Tube chassis question

Didn't want to hijack anyone else's thread, but had a question on how you notch tubing the right way, correct angle etc.

Just don't want to get into the situation where I "Cut it twice and it's still too short"

I see all kinds of obtuse angle in the tubing and how do you go about detemining this?

I probably opened a can of worms now!

I use a digital angle finder and just do some simple math comparing angles from the bars. and I use the following tool with a cordless dewalt drill and a cordless milwaukee angle grinder to notch.

X2 on the digital angle finder because it's amazing how far off some of the cheap bob-weight/pointer angle finders from Homedepot/Lowes/etc can be. Sometimes it almost gets comical when working with a bob-weight/pointer angle finder. You place it on the tubing & wait forever for the weighted pointer to stop swinging back & forth. Then you 'thump" it a few times to help it set on an angle. But with every thump it lands on a slightly different number. "Thump", 25 degrees......"Thump", 24 1/2 degrees......."Thump", 25 1/4 degrees........"Thump", 26 degrees. But the digital angle finders, very stable & repeatable (even the cheap ones). Place it on the tube repeatedly and BINGO.....24.70 degrees every time.

I never have liked any of the holesaw notchers because they do have a limit on the max angle you can notch. I just notch/fish mouth tubing the old school way, 14" chop saw to rough cut the notch, 8" bench grinder to finish the notch, belt sander to smooth any sharp edges & put a decent 45* edge for heat penetration on thicker wall tubing. Other tools I use associated with fitting a piece of tubing are an orbital sander, sandpaper, & Scotchbrite to remove any outer surface scale at the weld joint. And of course a drill & 1/16" bit to drill at least one pressure relief hole in each section of tubing.

As for using cordless tools in the shop, I gave up on them long ago. Too much of a hassle trying to keep at least one battery charged in reserve. And when a battery takes a siht, the replacement batteries cost too much. Cordless tools are fine for keeping in the trailer's tool box & use at the track. But they suck for every day repeated heavy shop use.

I agree!!!

whatbumper you must be crazy quick, patient or just down right good to do that work with rechargeable tools!!

jones wrote:I agree!!!

whatbumper you must be crazy quick, patient or just down right good to do that work with rechargeable tools!!

Milwaukee tools are the best I have found.(A set of power tools came with a new Chevy pickup that my uncle bought) I got tired of tripping over the damn cords all the time. As long as you keep an extra battery on the charger it is not that bad. We've built a couple 25.5 fox mustangs this way and each time it gets easier. I don't work by myself. One cuts and notches with the tubing notcher and the the other finishes the notches with the grinder.

I do have a cord on my chop saw though.

This is NOT a perfect system. The other person is my brother and we exchange our share of curse words but I wouldn't want to work with anyone else. His vision and ability to problem solve are second to none. He has to being a full-time farmer that takes care of over ten thousand acres in a thress man operation.

Thanks for all the input- I eventually want to rebuild my chassis, it's currently a 2x3 w/~.078 wall frame, ladder bar suspension, the cage is 1.75 x .125 wall that was stick welded back in the late 80s when that tubing was legal, or at least that's what I thought. I know stick welding is a no no, so I purchased a good 220v, 180 amp mig welder and am going to set that up to practice on some tubing. I used a friends similar welder and was amazed at how easy it is to lay down a decent bead, as long as you have the machine set up right.

Future plans are to get a tubing bender, but not sure what shoes to get. I know I'll need one for the 1 5/8 tubing , but not sure what radius bend is best. Any other sizes to get as a suggestion?

I did find this site for using a tubing bender and how to bend tubing

http://www.therangerstation.com/tech_library/pdf_documents/bendinginstructions.pdf

I like the idea of using the digital angle finder that sure sounds like it makes the job faster and precise.

I have a drill press w/tilt table/degree pointer, but need some ideas for a tubing fixture on the table.

Looks like there's going to be a lot more research before I can get started.

