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  1. #1
    febikes
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    Best practice for TIG on bicycle tubing

    Miller has some information about welding on 4130 tubing.
    http://www.millerwelds.com/resources...me-Moly-Tubing

    How much of this applies to bicycle tubing? In what ways are steel bicycle tubings different from plain old 4130?

    There is some other information about 4130 at welding tricks and tips but as expected it is not specific to bicycle tubing.

    For example, do people use the same filler rod for all the various bicycle tubings and if so what rod material and/or size. Also, is the TIG machine setup the same for bicycle tubings as it is for 4130 or are there adjustments to make. ( i am starting out with a Hobart TigMate so really the machine I am using does not have a lot of room for adjustments.

    Other then mineral spirits and acetone, what solvents are people using after sanding and scotch bright?

    I will have some sample tubing scrap soon but I am sure not enough time exists for pointless trial and error.

  2. #2
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    It's pretty much 4130.

    Bike tubing, at least the non-stainless stuff, is mostly pretty much 4130.

    In general, that's a good article about basic welder setup. Many bike builders use ER70, many also use Weld-Mold 880t (good for joining dissimilar materials like stainless dropouts as well as standard mitered joints in 4130). ER70 will be available at any welding shop, 880t is pricier and harder to find.

    You will need to practice and mess with your settings until you find what you like. And after enough practice, the settings you prefer may change. It's more about the skill of the welder than the settings on the box.

    BTW, acetone is nasty and bad for you. Use denatured alcohol or just simple green/water after mechanically cleaning. That's plenty clean enough for steel.

    -Walt



    Quote Originally Posted by markfarnsworth
    Miller has some information about welding on 4130 tubing.
    http://www.millerwelds.com/resources...me-Moly-Tubing

    How much of this applies to bicycle tubing? In what ways are steel bicycle tubings different from plain old 4130?

    There is some other information about 4130 at welding tricks and tips but as expected it is not specific to bicycle tubing.

    For example, do people use the same filler rod for all the various bicycle tubings and if so what rod material and/or size. Also, is the TIG machine setup the same for bicycle tubings as it is for 4130 or are there adjustments to make. ( i am starting out with a Hobart TigMate so really the machine I am using does not have a lot of room for adjustments.

    Other then mineral spirits and acetone, what solvents are people using after sanding and scotch bright?

    I will have some sample tubing scrap soon but I am sure not enough time exists for pointless trial and error.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.com/blog/
    instagram.com/waltworks/

  3. #3
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    'nuff said...

    Drew
    occasional cyclist

  4. #4
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    Thanks!

    I am glad to know that acetone is not required. One thing I like about TIG is that while I am just getting started the process seems really clean. I like that the air quality in the shop is good and avoiding harsh chemicals is a good thing as well.

    I ordered some TIG FILLER ER70S-2 .035 and some 2% Ceriated TIG TUNGSTEN 1/16in.

    I am going to work on my technique a bit to make sure that I start with a focus on quality because no amount of practicing bad habits is going to help me on this road.

    In addition I have decided that one of the first things I will be building before actually going forward with a frame project is going to be a fixture for testing some simple joints. I am thinking about a simple design for testing a "H" weld with three tubes joined together into an "H" shape. A fixture can hold by passing solid rods through each of the vertical tubes in the "H". I plan to setup the fixture with a bottle jack so I can pull apart the welds and/or break the tubing. This will give me a way to measure my welding results as it hopefully improves and as I play with different techniques.

  5. #5
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    As far as cleaning, I dont use solvents.

    I use:

    an angle grinder with a flap wheel to miter tubes and clean scale from dropouts (worn/older flap wheels remove material slower which is good. A lower rpm grinder is good too)

    A drill with a medium wire brush (that doesnt score too much) to remove scale, rust and coating.

    A dremel with a slightly worn sanding barrel thing to remove the inside coating/scale before welding. (The inside weld area of the tubes need to clean of scale/black coating) Tiny steel dremel brushes are necessary for tight corners...

    A tip for strong welds:

    If I am welding .049 or larger, I always put a bit of chamfer, or "land" as I think its referred to, on the mitered edge. Not a sharp edge, but enough that the tube gets better penetration... For .035" its not as necessary or even possible. A little chamfer at the dopout weld areas helps too in many situations

    Most tungsten electrodes are radioactive, and can supposedly cause lung cancer if you dont keep a clean shop!

  6. #6
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    Quote Originally Posted by mattty
    As far as cleaning, I dont use solvents.

