Twisting of double-ended tie rods

April 30, 2005
Q: Do you know a technique for forging a part with sockets or bowls at two ends, with different orientations?

We have a product that has tie rod sockets or bowls on both ends. We plan to forge the part in a fashion similar to what’s used for typical tie rods — with upsetting on both ends followed by the usual trimming. Now the customer wants to have the bowls oriented differently and at a 60° angle, which makes it a difficult forging job. We changed our progression to forge one end, followed by trimming, and then the other end from the upsetter. This is a complicated progression and will reduce our production rate to half, or less, as we had been forging the double-ended part in a simple, three-blow sequence.

Suppose we redevelop the procedure to include the same forging sequence, followed by trimming and a subsequent twisting operation that would require another station in the trim press? This would add the twisting operation but not the extra forging operations. Do you know of any such twisting operation? If so, are there drawings available to show how such a twister is designed?

A: You have a good idea. I do not know of anyone doing the twisting operations on such a small part. Forging separate ends of a longer bar probably would be fine for parts that would permit it. However, the overall length of less than 6 inches fairly rules out that approach.

You could develop a split-clamp arrangement that is spring-loaded, and then place the forging in the nest and start the project by manually twisting the clamp. It would have to rest on bearing-lined trunnions much like those used by diecasters, where the full die can rotate while dumping out the castings from the bottom die. In this case, the spring-loaded clamps would be split in the center of the rod and allow the twist to take place. You might be able to get information from diecasting sources about such an arrangement.

That would be a starting point. You could get a feel for the forces required by placing a torque wrench on the twisting end of the clamp. As you will probably discover the loads will not be great, but to get accurate angularity you will need to develop a stop block of sorts to register the twist angles. Once you have developed the spring-loaded clamps, you can then study ways of duplicating the twisting action in a die set, perhaps with a stabber or cam. Remember, you will probably need to have plugs enter the bowls to prevent their collapse during the twisting operation. This should be a consideration when you design the split clamp that is spring-loaded, top to bottom. As for temperature, it can go as low as 1,400°F and still be soft enough the allow a successful twist.

For more information on twisting devices, contact press sources. Eumuco has excellent experience at manufacturing twisting tools. These are much larger and require a moderately large press with a reasonably long stroke. These can be hydraulic or mechanical press types.

For more than 40 years H. James Henning held key technical positions in the forging industry, including as director of technology for the Forging Industry Association, and as president of Henning Education Services, a Columbus, OH, firm specializing in customized education and training in forging technologies.

Guidelines and recommendations offered in this column are based on information believed to be reliable and are supplied in good faith but without guarantee. Operational conditions that exist in individual plants and facilities vary widely. Users of this information should adapt it, and always exercise independent discretion in establishing plant or facility operating practice.