TIG thin tubing (mild steel, angle/arm positioning)

admin

Hey everyone,I introduced myself just a bit ago about building a small car in a club (FSAE). I've since started practicing TIG and am getting OK progress, but I need guidance on positioning for tubing.So far I'm doing OK on flat or straight joints, but for tubes I need to constantly change angle and position. I am having a lot of trouble with this and was wondering if you guys have any advice for me? As a reminder, I'm fairly new to TIG - I have the basics studied but this is my biggest problem. I don't have a gas lens yet nor a bigger cup, but I'll get them soon probably.The tubing is usually 1" OD or under, which thicknesses anywhere from 0.030" to 0.065". Here is an example frame to get the idea of what we're working with:
Reply:You have chosen to jump in the deep end with both feet, and it sounds like you can't swim yet. Tig in general takes quite a bit of practice since you have the most control over the puddle. All those little things like torch angle, travel speed arc length, filler manipulation etc, will effect your weld puddle. Out of position welds are even harder and take more practice. Thin material increases the difficulty. Round tube increases the difficulty again, and small thin round tube increases this exponentially. Now you've also tossed complicated tube clusters with restricted access in the mix as well.My suggestion is to back up and start with the basics. Trying to jump to chapter 22 will usually end up in frustration. If you lack the basic skills to do simple out of position welds on flat plate, you will not have good results when you suddenly have to combine those basic skills with constantly altering your torch angle rapidly while working around obstructions in 6G. I tell students who want to learn pipe that they need to get to the point on flat plate where they do all the basics instinctively. If they can't do the basics, then they will have issues when they start doing complicated stuff.I hate to tell you this but you are looking at several hundred hours of practice minimum before you get the basics down well. Taking a class and having an instructor watch you weld will be the fastest route for you to take. I can watch someone weld and quickly make suggestions and corrections to things like body position torch angle and so on that are very difficult to convey by text and still picts. In the average 48 hour night class most tig students are lucky if they get thru beads on flat plate and lap joints and are on to T joints. Students in their 2nd 48 hours of tig are lucky to get thru all the rest of the flat and horizontal joints and possibly start on vertical.Even with all my hours helping students, I'd find 1" thin round tube clusters to be a challenge the 1st few hours since it's not something I do regularly. I'd have to sit and practice quite a bit to get to the point I'd be comfortable. For someone just starting out, this would be very daunting..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:I'll follow your advice and stick with basics. I know I'm jumping way too far ahead of myself, but soon enough I will have to do thin tubing like this. We're short handed and have essentially zero people who can weld proficiently. Since I'm now directing fabrication for the club, I'd like to get as good as possible (and quickly). It's a sticky situation for sure...I contacted the local EAA Chapter and see if they have anyone who is willing to give me some instruction or pointers.
Reply:DSW has a lot of good points but since it sounds like you need to keep moving forward anyway this is what I would suggest. Tack the whole thing together first. At that point start with the easiest welds first. Weld as far around the tube as you feel comfortable depending on reach and visibility. The nice thing about TIG is you don't have cold starts like MIG so multiple starts and stops shouldn't sacrifice strength as long as your heat is right. Move around the whole frame doing a little weld in one area and then one far away from it. Bouncing around like this will help minimize warpage. Starting with the easiest welds should give you time to get more comfortable with the more challenging ones. If this was something that was going to hang on a wall I think the above advice would be plenty good but for a chassis that is going to be on a track at high speeds with a body in it I would definitely try to find someone who can supervise and provide input. I am surprised this isn't provided by the school. I'd hate to think what their liability would look like if this thing crumpled up like a tin can over 100 miles per hour. You might also ask yourself when you are doing each weld how confidant you are that the safety structure will do it's job if it really comes down to it. Post your location. Maybe you can find someone here who would be into helping out. I would bend over backwards to get involved in something like this. Unfortunately there isn't an FSAE team within hours of me if not more so I can be pretty sure you aren't close to me.Lincoln precision TIG 275Millermatic 140 MIG
Reply:I just updated my profile. I'm located in Tucson, AZ, and this FSAE club is at the University of Arizona.I'll ask the President of the club if there's anyone at the school who can give me lessons or supervise (there really should be, as you say). I'm trying to find as much instruction as I can but it's not too easy at the moment (especially with a full-time schedule). I practice about 5 hours a week, which is about the most time I can put in so far.
