Materials suitable for thread rolling
JBO thread rolling dies are suitable for materials that can be cold formed and that have a minimum elongation of approx. 8% coupled with a tensile strength up to approx. 900 N/mm2.
Preparation of workpiece
The blank diameters for thread rolling quoted here are approximate, as the properties of materials differ. If necessary, the blank diameter should be increased in steps of 0.01 mm until the thread profile is nearly fully formed. Any further increase in blank diameter overloads and hence damages the tools. Please observe the threadmajor-Ø tolerance. (see Thread-ABC ).
The workpiece must have a 15–20° chamfer to enable the thread rolling dies to start easily. Both chamfer and blank diameter must run concentrically.
The transition between the blank diameter and any undercut at the end of the thread should be at an angle α of approx. 30°. A 90° undercut causes chipping of the thread rolls and must therefore be machined after thread rolling.
Rolling speed
We recommend thread rolling speeds ranging from 20 to 50 m/min. The top speeds are suitable for brass and bronze and medium speeds for free-cutting steels.
The lower speeds have to be used for steels that are difficult to form. Adequate lubrication with cutting oil is necessary.
JBO thread rolling dies have thread rolls with lead profile
A more accurate thread profile and a more accurate pitch are thereby achieved. With materials that are difficult to form, the lead profile also extends the life of the thread rolls.
Instructions for setting RSV
adjustable thread rolling dies mounted in RSV 2 to 10 thread rolling die holders.
1. Mount rolling die in holder, screw on nut till die has been centralised and butts lightly up against the holder. Lock adjustment with locknut.
2. Turn workpiece outer diameter to guide line blank diameter, roll thread, check effective diameter.
3. To correct the thread dimensions, first adjust the effective diameter with the nut. Then correct the thread maximum diameter by altering the blank diameter in accordance with the procedure described in ”Preparation of workpiece”.