Pro­fes­sor Ham­mer

Last in, first out is al­ways a good ap­proach

Street Rodder - - Contents -

QThanks for shar­ing your ex­pe­ri­ence and knowl­edge with the com­mu­nity. I have been a long­time reader of your col­umn, and your other ar­ti­cles in Clas­sic Trucks and STREET ROD­DER mag­a­zines. I have been work­ing on a ’36 Chevy two-door sedan project, and I’m now work­ing on the body metal and pan­els.

I have a dam­aged front fen­der, and with my lim­ited knowl­edge and ex­pe­ri­ence, I want to limit any fur­ther dam­age I might cause to the fen­der while at­tempt­ing re­pairs. I have at­tached some pho­tos, and hope that you might share your thoughts and any guid­ance on how to ap­proach the re­pair. Ted Chrisos­tomo


A I’m very glad you have en­joyed my con­tri­bu­tions to STREET ROD­DER and Clas­sic Trucks mag­a­zines. It’s a joy for me to help peo­ple.

Re­pair­ing the dents in your fen­der should be pretty straight­for­ward. For­tu­nately, the largest dent ap­pears to have stopped just short of the bead on the fen­der edge, which eases the job con­sid­er­ably. The ba­sic prin­ci­ple for straight­en­ing a dent is

“last in, first out.” If you imag­ine how the large dent was formed, the fen­der ap­par­ently col­lided with some sta­tion­ary ob­ject. When they first touched, there was a sin­gle point of con­tact, but as the ob­ject was pushed deeper and deeper into the fen­der, the dent spread out, be­com­ing wider and deeper.

To take the dent out, it’s best to start from the out­side of the dent and spi­ral in to­ward the cen­ter. Since the fen­der is off the car, it may be eas­ier to work on a bench. Put some sort of pad­ding on the bench, like a stack of tow­els or a mov­ing blan­ket, and po­si­tion the fen­der so the dam­aged area is close to the pad and easy to reach from the in­side. Rather than strik­ing the metal di­rectly with a ham­mer, you will have bet­ter con­trol if you use a wooden tool to move the metal. I of­ten use a wooden 2x2 for this, cut to a con­ve­nient length, per­haps 12 inches long, with one end sanded to a con­tour that matches the crown of the fen­der.

You can po­si­tion a tool like this very ac­cu­rately, and when it’s pre­cisely where you want it, strike it with a ham­mer, us­ing just enough force to make the metal move a lit­tle with each blow. Work gen­tly around the edge of the dent and you will see the perime­ter get smaller and smaller. Keep work­ing in this man­ner un­til the ma­jor­ity of the dent is pushed out.

Now you can turn the fen­der right-side up and con­tinue the smooth­ing with a ham­mer and dolly. Most of your work should be off-dolly, so you don’t over-stretch the metal. I can see there is a small crease at the base of the dent, and this may re­quire some on-dolly work to get out. Since the crease is so small, it’s pos­si­ble that you can get it out with care­ful ham­mer­ing, but if it doesn’t come out com­pletely, or if you see that the metal is start­ing to over-stretch from this ham­mer­ing, you may need to use heat to get the last traces of the crease out.

If heat is re­quired, you’ll need to get all paint and other con­tam­i­nants off the metal, both in­side and out. I would use an oxy-acety­lene torch with a fairly small tip, per­haps a “0” size, and heat an area per­haps 1-inch long to a dull red. This area needs to be ham­mered while it is still hot, and it is very im­por­tant not to hit on-dolly, since hot metal will stretch very eas­ily. Work your way along the crease in this man­ner, un­til all traces of the crease are re­moved.

If you over-stretch any area on a high-crown panel like your fen­der, you may need to use heat shrink­ing to bring it down. Again, you would heat a small area to a dull red color, and ham­mer off-dolly. I do NOT rec­om­mend chill­ing the hot metal in any way be­cause that will harden it. Take your time and let the metal cool nat­u­rally, which will keep the metal nice and workable. Give these tech­niques a shot, and drop me a line if you have fur­ther ques­tions!

✦ This Chevy fen­der has some large dents. This month we’ll re­view some ba­sic tech­niques for re­mov­ing dam­age like this.

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