after looking for something to test it on, decided on the L00 taper on a lathe chuck. I have my mill leveled, and the door jam should be pretty close to plumb, so I held the plates against the taper with my finger and sighted between the edge and that of the jamb. Eight degrees was too little and 9-deg. (i.e. a 4-deg. and a 5-deg. plate held against each other and against the taper by a finger) looked perfect. I then looked up what the taper really is and found it to be 8-deg 17' 50" (i.e. ~8-1/3 deg).

Since it is easy to see the difference of 1-deg. this way, and since the door jamb easily could be off by 2/3-deg., my conclusion is this technique is good to an absolute accuracy of at least 1 deg. Maybe it's good to 1/2-deg. but I'd hesitate to claim that unless I tried it with a rod in the background adjusted to be perfectly vertical.

As the (modified) saying goes: fast, cheap, accurate -- pick any two. This one gives you fast and cheap. Although, 1-deg. accuracy isn't all that bad (unless your application requires better than that).

[exeric]

I found this site that sells neodymium magnets, and I was thinking; if you could find one narrow enough to fit in the nut, and stick to the angle, you could then stick the base of that magnet to a piece of ground steel to establish your sine. You could then use basic trig, or angle plates, or a protractor to find the angle. As I said, Tom, I've had this problem as well so I am hoping you, or someone else comes up with an elegant solution.

https://www.duramag.com/neodymium-ma...IaAncXEALw_wcB

[T. Cotten]

Well Folks,..

First, I trial-and-error cut some stock until a rubbing showed great contact.
Then I took BigLakeBob's advice, and set up a direct indicator, and adjusted the compound to follow the bevel with the toolpost.

Zero math is a good thing.

Both seem quite accurate, but they do not agree. Not even close.

....Cotten
PS: So I take a bunch of time and measure out three Large Port nuts: The OEM, and two popular reproductions, one park'd and one cad.
The disparity among them wouldn't bother me so much if the measurements didn't reproduce. Looks like a spread of eight degrees.

Hope to average more OEMs before I have to set up for other things..

[T. Cotten]

Ignorance is bliss, Folks.

Now I know things I wish I didn't.

Using BigLakeBob's method, apparently accurate to the half o' degree on my Logan, I busted Liberty's R&D time budget logging the bevels found in H-D models in my stash and inventory.
And regretfully, it appears I shall be measuring all that come in. A couple of degrees variation of the OEM examples is perplexing enough, since I have to cut seals with no room for failure, but the eight degree spread for the reproductions is disturbing.

Indian models will be another forensic time-sucker,
Thanks to all...

....Cotten