dimensions for tensile specimens

[Joe Miranda]

I need to make some threaded tensile specimens. Does anyone have a link or a file of the dimensions for various thread size specimens?

 

[rklopp]

You can buy ASTM E8, and it will have the real-deal standards including threads and gauge section dimensions. It's $78 (yikes, more than double the price a few years back).

 

[Joe Miranda]

RK - you're a genius! Found it - exactly what I needed - thanks!

 

[L Vanice]

I need to make some threaded tensile specimens. Does anyone have a link or a file of the dimensions for various thread size specimens?

I expect few people here have ever seen one, so I took a picture of the ends of two different failed tensile specimens. I pulled them out of a scrap bucket at my engineering school, around 1960. They are some unknown copper alloy and have been in my "brass bar" bin for over 60 years now. The gage diameter has been reduced by the pulling process, but the threads are 3/4-10. I recall the gage diameter was selected to make it a nice round fraction of a square inch to ease calculating the tensile strength with a slide rule. There is a milled flat on one end for taking Brinell or Rockwell hardness readings. The necking down at the fracture point gives a rough visual indication of ductility, but there was an instrument that gave an exact measurement.

Larry

 

[Illinoyance]

We used to make the middle .505" dia. That way the are is erectly .200 square inches. It saved calculating back in the day before computers or programmable calculators.

 

[lastrada]

Here is a quick sketch off of a model I have.

 

[Cole2534]

We used to make the middle .505" dia. That way the are is erectly .200 square inches. It saved calculating back in the day before computers or programmable calculators.

That is one of those numbers still stuck in my head from engineering school.

25.4, 9.807, .505, 32.17, 231, 745, .7854


Ah man, to be back in college.

Sent from my SM-G981V using Tapatalk

 

[BoxcarPete]

That is one of those numbers still stuck in my head from engineering school.

25.4, 9.807, .505, 32.17, 231, 745, .7854


Ah man, to be back in college.

Sent from my SM-G981V using Tapatalk

Let's see: mm/inch, g (m/s²), diameter of a tensile rod, g (ft/s²), the area code for northern lower peninsula, ???, and the bore diameter of a 10 gauge shotgun.

How'd I do?

Now that you put it on paper, .7854 is tickling the back of my mind again... Is it pi/4?

 

[Conrad Hoffman]

Here's a couple useful sites for mystery numbers-
.7854 - Wolfram|Alpha
The On-Line Encyclopedia of Integer Sequences(R) (OEIS(R))

Years ago I thought I found a similar site that easily identified the various physical constants with multipliers and divisions, but I haven't been able to find it again.

 

[Cole2534]

Let's see: mm/inch, g (m/s²), diameter of a tensile rod, g (ft/s²), the area code for northern lower peninsula, ???, and the bore diameter of a 10 gauge shotgun.

How'd I do?

Now that you put it on paper, .7854 is tickling the back of my mind again... Is it pi/4?

Pi/4 indeed!

Others were cu in/gal and watts/HP.

Circular calc were always a PITA until I realized that .7854 is the ratio of area of circle:square given the same diameter and side length. Circles are squares missing their corners.

How much bigger is 3" pipe vs 2"? Could turn it into circles, or just know its 9/4.

Can also view it as the ratio squared. 3:2=1.5 ---> 1.5^2 = 2.25.

This is pretty helpful when determining pipe sizes. Beyond that Im not sure.

 

[Joe Miranda]

Alright - follow up tensile test question. We want to make up some adapters and other useful components for our tensile machine. Anyone know what material is recommended?

 

[rklopp]

1. Adapters need to be stronger than the specimen.
2. If testing in fatigue, adapters might need to be a whole lot stronger than the specimen.

In a normal, non-fatigue situation, 4140 pre-hard would be my starting point. Hopefully you don't end up at Maraging 350!

 

[4GSR]

All of the tensile testing fixtures I've designed were always made of 4130-4145 110-140K yield material. In the range of 28-36 HRC. A few were made of unknown materials, too. We don't talk about them, but they worked.

 

[Joe Miranda]

I have made some from 4140 ph and they have performed fine. I was really just wondering if there was a recommended material by the places that make these machines but they hold that info close to the chest.

 

[Milland]

Ideally the ratio of clamping features to gauge diameter makes it less critical that the clamp elements be very strong. What might matter more is accuracy and surface finish of threads, perpendicularity of features to ensure no bending loads are put into tensile specimens, and consistency of manufacture, so all clamps are functionally equivalent.

I still remember having to tell the (otherwise very bright) grad student I made metal matrix tensile specimens for that the extensometer didn't get clamped to the gauge diameter, but to the two grooves inboard of the threads I'd put in for that purpose.

[Yes, there are some that get placed on the gauge diameter, but these were not]

 

[4GSR]

I'm sure if you buy specimen holders from Instron they are more than likely made from S-2 or S-7 tool steel and harden in the mid 40's on the Rockwell C scale.

 

[rbent]

Alright - follow up tensile test question. We want to make up some adapters and other useful components for our tensile machine. Anyone know what material is recommended?

All depends on the service that they'll be doing and what you are doing. Threaded adapters we use ETD-150 as its easily available in round sizes from McMaster and it's good stuff. Plenty of other stuff is just regular ole hot roll plate weldments. Hydraulic grip jaws are going to be a whole different story than just fixturing to hold something.

Plenty of stuff is made out of 17-4 as well, but also there is plenty of 4140 style alloys in use.

In the end for most of the parts and most of the use there just isn't anything special to it.