ACME Thread Callout

I'm thinking an Acme thread callout for such an odd size thread would need to be detailed out on paper, with all the dimensions needed to manufacture it.

At 5 TPI, the thread depth for ACME will be around 0.1" (ie 0.2" on diameter)

That doesnot come anywhere between the two dimensions you have mentioned (or are they different? ) 15.745-13.339

If they are different, then probably you can go as per basic ACME designations-

The Thread OD is 15.745, all other dimensions can be calculated based on the standard 5 TPI ACME.

pitch= 1/tpi
Major dia=nominal dia
pitch dia= major - (pitch*.5)
minor dia= major - pitch
addendum= pitch*.25
tooth thickness= pitch*.5
lead= pitch*number of starts
depth= pitch*.5
helix= pitch dia*3.14159/lead (this is the cotangent of the angle)

to calculate the width of the crest or root you need the pcd & minor dia allowances for the required fit.
The minor dia tolerance's are:
For 10 threads per inch and coarser (minus .020")
For finer threads per inch (minus .010")
The pcd allowances are as follows where 'A' =sqrt of the nominal dia:
2G fit= A*.008
3G fit= A*.006
4G fit= A*.004
5G fit= no allowance
The width of the flat at the root of the thread=
(.3707*pitch)- (.259*(minor allowance-pcd allowance))
The flat at the crest of the thread=
.3707*pitch-(.259*pcd allowance)

I appreciate all of the detailed information given. These are valuable to the guys in the machine shop actually cutting the threads. What I have are two different locknut applications, each different sizes. What I am wanting to know is what to put on my drawing pointing to the threaded area. In other thread types one calls out a nominal dimension like 1/2-13 UNC. For the nut that is 15.745 major diameter ACME 3G is it actually shown deatailed as 15.745-5 ACME 3G or would it be shown as 16-5 ACME 3G or 15 3/4-5 ACME 3G? And the 13.339 diameter ACME 3G shown as 13 1/2-5 ACME 3G?

Call whatever you want but give the machinist the major dia - 15.745 and the tpi - 5 and the fit - 3G and the formula. The formula remains constant regardless of the dia bolt etc..

good stuff. GA

I am an engineer and I have never heard of a thread "callout." What is a thread callout?? It seems that you have a ACME threaded shaft and you need to manufacture nuts for that shaft. So what is the outside diam. of your shaft?? You speak of 15.745 inches... can this be your shaft diameter?? Must be a very massive shaft. But whatever your case might be, get yourself a 'MACHINERY'S HANDBOOK." Most libraries carry them. The ACME thread form is treated there in great detail, more than sufficient to make nuts. Hope this helps. A. Berlin P.Eng (Ret)

Mr. Berlin;

You're an engineer, but you've never even heard of a thread callout? Did you never, ever touch any fastening hardware during your entire career? The thread callout is how you specify exactly what fastener you would like used for a particular application. I learned about thread callouts when I was still in high school, before I had any formal schooling in engineering. To say you're an engineer who has never heard of such a thing is quite remarkable!

You could probably find more information in the ASME spec. B1.5-1997(R2009)

Chris

Does ASME B1.5-1997(R2009) have a thread chart in it that go up 16 inch diameter?

I don't have that one.. so I provided a link. It is the nature of these specs that if your business demands compliance to a spec, you have to buy it. but a google search turns up lots of info, and even software to show you all the parameters.

Chris

Thanks Chris. I have a copy of the spec today. It's about 115 pages and I will be reading it today. I will post more as I learn more.

This information may assist:

acme thread calculator http://www.americanmachinist.com/Calculators/ThreadCutting.aspx

http://www.tribology-abc.com/calculators/e3_7.htm

Study Guide to understanding "Machinery's Handbook" http://courses.cvcc.vccs.edu/MAC_Stewart/

Need the dimensional data for ACME threads? Here's a great tool. http://icrank.com/cgi-bin/pageman/pageout.cgi?path=/data/acme/acme.htm&t=2

Download ThreadPal 1.0 free trial http://www.softpedia.com/get/Science-CAD/ME-ThreadPal.shtml

Cheers!

For those interested in ACME threads and Plastic Tooling stories - we had a discussion on "ACME threads and Diamond Dust" at "Skippy and Buzz" -

http://skippyandbuzz.blogspot.com/2010/04/of-acme-threads-and-diamond-dust.html

Good Luck -

Jim