Blake,
You have quoted biased sources attempting to get unbiased opinions. There are
many
variables that can influence the microstructure of cut threads as well as rolled
threads. Once the variables are stabilized and consistent results are being
obtained, the final products from both manufacturing methods can be cut, ground,
polished, etched and finally analyzed under a modern metallographic microscope;
then decisions can be made regarding quality. It is possible to produce
excellent
results using either method. Roller die produced threads are only practical for
volume production because of the high cost to produce a pair of dies;
conversely,
quality volume production is really only practical using using roller dies.
For the ultimate in high tolerance quality, roller dies cannot match cutting and
grinding in a CNC machine. Anyone who would make a contradictory statement is
being
silly: roller dies are made using cutting and grinding methods. Cut and ground
head
studs would be prohibitively expensive, but I bet you would be hard pressed to
find
anyone who would accept a rolled camshaft instead of the ground ones we all
admire.
Both methods have their place.
Jim
Bulwinkle wrote:
> George:
>
> <<<snip>>>
> Gonaj@aol.com wrote:
> >
> > In a message dated 1/13/01 8:04:29 PM Central Standard Time, yd3@nvc.net
> > writes:
> >
> > << Cut threads on fasteners are not as good as rolled threads. A thread
> > "rolled" into the shank is similar to forging in that it changes the
> > orientation of the material making it stronger. >>
> >
> > Blake;
> >
> > You need more information before you make such statements.
> > The process of making rolled threads often creates some anomalies in the
>root
> > and tip of the thread. These can seriously compromise the strength of the
> > fastener.
> >
> > George
>
> The following quote is from: Thread Rolling Inc., 34 Cedar
> Street, East Hartford, CT 06108, URL http://www.threadrolling.com
>
> "Thread rolling is the preferred method for producing strong,
> smooth, precise, and uniform external thread forms. Thread
> rolling is different from other types of threading processes like
> cutting, grinding, and chasing.
> "Thread rolling is a cold forging process. For the best quality
> threads, it is performed on precision ground blanks. When less
> critical threads are required, the blanks may be produced by
> other means like turning, extruding, or heading. The blank
> diameter of a rolled thread is at the pitch diameter, a
> theoretical point between the major diameter and minor diameter."
>
> The following quote is from: Rolled Threads Unlimited, LTD., 1404
> Pearl Street, Waukesha, WI 53186, URL,
> http://www.thomasregister.com/olc/rolledthreads/custom.htm#top
>
> "In thread rolling, the material is compressed, not cut away,
> creating a stronger thread, and obtaining a much higher
> micro-finish on the flanks. These diagrams indicate a rolled
> thread's superior resistance to stripping. The rolled thread's
> grain structure is not severed in any way, but is, instead,
> reformed in unbroken lines that follow the thread's contours.
> Therefore, for a shear failure to take place, it must occur
> across, rather than with the grain."
>
> Also try http:\\www.edsmfg.com
>
> In several sites that were checked regarding grading of bolts,
> nothing was mentioned about difficulties with rolled threads.
>
> Now, George, where is there information showing that rolled
> threads are inferior?
>
> Blake
> http://albums.photopoint.com/j/AlbumIndex?u=1536873&a=11674710
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