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Seems I'm all screwed up.

If it was a low precision nut, it might 'suddenly' bind. But unless the nut is made of much tougher stuff than the screw, this pattern is hard to imagine.

If it was a die, then I think only a sudden change in the threads could produce this. Otherwise the earlier threads would be marred by the much harder die - or not at all if the size was too loose. Certainly not to the depth shown
 
Did you use a die or a nut?

Both - first the 3/8-24 nut which was very loose at first but then jammed as I tightened it. I had made a small Puller for the Taper because I can't access the backside to release it. As I tightened the nut on the Puller bracket, I didn't notice that it was deforming the threads because high turning force is normal on a Puller. But after the MTaper popped loose, the nut would not loosen easily and damage was evident. I was pissed and cursed a few people I don't know.

Then I tried to fix it with a die which only made the cross threading worse.

That's when I stopped and started diagnosing the problem.

The seller has offered to discount the part and let me repair it and I have countered their offer with a deeper discount because I can get 100% back from Amazon albeit still having to buy something else to replace it.
 
Was it a regular nut? (home depo, rona etc.) or a precision nut? It still looks like a defect
 
It was a pretty run of the mill nut - nothing special. Originally, it was installed on a 3/8-24 bolt.

It does look like a defect. If my measurements are accurate, and I have no reason to doubt them, it is defective or at least not as described! LOL!

I should add that it looked fine when I took it out of the box it came in.
 
I have a small bucket with a handful of yet to be determined bolts from Asia, not SAE, not metric, they are who knows what? They are close to a standard thread pitch, but then the error accumulates as you move down the thread.

How the heck did you manage to collect a whole bucket? I maybe see one every 5 years. And each time I see one it's another trip down the rabbit hole to figure out what it's all about. A full bucket would have driven me insane!

Be nice you guys......
 
Foot in mouth all screwed up kid with an empty bucket here....

Well I'm all done the back N forth through Amazon messenger with the seller.

Amazon says they are in the USA, but they conversed with me in French.

I tried to switch the conversation to email, but Amazon stripped my Email address from the chat despite numerous attempts to hide it. Pretty amazing really. Even separating it into components each in a different sentence got caught.

Told them what was wrong. They offered me a 25% discount to keep it.

I declined, reminded them that Amazon would give me 100% to return the product, and said I would keep it and fix it if they gave me 75%. I figured they would counter with 50%.

Instead they just refunded the 75 and told me to keep the arbour. No connection to manufacturing. So that's that.

I tried......

Keeping in mind that what I originally wanted was a small diameter centering arbour for my rotary table that could also be pulled by the stud, I think I have two choices:

1. Turn the end down to a 5/16 fine thread stud or even 1/4-28 if necessary.

2. Drill it out and put a stud in there - prolly a 3/8-24 like it was supposed to be.

In both cases, it will be important to keep the threaded piece concentric to the MT3 taper or the whole exercise is pointless.

Which would you choose and why?

Other ideas?
 
Foot in mouth all screwed up kid with an empty bucket here....

Well I'm all done the back N forth through Amazon messenger with the seller.

Amazon says they are in the USA, but they conversed with me in French.

I tried to switch the conversation to email, but Amazon stripped my Email address from the chat despite numerous attempts to hide it. Pretty amazing really. Even separating it into components each in a different sentence got caught.

Told them what was wrong. They offered me a 25% discount to keep it.

I declined, reminded them that Amazon would give me 100% to return the product, and said I would keep it and fix it if they gave me 75%. I figured they would counter with 50%.

Instead they just refunded the 75 and told me to keep the arbour. No connection to manufacturing. So that's that.

I tried......

Keeping in mind that what I originally wanted was a small diameter centering arbour for my rotary table that could also be pulled by the stud, I think I have two choices:

1. Turn the end down to a 5/16 fine thread stud or even 1/4-28 if necessary.

2. Drill it out and put a stud in there - prolly a 3/8-24 like it was supposed to be.

In both cases, it will be important to keep the threaded piece concentric to the MT3 taper or the whole exercise is pointless.

Which would you choose and why?

Other ideas?
I would do #1. This way you know that your threads are concentic with the arbour.

If you do #2 by drilling and tapping, it introduces a lot of variances. Is the hole straight?; is the tapped threads straight?, is the threaded rod true?

If you needed to have a 3/8-24, I would drill and tap the arbour to a 1/2"-13; red loctite a long enough bolt into it; wait 'til the loctite is fully cured; then turn and thread to 3/8"-24.
 
Here's another one for you:
I wish my name was Schrader. He invented a bastard thread and managed to get it accepted as a standard world wide. His thread is 7.2mm x 32 TPI. 50% of all vehicles in the world use a schrader valve. I have wanted to find a tap for this thread and it is closely guarded and not for sale.
 
I would do #1. This way you know that your threads are concentic with the arbour.


Excellent point. If worst comes to worst, I could always still do #2.

If you do #2 by drilling and tapping, it introduces a lot of variances. Is the hole straight?; is the tapped threads straight?, is the threaded rod true?

If you needed to have a 3/8-24, I would drill and tap the arbour to a 1/2"-13; red loctite a long enough bolt into it; wait 'til the loctite is fully cured; then turn and thread to 3/8"-24.

As above, I'll try #1 first, but I like this new idea. It's the reason I ask for input. Never underestimate the power of ideas from others. I had planned to make a threaded rod with the same thread on both ends. But your thoughts about installing a bigger threaded stub first and then cutting the thread on the remaining stub to the target thread, has the very best chance of producing a very concentric thread large enough to hold when pulling the taper out and still make it possible to machine a stub as concentric as possible.
 
I would turn it down and cut new threads. As you say, if it doesn't work, you can still drill it out.

What I would do is find an MT3 socket and put the part in it. Then machine it so it stays concentric. On my machine, that would be loading it in the quill of the mill, and putting one of the lathe tools in a vice.
 
I would line up the RT on the mill, install the arbour in the RT socket and use the mill to turn down the stub to dimension. This way the stub is concentric with the RT.
 
Here's another one for you:
I wish my name was Schrader. He invented a bastard thread and managed to get it accepted as a standard world wide. His thread is 7.2mm x 32 TPI. 50% of all vehicles in the world use a schrader valve. I have wanted to find a tap for this thread and it is closely guarded and not for sale.
They say it's a Schraeder valve tap but .305 sure ain't 6.2mm.

New 0.305-32 (.305x32) HSS Tap - Schrader Tyre Valve Stem Tap https://a.co/d/froBQnU

I've got a tap I use successfully for Schrader valves but I have a notion it might be a close metric size??? I'll have to go look in the shop.
 
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