Manipulating metal GETTING TO GRIPS WITH THE LATEST TECHNIQUES IN STRAIGHTENING METAL ON TODAY’S VEHICLES, FOCUSING ON COSMETIC REPAIRS TO OUTER BODY PANELS
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t should come as no surprise that the best techniques for straightening today’s high-tensile metals are very different from those used in days past. Not that long ago nearly all vehicle bodies were made of mild steel throughout. You’d see some aluminium, but the vast majority were mild cold-rolled steel so a ‘one-size-fits-all’ approach was common. Today there are several different types of steel being used and widespread implementation of aluminum (also in varying grades), so the topic of straightening structure is a whole different conversation. Steel is still the more popular choice and has been prevalent since the inception of massproduced vehicles. However, the type of steel used has changed recently and the repair process and even the ability to repair it at all has changed with it. So the first thing to know before considering straightening metal is what type of metal it is and whether it can be
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Auto Channel Issue #41 November 2021
safely repaired. If repairs are allowed, there may be guidelines as to what are acceptable practices. A couple of the early techniques are still in use today. The hammer and dolly method may still be a recommended practice by the manufacturer if there is backside access. Another, newer technique would be that of glue pulling, a technique covered earlier in this magazine. There have been incredible advancements in the training and tools used for glue pulling repair as of late. Like any process, training and practice go a long way to ensure success! Some vehicle manufacturers provide guidelines for the straightening of metal. As noted earlier, we are focusing on outer body panels. FCA has a guideline published for Chrysler and associated brands that reads as follows: FCA US LLC Service Engineering’s position on the use of heat during collision repair is as follows: • Any damaged body panel or frame component, which is to be repaired, must be repaired using the “cold straightening” method. No heat may be used during the straightening process. • During rough straightening prior to replacement, damaged panels or frame components may be heated to assist in body/frame realignment. This application of heat, if absolutely necessary, must be constrained to the parts which will be replaced and not allowed to affect any other components. This “no heat” recommendation
is due to the extensive use of high-strength and advanced high-strength steels in FCA US LLC vehicles. High-strength materials can be substantially and negatively affected from heat input which will not be obviously known to the repairer or consumer. Additionally, application of heat will alter or destroy material coatings utilized for corrosion protection and which may not be restore-able.
The hammer and dolly method may still be a recommended practice by the manufacturer if there is backside access Ignoring these recommendations may lead to serious compromises in the ability to protect occupants in a future collision event, reduce the engineered qualities and attributes, or decrease the durability and reliability of the vehicle. This statement supersedes any previously released information by FCA US LLC. One must use common sense when applying these guidelines. I think that they are okay with the use of ‘heat’ when using the glue pulling repair method as the recommended panel temperature of around 26 degrees is the generally accepted temperature. The use of a heat gun to bring a panel to that temperature would be acceptable. Obviously, panel temperature can reach well above those ranges in various climates around the world. Some manufactures may set an outline for making repairs to outer sheet metal using a welded washer or welded stud pin method, such as this example
