I want to start building my exhaust using mandrel u-bends, however sometimes when I make a cut and tack it the joints look square instead of being a nice transition. How can I measure, mark and layout the area I need to cut off so it is nice and smooth?
if you cut the pipe with a chop saw or a cut off wheel with a friction disc it shouldn't bend the pipe. Make sure its at 90* of the part your cutting to make all the pipes the same diameter . I made a set of headers for my plymouth duster and didn't really measure much, i cut a bunch of different curves and tried fitting them in what i thought was the correct spot. Fender well headers and a 3 inch exhaust was a very tight fit but i figured it out! Hope that helps
How can I measure a 90 degree angle at the apex of a bend? I can't use a square is there a wrap around or something I can use? Anyone have tricks?
On curved sections use a thick plastic wire tie.Mark the pipe where the cut needs to be then slip on the plastic tie,pull tight at the cut mark and it will straighten out giving a 'square' cut line around the pipe.Follow the edge of the tie with a marker pen,remove the tie, and you'll have a line around the pipe to cut to. On straight sections of pipe,if you don't have a chop saw,use the above method but using a metal hose clamp. Hope this helps, Mark.
Lay out a circle the same radius as the outside of your bends. Drive a nail into the center point of the circle, and tie a string on the nail. Set your bend inside the circle and lay the string across the tube where you want to cut it. With the string pulled tight, the line of the string will always give you a tangential (straight) cut.
I cut everything about an eighth inch long, try it for fit and mak what needs to be removed. Then I use a stationary 12 inch disc sander to grind the final fit.
It sounds like a good time to invest in a band saw. Then practice. After my roadster was done I had a barrel of s****. I visited a retired machinist who built a Bonneville car. He had THREE barrels of s****. That made me feel much better about my skill levels.
Another version. I mark on the bend where I want the cut, then take a piece of small diameter string and pull it tight over the mark. This will then be a line around the cir***ference that is square to the tube. I then take a can of fast drying black and spray paint the string. Remove the string and you have an unpainted line around the cir***ference that represents where the cut should be.
I use a masking tape or a hose clamp. I cut it long and grind to fit. The more you do the easier it will get. A band saw is the best way but i usually use a sawzall.
<center> <br /><br /> <br /><br /> <br /><br /> <br /><br /> </center>i fabricated the exhaust on my roadster using this fixture and an abrasive wheel in a radial arm saw. a couple of things that you need to keep in mind, cut the wood arbor out of material that is at least half as thick as the diameter of the tubing and make it a friction fit. and keep the kerf to the waste side if the line that you are cutting to. your results may vary. hope this helps.
I use a chop saw and always cut it a little long and grind it to fit using a square and the belt sander. I like the plastic wire tie idea. Practice helps also, I dont know if you noticed after I built the studebaker header, but in my u bend box I have a couple s**** pieces from making cuts on the wrong angle.
I also used a chop saw. I took a piece of plywood, made a circle that fit inside my u bends. Then I drew lines through the circle and across where the tubing would be. Kind of like what hotcoupe did, but his jig is designed better. Worked good for me. I would cut to one side of the line though, then use my little angle grinder with roll lock disc, sand to fit. I ended up with a couple of s**** pieces, but I was happy to do the job myself. It was the first set of headers Ive ever built......but it was fun. Ill see about posting some pics tomorrow, I'm proud of them. This is also how I built my intake.
While a chop saw and jig are way cool... If you are truly bux down... Screw a stainless hose clamp on there as a cutting guide and clamp 'er in a vice and cut it with a hack saw. Crude? Yes.... But the H.A.M.B. prides itself on good work done on the sly.... Hang in there! You'll get it... BTW... My favorite saw blades are the new 'TORCH' blades by Milwaukee for their SawZall... Awesome blades. That's what I would used to cut exhaust tubing if I had to do it freehand... HTIH Jeff
When i built the headers for my coupe i simply marked the section that i wanted to cut off. Cut them in a band saw then smoothed them up with a belt sander, this worked out pretty good. Look at my pics of them they are in my album.
I seem to build headers a lot. I use my large drop arm band saw. I took the base plate and machined the space on both sides of the blade to be exact on both sides. I then simply decide where in the bend I need the cut, Clamp it in and cut it. I never need to square up the cut. Simple and easy, not that building headers is simple or easy. The Wizzard
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