    I use:
    That is good advice. I will add this though. First, most tungsten nowadays is not radioactive. Only Thoriated tungsten is radioactive and the other types, cerated, lathanated, Zirconiated
    are not radioactive. Although I would still recommend not taking a big inhalation of the dust if you can help it.

    For truly clean pieces you need not only mechanical cleaning but chemical cleaning as well. This can be done in many different ways and you can use relatively harmless things like alcohol or even soap and water or a ultrasonic. Try this as a test. Clean your item as you are, then get a clean wipe and wipe with alchohol. There will be dirt all over your wipe and this contaminates welds to some degree.

    How clean do we need it? Well, obviously many good welds have been done on what would be considered dirty metal in high end welding situations but alcohol (or simple green as Walt recommended is safe and I feel better and get better results with a mechanical and wipe afterwards.

    Your cleaning methods are great. I do much of the same thing but I have some fancy assed stuff (like a really nice belt grinder). The sound of dremels and grinders drives me up the wall....

  7. #7
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    I don't put much stock in the 'failure test' for TIG. Even a terrible weld is unlikely to break, so please don't rely on that. Poor welds will cause fatigue to happen more quickly, and a simple bench test isn't going to show you that.

    Definitely cut through your test welds to look at the penetration. Make adjustments to your settings and technique and try again.

    And by the time your welds are smooth and consistent, you're all but guaranteed to be making safe welds. And be sure to get feedback from expert welders because I'd trust them far more than I would a good 'test' result.

  8. #8
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    Thanks!

    BTW; great welds and great design. In my book ByStickel welds are second to none.


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    Not true, but thanks. (I only show the ones where I managed to not screw up.)

  10. #10
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    D.F.L. what do you use to hold your seatstays on the lathe while you mitre them?

  11. #11
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    Quote Originally Posted by Carrot
    D.F.L. what do you use to hold your seatstays on the lathe while you mitre them?
    Simple homemade aluminum plate held with a machining attachment, but you can fab almost anything to hold a plate with the cross-slide. I wouldn't seek out a machining attachment specifically for this, I just happened to have them.

  12. #12
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    I did some welding practice this week. The following is the best result I have had so far. I don't really have access to any welding experts for in person advice so please let me know what you see and if possible give me some tips for improvement.


    More photos here:
    http://febikes.wordpress.com/2011/01...ding-practice/

    I was using a very simple Hobart Econo TIG machine (no pulse available on the machine). I had 1/16th ER70 filler rod and was moving the puddle into the filler rod in addition to sometimes pushing the rod into the puddle.

    My what should I be looking for in weld inspection and what sort of inspection checklist should I have?

    Thanks in advance.

  13. #13
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    1. there seems to be quite a bit of scale on there. If you havnt already, try pushing your CFH up to around 30 and your post flow up to 7-10 seconds (and keep the torch there while the argon is shielding it) This scale might also be attributed to too small of a cup size, having the electrode too far out, having the torch at a funny angle(which doesnt shield the puddle properly) Also, if you havnt already consider a backpurge setup that shields the back of the weld too

    2. those little volcanoes are a result of letting of the gas pedal too quickly, try feathering off the pedal

    3. try going in one direction. My rule of thumb is "U" forward. The puddle forms a little U shape where the open part of the U is the direction the puddle moves

    4. Almost always make a puddle and add filler to the puddle at an intermittent interval. (If you've burnt a little hole sometimes you have to shove the filler in there fast at a lower temp to keep from burning more)

    5 Use a welding sequence. Dont weld all the way around at once, you will over heat the thing and cause distortion.

  14. #14
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    More practice

    -Looks like things are getting too hot, or you're not getting shielding gas on the weld when it's still hot enough to react with the atmosphere. You may need to use less heat/move quicker, or work more on getting gas where it needs to go. Or both.
    -Make sure things are clean before you start (hard to tell from these pics, but it's worth saying again).
    -Get a gas lens for your torch if you don't already have one. Remember that more argon is not necessarily better - if you are pushing it too fast, you'll just generate turbulence that will suck atmosphere into the area you want shielded.
    -Play with your settings. A lot.
    -Learn to dab your rod into the puddle (sometimes you'll just run over it too, as you're doing, but it's good to be able to do both).

    Ideally you want fairly bright/shiny rainbow colored metal on the weld bead, not dark black/grey stuff (this slag is what you get when the steel encounters oxygen when it's still hot).

    Let me be clear, though, you are doing awesome. Those look way better than the first welds I did on bike tubing, that's for sure.

