Concentricity of threads to -A-

Hello All,
I am looking for some opinions on how to measure this callout.

I was thinking of scanning the thread with the appropriate pitch set in auto cylinder...

or

Maybe creating lines on the angles of the threads then creating a circle tangent to the 2 lines. Repeat this many times then create a circle or cylinder out of all those circles to create the PD. (If Possible)

I haven't tried this but it was just me thinking over the weekend of how I will go about this.
I'm not even sure I can create a circle or cylinder out of a bunch or circles radially.

TIA

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DAN_M over 7 years ago

Whenever I am measuring a thread, I like to use a basic auto cylinder with the appropriate thread pitch. Usually works out well.
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DAN_M over 7 years ago

Whenever I am measuring a thread, I like to use a basic auto cylinder with the appropriate thread pitch. Usually works out well.
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acgarcia over 7 years ago in reply to DAN_M

How do you determine what the thread pitch is going to be for the auto cylinder? The help file says the pitch is also know as "threads per inch". So if I have threaded holes with 1/2-20 UN-2B threads, my pitch value on the auto cylinder dialog would be 20?
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DAN_M over 7 years ago in reply to DAN_M

A couple things:

1) "-20" is the number you need to be focused on when calculating thread pitch. all you have to do is 1/20 = 0.3125". Put 0.3125 as the value in the "pitch" area in the autocylinder.

2) the direction of your hits should follow the actual thread pitch. you can make your pitch positive 0.3125 OR you can make it -0.3125. doing so will make your hits spiral upwards or downwards depending on the vector of the hole. what i do is make 2 levels with lets say 100 hits JUST AS A VISUAL AIDE so i can clearly see what direction the hits are going (up or down into my hole" to make that determination. once i am certain that my pitch is going in the right direction, i will then change the amount of hits and levels to suit my needs for the part.
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acgarcia over 7 years ago in reply to DAN_M

1/20=.3125? How is that?
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DAN_M over 7 years ago in reply to DAN_M

SO incredibly sorry, I had multiple browsers open and had a few different numbers flying around in my head as I typed this out. 1/20 = 0.05

That is the value you want to use.

The "20" in 1/2-20 means that there are 20 complete thread revolutions over a 1 inch distance. So your thread pitch you want to use for your autofeature is 0.05".

Again very sorry, going to go poor another cup of coffee now =P
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acgarcia over 7 years ago in reply to DAN_M

lol, not a problem buddy. I just wanted to make sure.

I have a bolt pattern using threaded holes so I wanted to make sure its was measuring as accuracy as possible. Thanks.
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DAN_M over 7 years ago in reply to DAN_M

goodluck! let us know if everything works out for you please!
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