PRELIMINARY INSTRUCTIONS

Check the following.

1) The rams1ide must not have too much play. Place a lever between the ramslide and its pocket and exert pressure by hand. Check play with the aid of a comparator. The maximum play should not exceed 0.004". Make sure to repeat this operation on both ends of the ramslide, testing it at various stages through the stroke.

2) Both die pockets must be clean and devoid of flash or metal chips,

3) Shims (if required) must not have flash and must be perfectly plain.

4) When IMU dies are set into the threadroller, the markings on both dies must be visible, i.e. facing up. In the case of duplex dies, the markings of both dies will face up or down at the same time.

5) When using re-ground dies, the total width of each die with shims must equal the initial width of the die when new.

6) After setting the dies into the threadroller, it is always better to reduce die squeeze when rolling the very first parts; otherwise, the dies can be damaged.

7) During the rolling operation, die squeeze has to be kept as low as possible, since a slight excess of pressure will reduce die-life.

Check die upper level, as shown here. Place a perfectly straight steel rule on the upper side of both dies. Let the ramslide move idle and make sure that the upper sides of both dies find themselves at the same level during the 3 following moments: 1) at the start of the stroke, when the blank is fed between the dies; 2) halfway through the stroke, when the centres of both dies face each other; 3) at the end of the stroke, when the part is rolled out of the dies.

Check die vertical parallelism, as shown here. Roll a blank after having reduced die squeeze, without forming the thread fully; make sure that the external diameter is constant along the whole threaded length: the rolled part must not be conical.

Check die horizontal parallelism and the correct starting position of the blank. Horizontal parallelism is checked by placing gauges in between the straight parts of both dies, i.e. not taking into consideration die tapers. Distances A and B must be equal. In order to achieve a correct start of the blank, C must be equal to the difference in length of both dies, divided by 2.

Check if the blank is fed correctly. Make sure the rails and the pusher blade are not worn out or warped. The set-up has to be carried out so that the blank is properly placed before the dies by the pusher blade, otherwise, if there is play, it may not start off properly.

Check die set-up, as shown here. After having reduced die squeeze as much as possible, the blank must undergo a little more than half a revolution so that the thread crests of the dies mark the shank. Take the blank out from the dies by retreating the moving die and see if the marks left by the moving die match with those left by the fixed die. In case the matching is wrong, correct it by adjusting the fixed die.

Check presence of laps in the screw thread. Laps, as shown here, are formed when the dies are not properly matched. They can be detected in 2 ways. 1) Hydrochloric acid etching: after having taken all the grease off from the rolled parts, place them in the acid and keep them in for about 5-10 minutes, take them out and dry them using warm air. Then check with the aid of a magnifying glass if laps are to be seen on the thread flanks crosswise to the parts' axis. 2) Metallographic microscope: cut the rolled part lengthwise, form a test sample, polish it and check with the microscope if laps appear (see illustration).