    -Walt

    Quote Originally Posted by markfarnsworth
    I did some welding practice this week. The following is the best result I have had so far. I don't really have access to any welding experts for in person advice so please let me know what you see and if possible give me some tips for improvement.


    More photos here:
    http://febikes.wordpress.com/2011/01...ding-practice/

    I was using a very simple Hobart Econo TIG machine (no pulse available on the machine). I had 1/16th ER70 filler rod and was moving the puddle into the filler rod in addition to sometimes pushing the rod into the puddle.

    My what should I be looking for in weld inspection and what sort of inspection checklist should I have?

    Thanks in advance.
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.com/blog/
    instagram.com/waltworks/

  15. #15
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    Thanks!

    I will be getting a gas lens for the torch. Steve at BREW was a big fan of gas lens but I have not gotten one yet. The shop equipment is at a shared techshop but I am sure they will not mind if I buy my own gas lens and bring it with me.

    In terms of movement I think going faster might be the key. I found that I was often spending a lot of time on an area and not moving smoothly. Next time I can hopefully get the heat up quicker and then move along at a more steady pace plus feather the pedal when I stop.

    The Econo TIG does not have much in terms of settings. I can't adjust pre or post flow and there is no pulse. It seems to be a very basic unit with simple amp adjustment (i was set at 30 on the dial).

    When I get a TIG for my shop it will likely be a Miller but I feel the need to do some more practice before making a big buy.

  16. #16
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    I understand that you can run the tungsten out further with a gas lense, but how far out from the gas lense cup is ideal?
    May the air be filled with tires!

  17. #17
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    +1 on what Walt said.

    It needs to be clean, inside AND out. If you have a heater/fan running, direct it somewhere else. Even a minor current will cause the argon to do weird things. Don't forget to breathe and relax when holding the torch. You shake less when your hand is relaxed.

    AND

    It may be your welding device.

    I had an Econotig for a little while. Welding .035 tubing was VERY difficult, as it's 'base' power was pretty hot and it didn't have much(read any) control down low. You don't need a pulse unit, you have a foot that can do more or less the same thing. A pulse will help you find a rhythm, but not make a nicer weld. Of course, it can be used to control the heat if set up properly, but it's not necessary. I have a pulse unit, and unless I was/am doing high production work (welding say, 100 turbo down pipes, in a jig, in a day) I never used it.

    On the EconoTig, Try using some smaller tungsten. I think the smallest I found was .040, which is very small, but it helped with the heat a bit. I made some acceptable welds in .035 stainless and titanium, but I had to move fast. I'd say, for learning. to weld use a .049 or .065 tubing.
    This way, you learn to see what a good bead looks and 'feels' like, after that the thinner stuff gets easier as you can move faster and think about what you are doing less.


    *edit*
    I have a Dynasty 200dx. Had it about 7ish years now, not a lick of problems. My only regret is not buying the 300dx when the prices were reasonable. I have use for the extra juice at least 10 times per year. (never bicycle related)

  18. #18
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    Quote Originally Posted by Brad Bedell
    I had an Econotig for a little while. Welding .035 tubing was VERY difficult, as it's 'base' power was pretty hot

    ...

    I have a Dynasty 200dx (now)
    Haha. I have had the exact same equip. I don't see how you're going to do thin stuff w/ an Econotig. It only goes down to 20A. I never could do thin sheet w/ it but it'll knock out race car roll cages from 0.095" tubing all day long The Dynasty makes doing thin stuff so easy you feel like you're cheating.

  19. #19
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    Dunno if this will help with the minimum-amperage issue, but I found that the non-radioactive tungsten required higher amperage to get the same result. This may help by artificially lowering your machine's output. Anybody else notice this?

    You're doing great. The overheating is a common issue when folks are starting out. Once you gain more comfort and experience, you'll use less pedal and will move more quickly.

  20. #20
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    Quote Originally Posted by D.F.L.
    Dunno if this will help with the minimum-amperage issue, but I found that the non-radioactive tungsten required higher amperage to get the same result. This may help by artificially lowering your machine's output. Anybody else notice this?
    Hey Steve,

    I noticed this too when using ceriated tungsten. Got to step on the gas harder vs thoriated. I also think it's not as bright and it's harder to see under the hood.
    Erik Rolf
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  21. #21
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    The following is more practice that I did last night. This time I used 2% Ceriated 1/16in. The welder is actually a HOBART TIGMATE (not econotig). From the spec it sounds like minimum power is 20 amps and that is what I was using.



