Press Forming Tube for Exhaust Flange

[Twisted Minis]

I got my header flange from Hot Rod Chassis last night and it gave me an idea. I want to use 1.5" tube for my header, because thats what I can bend, and it matches my cones from Cone Engineering. As you can see, it doesn't really fit.



So last night I though I might be able to make a die to press the tube over and force it to take the form I wanted. I found an aluminum square that was close to the size I needed, so I ground it down real quick and tried it with a piece of copper pipe. It made a pretty rough square, and galled the aluminum a bit. But I now know it could work, and it also showed me what kind of space I needed to leave for the tube to form over and provide a good gap.



I found I needed to leave about 3/32" between the die and the inside of the flange for the tube to fit well. So this morning I started building a die out of steel. It needed to be 1 3/16" wide on one side, and 1 5/8" on the other. Not having any large blocks of steel, I cut three pieces of steel 1 5/8" wide at the bottom and 1 1/4" wide at the top. I used two pieces of 1/2" plate and one piece of 3/16".


I cut them larger than I needed, because I'm not that great with the plasma on thicker stuff, and needed them to be smooth. So I got out the 9" grinder and went to town until they where all roughly the same size.


I then welded them together with the 3/16" plate in the center of the two thicker plates.


I then proceeded to grind the blocks until they all matched. Then I raduised the corners to match the die as best I could, and did some finish grinding with a 4.5" grinder and a 120 grit disc.


I made sure it fit inside the flange well, and adjusted it as needed until I was satisfied.


Now time to test it out. I coated it in some low heat lithium grease to help the process, and make it easier to remove.


I then pressed the other side of that same copper pipe onto the die.


The die was easy to remove with a hammer and a brass punch. It left the tube looking like this.


I tested the fit, and I was happy. It fits very snug on the back side of the flange, and left a weldable gap at the front. I think if I press the tube on just a little farther I can tighten the gap at the top so I can TIG weld it.


I didn't have any thin wall steel to test this with, but I wanted to post it any way. Steel gets delivered here next Monday so I will report back when I try it in steel.

[Admin]

Welcome to the site, sweet write up on the die form...

[VLADD]

I like it!!
It's good to see some inginuity!
What's the header for?

[Twisted Minis]

I like it!!
It's good to see some inginuity!
What's the header for?

Its going on an inline Chevy motor.

[VLADD]

Can't wait to see the finished product!

[fabr]

On another site there was mention of welding the head side of the tubes to the flange and on the outside of the flange just using plain brass brazing rod to build up a nice radius of filler. That acts as a "cushion" at the fillet to significantly strengthen this breakage prone area. Are you going to do that?  The brass filler also flows deeply and completely fills the void around the tube where it doesn't perfectly fit on the out side. I've done it on many headers and have found it to work quite well.

[fabr]

If entropy doesn't post them pics up I'll pirate them later to show it better.

[Twisted Minis]

Like I said on the other board, by pressing the die in deeper I can get a tight fit on both sides of the flange. And I will probably just weld both sides. The way some of the tubes have to fit make it complicated. Unless I come up with some solution that doesn't make the header ugly.

I still don't understand why welding ont he outside of the flange is such a bad idea?

[fabr]

IMO only! It's not that welding is bad as much as some feel brazing is better. Why you ask.The feeling is that you are not using as much heat ,the metal is heated just enough to allow the brass to melt and flow.A good deal lower than welding temps are. Second is that the brass is more easily formed into a larger fillet than steel filler and therefore inputs less heat stress into the tube since you can flow large amounts of filler in a short time. The larger fillet transfers stresses out over a larger area along the tube. All of these things and I'm sure others make for a more durable header in severe conditions.

[Twisted Minis]

But if the fit up is tight on both sides? Is it okay to weld then? A lot of the headers I have bought are welded on both sides, or only one one and nothing on the outside. I've never seen one brazed.

And how severe of conditions will a street driven hot rod really see?

I'm not doubting the process, I just don't fully understand it. And I don't necessarily like the idea for my application because of the way some pieces need to be made.

[fabr]

It's an improvement but for what you are doing you will likely be fine welding both sides.Try to not overheat the tubes when welding. This was just a discussion of different practices.You won't likely see many headers brazed on the outside either.I've done it both ways but longest lasting was brazed.

[Twisted Minis]

Took a while for me to remember to take a picture, but I did it in steel with pretty good results.

[WelderPat]

 First off excelent job on the press forming.Make sure you keep that die put away somewhere it may come in handy again some day.
 If you tig the inside with the tube shy of the inside of the flange by about a sixteenth of an inch.Then fillet the outside with either brass or silicon bronze (I personaly prefer the bronze) the header will last forever.
 When you do the outside if you bolt it to a head it will flaten it out nicely.
 If the end of the tube is not paralell to the flange where you weld it push it just through and knock it down with a grinder.
 The engine vibration.exhaust pulses,temperature changes,and the weight of the header hanging there make these some very high stressed welds.

[Admin]

First off excelent job on the press forming.Make sure you keep that die put away somewhere it may come in handy again some day.
 If you tig the inside with the tube shy of the inside of the flange by about a sixteenth of an inch.Then fillet the outside with either brass or silicon bronze (I personaly prefer the bronze) the header will last forever.
 When you do the outside if you bolt it to a head it will flaten it out nicely.
 If the end of the tube is not paralell to the flange where you weld it push it just through and knock it down with a grinder.
 The engine vibration.exhaust pulses,temperature changes,and the weight of the header hanging there make these some very high stressed welds.

welcome Welderpat, great advice to BTW...

[Punkur67]

A question about the brass or bronze welding. A neighbor brought over a streetbike exhaust last night with a crack in one of the welds. The welds apear to be either brass or bronze. The header is chromed. Can I clean the weld and run it over with my tig or is this a torch only process? I want to try and save as much chrome a possible and think the torch will ruin more that the tig will. And I also am set up for tig at the house and not a torch? Any input?