Cutting tube square in tough places

So, i need to splice in a repair on a non structural piece of roll cage tubing. (Bottom most tube in a nascar style door bar)

Im having a devil of a time cutting this stuff square on the bench, let alone where it runs close to other stuff in the car. 

Can i use an exhaust chain cutter? Any other ideas? Cant get a portaband in there, or 4 inch grinder. So sawzall, hacksaw, gnaw through it in multiple cuts with the plasma that hates anything thicker than 1/8 and doesn't do that well?

Ill take whatever ideas you got. I can do the replacement tube square on the chop saw.

In reply to Dusterbd13-michael :

pix of problem tube joint?

I'm assuming the piece you are putting in will be bench notched/cut and not somehow also cut in the car?

If so just whack it off with a Sawzall as close to square as you can get then match the angles on the bench.  Treat it like any other irregular tube end joint and just make the joined tube match what's their with minimal gaps and appropriate weld preparations for the type of weld the joint needs.  

the bottom door bar tube, where the vertical jack point it attached has a hole ripped in it on both sides where the jack points were ripped off multiple times. I want to replace the majority of the horizontal center tube. 

Nocones: overthinking it again, aren't i?

I came here to say what nocones did

not gonna lie, i read "cutting tube square" as "cutting square tube".

i'd put two hose clamps around the tube, spaced one sawzall blade width apart, as cut guides.

In reply to Dusterbd13-michael :

Yes probably.  Do it at an intentionally severe angle and you can claim it's for increased weld area.  Which in reality is a real thing that's better.  Something like a 30-45⁰ angle is better then an unsleeved butt joint.  It's probably not an advantage for a sleeved joint but a double ended sleeved joint is really difficult to do because you have to slide the sleeves in after the tube is inserted and for a non structural non spec required cage tube is probably not necessary.  

Also talking about tube frame race cars sure is full of enuendo..

Awesome!

These are the tips i needed!

Angry: genius idea. Hadn't thought about that!

Nocones and Patrick: got it. Ill see how big an angle i can cut in consistently. Have a feeling theres going to be a solid day of work to fix these two tubes....

There are times that I have used a sharpie and a plumbing tubing cutter to scribe a square line around a tube and then a hacksaw/angle grinder/sawzall to make the cut.  Sometimes a hose clamp or even a rolled up piece of paper and a sharpie to mark a square line and then cut.  If using a hacksaw I hope the tubing is mild steel and not cro-mo, because you'll be there a while.  

AngryCorvair (Forum Supporter) said:

not gonna lie, i read "cutting tube square" as "cutting square tube".

i'd put two hose clamps around the tube, spaced one sawzall blade width apart, as cut guides.

This works, but not so well with the cheap gearclamps. Get the more robust bandclamp style and it will do a better job of keeping the cutting implement in the grove. Downside is that they are expensive.

If the jack point design has failed multiple time, why not leave the tube in there and add to it to make it better? If its 1.5" tubing you could rip a piece of 1.75 tubing in half to wrap around it. Or just add material to the bottom to spread the load.

In reply to NOHOME :

I've only tried the cheap worm clamps, but without good success. I've found, if we'll marked, I can do better freehand. But as was said, cut it how ya can, and match the new piece... had not thought of the intentional angle - I like that!

In reply to jgrewe :

I thought about that. But the underlying tube is still compromised. And im not sure where the bew jackponts will land once its closer to done, so im holding off on adding anything yet other than fresh steel. 

Any tips for making the intentionally angled pieces easy on myself? 

Cutting severe angles into the ends of tubes can be a double edged sword. More weld area, good. More heat in the tubes, potential bad. More linear inches of weld to finish down, unfun. Telling everyone you did it on purpose, ego boost! Achieving even gap for butt weld with backer, complicated.

Hack out the damaged areas however you can, and then you will magically have room for the 4" grinder with a sanding disc to square the cut end.

If you are keeping that door bar layout(sounds like you are), I would not do this repair without sleeving the tubes. Door bars are for impact protection, this is no place for potentially weak repairs.

6" sleeve per joint, 3" each side of the seam. Don't forget to rosette the sleeves in place

Bicycle chain wrapped around to be used for a cutting guide. 

Came to suggest using a hose clamp as a guide to mark the tube.

When I cut exhaust tubing in the middle of a curve, I use a hair band (ponytail tie) to find the cross section, and mark it with a sharpie.

If the new jack point(s) are in the middle of that span like the old one, put a bar above it to help put the force into the tube above as well.   Ideally, you'd make a V with the tops of the angled tubes at a node and the bottom at the Jack point. 

I would cut the section out, get it pretty square with a grinder and cut a section of tubing a hair long and hand fit it as close as I could. Chamfer those ends. Then I would cut a couple pieces of tubing that fit inside about 6" long. Drill some holes to do some rosette welds on both sides of the seams.

Slide the pieces inside tube and hold it in place while you wiggle the tubes inside into place using the rosette weld holes. Weld it all up.

jfryjfry said:

If the new jack point(s) are in the middle of that span like the old one, put a bar above it to help put the force into the tube above as well.   Ideally, you'd make a V with the tops of the angled tubes at a node and the bottom at the Jack point. 

This is legit. Also, if you aren't doing hot pit stops on a clock, that jacking point becomes less relevant and could probably be left off completely as long as there is sufficient access to the main chassis rail at ride height with the body on.

Alternatively, build the new jack point off the main rail and triangulate to the nodes of the door bars instead of loading the middle of a span.

So, dumb question:

Which is safer/stronger/better:

1. Grind existing door bars down to clean metal,  then cap the bottom of the middle section with a full length piece of half tube, covering the damage and reinforcing the structure.  Welds would be horizontal the whole length of the tube. And it would be like half armor plate. 

2. Cut and weld like weve been discussing, on angle or with slugs and rosettes. 

A picture of the actual damage would help, that 60mph drive-by pic does not show the damage.

I would look at not replacing the tube, maybe form a patch to cover and re-enforce the area.

Plasma cutter and a hand grinder otherwise.

If you are having trouble with this you have a very long row to hoe....

In reply to bentwrench :

I'll grab one tonight. Of each tube! Im suprised that in 1300 pictures on my phone, i don't have one.

My debate, until the strength of repaired tube was brought up, was how best to approach the cuts for a better repair. I have a very low historical success rate with cutting square freehand. 

Ive gotten some GREAT tips to ghat effect here, and honestly learned some new stuff. 

Sorry. Last night got nuts. 

passengers mess

drivers less bad

The simple way would be to clean it up, cover it with a section of split tubing. Its the bottom bar of a 4 bar basket, probably well below the level where a car will hit you in the side. If you are worried about the strength of that tube add a couple more vertical supports or  fill the holes above and below with some 1/8th plate.

I would put more thought into making the jack point work without tearing off and that extra material will do 2 jobs.