Formula to predetermine length growth from thread rolling
Formula to predetermine length growth from thread rolling
(OP)
Is there a formula to predetermine the linear growth from rolling a thread? I have a part made from 4340 steel that will have a 3/8-24 thread rolled for a length of 1-3/4" and I only have .006" tolerance on the overall length which I am afraid will get longer after the thread is rolled. The thread roll will be sublet and obviously be done after the blank has been produced so I must compensate for any growth on the blank.





RE: Formula to predetermine length growth from thread rolling
why not start from thread stock (rather than bar) ?
is the application fatigue sensitive ? or corrosion sensitive ? ... why not machine the thread ?
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
Ted
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
Heck, unless you're being fairly precise with your starting diameter I could imagine this kind of length variation might come from if your start bar is near max tolerance.
Trimming the part after rolling sounds like an idea. Is the geometric or other reason not to do this?
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Formula to predetermine length growth from thread rolling
http://www.youtube.com/watch?v=3kxcw08p_oY
At 2:10 threadrolling starts.
RE: Formula to predetermine length growth from thread rolling
and is the preform diameter equal to the body diameter
rather than the pitch diameter?
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
RE: Formula to predetermine length growth from thread rolling
Ted
RE: Formula to predetermine length growth from thread rolling
Peter Stockhausen
Senior Design Analyst (Checker)
Infotech Aerospace Services
www.infotechpr.net
RE: Formula to predetermine length growth from thread rolling
What is Engineering anyway: FAQ1088-1484: In layman terms, what is "engineering"?
RE: Formula to predetermine length growth from thread rolling
.011/1.75 would give you the expected
expansion per inch of thread rolling.
RE: Formula to predetermine length growth from thread rolling
But from an engineering point of view, I wonder if a guy could get away with Possion's Ration for the three dimensional case of cross sectional diameter reduction? Since the cross sectional geometry is circular, then the two axis orthagonal in the plane of the circle are equal, I only have the longitudinal axis to worry about. The the strain is deformation over original length, maybe something small like 1/64 inch is not out of the ordinary!
Looks like a nice problem this evening over a few glasses of red wine. I will post a solution if I get one!
Kenneth J Hueston, PEng
Principal
Sturni-Hueston Engineering Inc
Edmonton, Alberta Canada
RE: Formula to predetermine length growth from thread rolling
Fudge and wine. That could work.
Ted
RE: Formula to predetermine length growth from thread rolling
With regards to the rolling process: There is some plastic deformation just below the threads surface, the rest is mostly elastic deformation, which means material is displaced, not compressed. The minor hardness difference in the shank compared to the threaded area at sufficient distnace from the actual threads suppoorts this.
My guess is that there will be lenghtening, since the total volume stays the same. The difference in volume being the basis foro the length change?
I'd go for a test. Roll a few and measure them before and after the rolling process. All others methods are educated geusses imo, and if this is so critical, a test is the only way to be sure.