Types of Thread Rolling Dies
Speed-up Dies
Speed-up dies are available for smaller sizes up to about 3⁄4 " diameter work. These are usually 1 1⁄2 , 2, 2 1⁄2 or 3 times speed-up, or any ratio in between. The work piece does not rotate any faster than with annular ring dies, but feed rate is increased in proportion to percentage of speed-up dies used. Commonly used for all threaded rods from 1⁄4 " to 3⁄4 " diameter.
Helical Slow Feed Dies
Helical slow feed dies are used for high helix work where part of the helix angle is ground into the die and the spindles are tilted for the rest of the helix angle. A coarser pitch can be rolled on a smaller machine than with annular ring dies. It feeds through at a slower rate, giving dies more time to form thread.
Annular Dies for Thrufeed Rolling
Flat Taper
General rolling of mild and alloy steel. Dies must be opened for starting each bar. This type of die is less expensive, stronger and used whenever possible over Form Ground Taper.
Form Ground Taper (FGT)
Front rills are stepped down with thread form. Can be used for all types of rolling material. Dies must be opened for each bar. This taper would also be used when rolling certain materials (certain types of stainless, high lead content in the parts, etc.) Where the regular Flat Taper would cause flaking of the thread. Also can be utilized when there is a need for re-rolling.
Short Flat Taper
Very short taper to minimize runout of threads if rolling close to a shoulder.
Short Form Ground Taper
For material where FGT is needed and runout threads must be kept to a minimum.
Flat Taper Continuous
Longer Flat Taper of lesser degrees where dies stay closed and one bar is fed against the other for continuous rolling.
Form Ground Taper Continuous
Use where FGT is needed and when feeding one bar after the other with head staying closed.
Double Step-off
Partial Form Ground Taper with Flat Taper in front. Used for continuous rolling where dies stay closed. This type is used if flaking would occur with Flat Taper for continuous thrufeeding.
Back Rills Stepped Down
When necessary to prevent back of dies from cracking out and necessary to prevent lead change from material exiting back of dies.
Either of the Flat Tapers are the strongest taper if they can be used without flaking. Flat Tapers cannot be used for re-rolling. Form Ground and Double Step-off tapers can be used for re-rolling if necessary.
On annular thrufeed dies, the back one, two or three rills can be stepped down when required. This prevents breakage of back rills when rolling bars through dies without opening dies. It also minimizes lead change at rear of dies when opening dies while a portion of work is in dies.
Continuous rolling works best on 8 P. threads and finer, or for diameters 2" and smaller.
