I am fabricating my downpipe and want to get some advice on making the hole for the 1.5" dumptube at an angle of 45 degrees or less and notching the 1.5" tube. I don't have a drill press or even a tubing notcher. Should I just take this to a local machine shop? I will tig the joints so I need them very tight.

 

If you have an angle grinder just make your notch with that.

 

I would use a hole saw the minimum diameter of the elliptical and complete the long ends with a diegrinder.

 

I just cut the oval hole with a zip wheel on a 4.5" grinder and then clean it up with a carbide burr. You can cope the tube pretty close with the zip wheel too and use a flap wheel or grinding disc to clean it up.

 

You can eyeball this cut pretty easily. First slash cut the tube on the angle you want. When you lay the slash cut against the downpipe, get a sharpie and just draw the curvature on the slash cut 1.5 tube so that it follows the contour of the downpipe.

It's hard to explain, but notching is very easy to eyeball if you just basically draw a curvature line on the pipe to be notched while it's sitting against the tube it'll be mated to. It's easy because the curvature line you draw should be equidistant from the tube your mating it to, so your eye can pick it up easily.

Once drawn you can cut out the majority with a cut off wheel then just do some final grinding to get the shape right. I use the cutoff wheel, then the round end on my belt sander....perfection.

 

Thanks guys. Also, the downpipe and flex joint are all mild steel, the existing dump tube and flange are mild too. The tube I have to complete the merge back into the downpipe is stainless. I have solar flux for these joints mild to stainless joints. Is there any problem having 1/2 of the dump tube mild and the other half stainless?

 

it's fine to have that piece of stainless in there. The solar flux cant hurt either.

 

there isn't as much room as I figured there would be, but I think the entry angle will still be close to 45 degrees. The space between the downpipe and the dump tube flex piece is about 1/4 - 1/2". Cutting the piece to fit in there seems like it will be difficult even with the suggestions given above

 

Sorry, off topic, is that a corrado in the background?

 

it is a slc rado.

good luck that looks like its going to be a bit tricky to fit the last piece of pipe.

 

yup, it is an slc (vr6) corrado back there. The downpipe is for a 16v turbo on a 90 jetta. I started cutting the hole on the downpipe with a dremmel 1" cutoff wheel. The other cutoff I have available is a 4.5" on my angle grinder. Thats too big to use on the downpipe. I'll use the 4.5" to shape the dumptube, but I think the dremmel should be able to cut the hole in less than 30 minutes.

 

You should also look into a small carbide burr for the dremel. Its much easier to shape metal with a burr than with a wheel or stone.

Nice SLC.