Reply:Some general thoughts...Definitely take a moment to add your location to your profile at the top of the page. Under profile click on "about me" and then scroll down to "location" and click on the pencil to add your location under the new system. This lets everyone know where you are all the time without having to ask constantly.The comment about tackup is a fairly decent one. You might also think about investing the time in building a rotisserie for the frame so you can position it for easiest welds. Fit up will be critical. You'll make a tough situation even harder if you are also fighting bad fit up and gaps.  Investing in a tubing notcher of some sort would be a worthwhile investment on a project of this type.The EAA is a great idea. If any group regularly deals with tube construction it would be those guys. You might also try some of the local tech schools and see if you can't get some help from their welding students or instructors on this.Practice, practice, practice... post up some of your welds along with all the pertinent settings and sizes and we'll try to give you a few pointers. I usually suggest students attempt to limit their variables as much as possible when starting out. On flat plate that means trying to maintain a consistent travel speed and arc length while simply controlling their amps with the pedal. I do recommend that they do a few beads where they isolate the other variables, say change your travel speed or arc length while maintaining everything else the same, just so you can get an understanding of how these variables change the weld puddle. I frequently see newer students changing two or three things all at once without knowing it. Then they can't understand why they are having issues.... When you get really good, you'll change all three at once, but right now it simply complicates things. Torch angle and arc length are usually the biggie that get guys as soon as they move on to tube pipe. They want to keep welding like they are on flat plate vs constantly adjusting the torch angle to match the weld surface. The smaller the tube, the more rapid the adjustment needs to be..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:When I first started doing tubing joints, I'd just cut small chunks of spare tubing and run lots of joints. Once I got to where I could do a consistent bead, I started cutting them apart to check for penetration. Try to get a good prop and do dry runs. Start at the beginning and trace the joint from where you intend to start and when you intend to finish. Concentrate on keeping a consistent arc length and torch angle (with no actual arc of course).If you can't do it smoothly without binding or discomfort with no arc, you sure as heck can't do it while running a bead, adding filler, and controlling amperage all at once. Practice your filler technique as well. This was actually my biggest weak point when I first started learning. You want to be able to feed filler continuously until you use the entire rod without stopping. Sometimes it helps to carry around an old thick glove that you can double up and lay on the tube you are welding on. Then you can prop your hand/fingers on it. They get hot in a hurry if it's as thin as you say. Depending on the size and orientation of the chassis, you're probably gonna have to get comfortable with welding right-handed, left-handed, on your back, bending over, activating the pedal with your knee, back of your leg, etc, etcIn reality, 80% of the job in doing a chassis like that is FITTING and weld prep. The quality of the weld is directly dependent on fit-up. If the tubing has any kind of mill scale, it's got to go on the joints. Practice practice practice is what it comes down to. Just my two cents from experience..
Reply:I do a lot of dry runs both just before I run a bead and also just while sitting and practicing without striking an arc. Two suggestions I have are don't death grip the torch and don't lock your wrist. You want to be able to roll the torch between your fingers to help with your torch angle. And keeping your wrist loose also helps you follow the contour of the tube. With a locked wrist, I tend to go "straight across" and my arc length changes since I'm not following the tube. Have fun practicing. It will be a ton of fun when things start clicking for you. Oh, and get the gas lens. You'll need some extra stickout to get into those tight angles.Matt A by Zanconato Custom Cycles, on Flickr
Reply:Zank, at one time you had mentioned a beer bottle practice drill that helped one learn to weld thin tubing joints.  Can you describe the beer bottle thing?  Many thanks, Zip.
Reply:Read twice what DSW said , always amazes me where he finds the patience to explain stuff in such nice words.. I would have been more "succinct" .Reality is every single newb want's to master this trade in as few hours as possible on top of that with no help other than internet information and that's just impossible, a few will get almost decent results after a couple of years but not out of position.tip: get a tig finger and torch hand pinky on the pipe, flex head torch and cables will help some, oh and get stubby gas lensquestion:  why round and square tube ? that's going to make fitt-up a challenge even for experienced fabricators--------------------------------------------------------------www.becmotors.nlyup, I quit welding.. joined welder anonymous
Reply:Originally Posted by DonoharmRead twice what DSW said , always amazes me where he finds the patience to explain stuff in such nice words.. I would have been more "succinct" .Reality is every single newb want's to master this trade in as few hours as possible on top of that with no help other than internet information and that's just impossible, a few will get almost decent results after a couple of years but not out of position.tip: get a tig finger and torch hand pinky on the pipe, flex head torch and cables will help some, oh and get stubby gas lensquestion:  why round and square tube ? that's going to make fitt-up a challenge even for experienced fabricators
Reply:That's not the exact frame we're working with, although it's similar. I think on ours it has some square tubing in some parts, maybe to fit some of the components better. I'm not sure though.I really appreciate all your advice guys. I know I'm rushing into this hardcore, but there's not much I can do about it. Some events that took place in the club (alumni graduating, members stopped showing) that put us in a pinch without experienced welders. I will follow DSW's advice and work as much basics as I can first.
