Anyone know how threading rolls work?

[rotorhead]

Hi Lads,

Do any of you knowledgeable Gents know the principles of thread rolling?

I'm contemplating building a set up for doing just that, after seeing how much is being asked for such gear on fleabay.

I'm working blind on this one, I've Googled thread rolling, but not been able to find any specifics.

Thanks in advance for any pointers...

[philf]

Hi rotorhead,

Have a look at http://www.reed-machinery.com/pdf/thread-and-form-rolling-tech-data-master.pdf

It talks about several different methods of rolling threads.

I've only had experience with rolling threads on bike spokes which I've had mixed success and failure with. If I start with no existing thread I get 50% 2-start threads. If I start with a few threads already there (e.g. when I've cut down a longer spoke) it works OK.

Mine is like:



The grooves aren't helical - they're individual grooves. Each roll is angled at the helix angle of the thread.

The big nut runs on a slightly tapered thread and the body is slit so that tightening the nut closes up the dies.

Cheers.

Phil.

[rotorhead]

Hi Phil,

Thank you for the reply and PDF, I've actually come across a thread rolling head similar to your picture, on fleabay for $25 delivered, so I've sent for it figuring £15 isn't too much to lose.

Your explanation of your head gives me a lot of thought to what I might achieve.

What I had envisaged was helixed (or is that helied) rolls (threaded to a given pitch), with differing start points, or positioned at spaced out increments.

I remember when I was a lad, that our localish (about 20 mile away) Motor Cycle Engineer/Dealer (bloke called Barry Ladlow), had a bike spoke threading tool, it held the spoke in a clamp opposite a multi roller head, which was cranked onto the blank spoke, it worked perfectly everytime as I recall.

Thanks again Phil.

[David Jupp]

Can't help much with building them - but do know from application in industry that getting the starting diameter for the stock to be threaded correct is critical for good results.  When rolling 3/8" UNF LH threads on high pressure piping, test pieces were used to arrive at optimum starting diameter.

[Lew_Merrick_PE]

Back in the late-1960's & early-1970's I worked on the (USAF/NASA) project that retooled the aerospace screw/bolt industry to rolled thread operations.  I was a lowly machinist and was involved primarily in the fitting & adjusting of the various slides that allowed on (4-line) machine to make (and changeover) four lengths of screws using three sets of dies & rollers.  (The .2500-20UNRC X 1 inch line could produce 1.2 million fasteners in 40 hours.)

The problem you are facing is that the rolling of external threads is dependent upon: material, material condition, material size, temperature of operation, and lubrication of the thread rollers.  In the threading stage of operation, the material was advanced to a specific position, heated up fairly hot (1100°F for 4340 steel, as I recall), and rolled to thread under a wash of lubricant/coolant.  Other materials had other preset diameters and were heated to different temperatures.

Poisson's ratio for the material plays a rather large role in this process.  There was a lab on site that did nothing but determine that value to 4 decimal places for each material/size combination.  (This was my introduction to the concept of Poisson's ratio.)  Even with all the analytic power that the USAF & NASA could apply to this project, there was a lot of trial & error involved in the final operation set.  It was a regular sight to see a set of 6 inch or 10 inch rollers explode when over-stressed...

[Henning]

Here's some YouTube- vid's explaining some of the process and also some manufacturers of such equipment if it helps: [ Invalid YouTube link ]thread+rolling