Ultimately, I think I'll wind up just cutting everthing out and starting over with a round tube, modern design chassis.

Get ready to spend the $$!!

Nothing wrong with stick welding as long as you know how to weld! I know a lot of welders that can lay down a stronger, prettier weld with a cracker jack box than the best mig.

jones wrote:Nothing wrong with stick welding as long as you know how to weld! I know a lot of welders that can lay down a stronger, prettier weld with a cracker jack box than the best mig.

I agree, the guy that welded my chassis back then was a talented buzzbox welder. I don't think stick welding will pass chassis cert though, is this correct?

I have an old craftsman Ac/DC welder that I bought at a garage sale for $50.00, but can't make a good weld with it, too much slag inclusion with a 7018, 6010, or 6011. Someone once told me the welder may have a bad rectifier, whio knows?

I like to think its the machine and not the operator!

Our welders use sticks and alot of their welds have to pass x-ray. I see no reason how or why a good weld wouldn't pass tech. (Not cracker jack boxes though)

I think it has more to do with the operator than the machine. I could be wrong, I'm not 100% on SFI, NHRA and IHRA spec's.

Edit: I am probably wrong so just ignore me. The small size of chassis tubing might be hard to control heat in.

Josh I think I remember the rule book saying you can use a mig or tig no stick....
Dave will respond when he see's this I am sure....


Randy

the Coug wrote:Josh I think I remember the rule book saying you can use a mig or tig no stick....
Dave will respond when he see's this I am sure....


Randy

Thats is right Randy mig/tig only It has to do with a few things heat in the tube and contaminates in the weld pubdle.

after going TIG I will not use anything else on cages. once you get past the PITA attitude (I know I had it bad when I started) TIG is not that bad but of course all my stuff is CM. MIG is pretty useful though and on a MS cage it is pretty easy. In MIG welding the metal does not have to be as clean as TIG.

Yea, stick & Ox/Acc gas welding is a no-no for NHRA/IHRA/SFI stuff. Wire welding mild steel is fine (if done correctly) if that is what you have to work with & don't have access to a Tig. Use only solid Mig wire & gas (no flux core wire).

One mistake that some people make when fitting mild steel tubing for Mig welding is they actually fit the joint too tight (especially the .134" wall stuff) making it much harder to get the proper weld heat penetration with the Mig. An ultra super tight fitting weld joint is really only necessary when Tig welding .058" or .065" wall 'moly tubing. The .083" wall 'moly is also fit on the tight side, but with a slight 45* chamfer on the edge. With the .134" wall ms stuff & Mig welding you either fit the tubes touching each other at the joint, but with a decent sized 45* chamfered edge. Or you don't use any chamfer on the edge, but leave an air gap at the joint.

Proper tack weld placement also plays a part in Mig welding penetration & effects the weld joint strength. Before you grab the Mig & go crazy tack welding a fitted joint, look at the joint for a second. Figure out ahead of time how many start/stop passes it will take to go all the way around the tube & which direction each start/stop pass will go. Since Mig welding is so damn cold at the start of the pass, the idea is to place a tack weld where the weld pass will end/finish....and never (if possible) at the start of a pass. This helps "burn" the tack into the puddle because everything is up to full temp by the end of the pass. Starting a weld pass right on top of a tack weld further increases the chance of a "cold" puddle start & less weld heat penetration.

The same weld pass starting/stopping placement idea applies to beginning a new Mig weld pass in reference to previous weld passes. You want to end a new pass stopping at/on an older pass. But (again if possible) you try to avoid starting a new pass at/on an older pass (the "cold" start thinking again).

Tack welds are also a great "oops" fixer if you happen fit part of a weld joint way too loose leaving a gap too big in the weld joint. Just place a tack or two "in" the weld joint gap (vs "on" the weld joint). The tack(s) in the too loose joint will act as extra filler material & cool the weld puddle slightly as you pass over it helping to avoid a burn through.