Reply:I've been doing a little bit of practice on thin pieces. Here is where I am at currently; looking for some pointers and to correct bad habits. This was thin stuff, I think around 0.040", mild steel. Amperage was set at 42, using a 3/32 electrode and 1/16 filler. I do like pretty looking welds but at the moment I am looking to get the most functional weld, regardless if it's ugly or not.
Reply:if you're not grinding the mill scale off prior to welding you're already off to a bad start.  Needs to be clean clean clean.For 0.040", you "should" be using 0.030-0.035" filler rod, not 1/16".  Try a 1/16" tungsten sharpened to a point about 2-3x the diameter (in other words, long taper).Last edited by Oscar; 09-21-2013 at 05:35 PM. 1st on WeldingWeb to have a scrolling sig! HTP Invertig 400HTP Invertig 221HTP ProPulse 300HTP ProPulse 200 x2HTP ProPulse 220MTSHTP Inverarc 200TLP HTP Microcut 875SC
Reply:Originally Posted by zipzitZank, at one time you had mentioned a beer bottle practice drill that helped one learn to weld thin tubing joints.  Can you describe the beer bottle thing?  Many thanks, Zip.
Reply:Originally Posted by Oscarif you're not grinding the mill scale off prior to welding you're already off to a bad start.  Needs to be clean clean clean.For 0.040", you "should" be using 0.030-0.035" filler rod, not 1/16".  Try a 1/16" tungsten sharpened to a point about 2-3x the diameter (in other words, long taper).
Reply:Wire wheeling tricks you.  You get nice clean shiny MILL SCALE, lol.  Seriously, that's what ends up happening.  It only polishes the mill scale.  Break out the grinding wheel and/or 36grit flap disk.  Only way to go.  You'll thank me later. 1st on WeldingWeb to have a scrolling sig! HTP Invertig 400HTP Invertig 221HTP ProPulse 300HTP ProPulse 200 x2HTP ProPulse 220MTSHTP Inverarc 200TLP HTP Microcut 875SC
Reply:Agreed, you need to sand or grind to remove scale. A wire brush just polishes it. Poor prep leads to poor welds.I'd also agree you need smaller filler. In general you want your filler smaller than your material if possible. It's extremely hard to form a puddle and melt filler larger than the base material and not blow giant holes in things with too much heat. As soon as you stuff the huge filler in the puddle, you chill it and it usually goes away because there isn't enough heat to melt the filler. My guess is you are mostly melting the filler with the arc and not the base material. That would explain the huge fillet with no sign of undercut. It's possible to do this, but you have to be sure you are getting the plates to melt enough and you are getting complete fusion to the root, and not just on the surface. That or you went back over a cold weld to try and make it look pretty.  Fillet should be approximately the size of the base material. It gets a lot harder to keep beads that small as the material decreases, but what looks like 4 to 5  times the size is way too big. As far as smaller tig wire, they do sell tig rods in smaller sizes, but many times guys just use mig wire and straighten it as best as they can..No government ever voluntarily reduces itself in size. Government programs, once launched, never disappear. Actually, a government bureau is the nearest thing to eternal life we'll ever see on this earth! Ronald Reagan
Reply:Originally Posted by DSW  Fillet should be approximately the size of the base material.
Reply:Originally Posted by yoshimitsuspeedWhen you say this I am thinking that one leg of the fillet would be about as long as the thickness of the material is that right?
Reply:I always thought it was the throat that should be as thick as the wall.
Reply:Originally Posted by zankI always thought it was the throat that should be as thick as the wall.
Reply:Thanks for posting that up! It's been a while since I've gone through the handbook. That's a good section on joint design.