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Repairing Cracks In Fender Pan

welding cracks sheet metal

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16 replies to this topic

#16 Utah Smitty OFFLINE  

Utah Smitty

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Posted July 06, 2013 - 06:54 AM

 Smitty, once you get all the welding done, buy a needle scaler from HF and peen the heck out of all welds to stress relieve them. And I mean peen them until the ripples are all gone. As the weld cools it shrinks putting stress on the weld and the parent metal alongside it which makes it crack again. The peening stretches the welded area relieving the stress.

                                                    Mike

Thanks, Mike, I hadn't thought of that, but it definitely should be done.

 

Smitty



#17 Utah Smitty OFFLINE  

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Posted July 07, 2013 - 10:06 PM

Well, I got all the welds ground flush on the underside of the pan.  One problem that surfaced with this is that I lost the trace of the crack, though I can see it from the top.  That, and the fact that welding a bead on the cracks on the underside will prevent the support plate from mounting flush led me to decide to put the welds on the top.  The pan metal is so thin that I can't leave a sufficient "V" in the metal itself.

 

PAN PLATE OLD WELDS GROUND.jpg

 

I also decided to use a thicker piece of metal.  The one I chose is approximately 3/32", so it's somewhere around 12 or 14 guage.  It was very rusty on one side, and moderately rusty on the other.  I cleaned up the moderately rusty side--tried a 4" wire wheel in a die grinder--worked well, but time consuming.  I also tried an abrasive flap wheel... worked faster, but not sure if it will last the whole plate. 

 

Then I remembered my 50 year old Milwaukee angle grinder. 

 

The thing is heavy--15 lbs or so, and turns slower than modern grinders, but it gets the job done...

PAN PLATE RUST REMOVE.jpg

 

How to cut out the piece I need--approximately 14.5 x 19. I bought a new combination Plasma Cutter, TiG welder, Stick Welder a couple weeks back, and this let me try it out for the first time.  The machine is Chinese-made, and carries the "Lotos" brand, but it is backed by a 3 year parts and labor warranty, and has a repair center in California.  It cost $738 delivered, but I also had to put a welder-type 250V plug on the end, and ended up making a 20' extension cord to boot. 

 

LOTOS LTPDC2000D FRT.jpg

 

It came with an air regulator, but I had to put a dessicant filter on it as well... it took a little doing 'cause I didn't want to go to the store, but I got it worked out.

 

LOTOS PLASMA REAR.jpg

 

I'm pretty rusty at using a plasma, especially to make a clean cut.  However, after learning to not move the torch head so fast, the cut turned out pretty good.  I did clamp a piece of bed frame angle iron to use as a guide.  The torch head also has a metal standoff that helps to keep a consistent distance from the metal.

 

PLASMA CUT COMPLETE.jpg

 

Anyway, I cut the plate out, then held it against the fender pan and traced some of the holes and the outside edge with a mechanical pencil.  I carefully found the center of one hole, then drilled it... first with a 1/8" bit as a pilot hole, then to 1/2" with a step drill.

 

I then bolted the plate to the pan with a 1/2" bolt.  The holes were right at 1/2" so it was snug, but that was a good thing. I traced the rest of the holes, using a 1/2" washer to trace those that were broken out--I found part of the hole in the metal and traced it, then completed it using the washer.

 

I then drilled the other holes... got everything done except for the 2 mounting holes... I'll finish those up Monday, then start on the mounting holes by the foot rests...

 

PAN PLATE PILOT DRILL.jpg PAN PLATE STEP DRILL.jpg

 

 

The ol' JD420 looks a little forlorn, sitting there without it's pants on... :smilewink:

 

JD420 W_O PAN.jpg

 

More later...

 

Smitty


  • olcowhand said thank you





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