    You can click the photo above for a larger photo with more detail and/or use the following links for other recent examples.
    http://febikes.wordpress.com/2011/01/28/more-practice/

    With this attempt I spent more time with prep work. The miter was done on a grinding wheel but gaps were minimal. I cleaned the tubes with mineral spirits, wiped dry, and then used some scotch bright. I don't have emery cloth or files yet so this was the best prep I could do.

    I am using scrap tubing from Evil and Walt (big thanks for sending the scrap). The tubing here is .8mm.

    My short term shopping list includes getting some emery cloth and some good files. For the next attempt I plan to miter with grinding wheel, finish with files, and then clean with emery cloth and then simple green.

  22. #22
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    I'd recommend an amp setting always slightly above what your material can handle. This will give you reserve current when the material's heat sink is good and will prevent you from needing to linger in an area as your 20amps slowly heat up a thicker section to melting temp. You want to be able to modulate the pedal, rather than have it functioning as an on/off switch.

    While your weld has a lot of scale from excess heat, the beads actually look a little cold and lumpy. I'd guess that your amps were too low (I'll typically use 35-ish) and that you spent too much time trying to get the filler to flow.

    I just think you need practice time.

  23. #23
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    What you are doing and the way you are going about it is fun and inquisitive. Its pretty much the same way we went about it when we started. The very first time we fired up the welder, was preceded by some Google searches on "how to weld". In fact the guy that sold us the welder commented, "ehh its not too hard, there are about 3 things you never want to do. Outside of that its no big deal." So our Google searches where actually, '3 things not to do when welding'

    After weeks of practice, our welds looked just like yours. We had a hard time controlling heat, 'pushing' the weld puddle, and getting proper penetration. About 4 mos into our practicing we acquired a Miller Syncrowave 250 and then invited a welding instructor out for a weekend of instruction. THIS CHANGED EVERYTHING. The very first time I witnessed him run a bead, all the lights went on and I immediately realized the changes I needed to make. I'm posting the photo below as an example from our website. If I was at my home computer I'd post a comparable early weld photo that would look just like yours. It just takes some guidance. I'd recommend some personal instruction from someone who can help teach you. You'll be a better welder that same day


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    Thanks CBaron!

    I have looked some at Miller line of welders and am really thinking hard about getting a 150 STL. Getting my own welder would also provide me more time for practice because as ByStickel pointed out I really need some hood time.

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    Since welding practice is the topic....

    While saving up for a proper TIG machine, would it make any sense to buy a cheap MIG set up to mess around with in the mean time?

  26. #26
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    Totally different

    You won't learn anything very useful for building bikes or TIG from welding with MIG, but MIG machines are cool to have around for making big stuff where laying a TIG bead would take forever (and/or you're not overly concerned about the appearance of the weld).

    They are totally different tools for different tasks, so if your goal is to save up for a TIG machine, MIG will only set you back. If you want to do general welding, MIG is a great tool to have available.

    -Walt

    Quote Originally Posted by eMcK
    Since welding practice is the topic....

    While saving up for a proper TIG machine, would it make any sense to buy a cheap MIG set up to mess around with in the mean time?
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  27. #27
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    Thanks Walt!

    What do you think of the cheap TIG machines like Harbor Freight has?

    Also, what about mid priced Miller machines like the 150 STH? I was looking at the 150 STL as well but the STH has high freq start and pulse although from your earlier posts and other stuff I have seen it seems pulse is not a requirement.

  28. #28
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    I'm curious what experience you've had with TIG welding other than on tubing. Tubing adds a lot of complexity due to the need for good miters and the changing angles and surfaces.

    my $.02

    You can make some really good progress with a couple evenings running beads on flat plate to work on hand and foot coordination. I'd even suggest forgoing the filler rod for a bit and just working on pulsing with your foot to get nice even dimes with consistent overlap. Once you can do that start dabbing in with the filler rod and progress from there to butt and T joints where you'll develop a feel for where to point the tungsten. Only when you can do those with some degree of confidence would I go back to tubing. At that point your improved coordination will allow you to move faster and things won't get so hot.

  29. #29
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    150STH is awesome

    If you are mostly interested in bikes (and don't care about being able to run AC for aluminum) the Maxstar welders are an awesome deal. I have one (150STH from when that machine first came out 7ish years ago) and built probably 150 bikes with it before upgrading to a Dynasty (which, to be honest, is overkill for what I do, but it seemed like the cool thing to have at the time). The autoline/110 feature is really nice if you don't have access to a 220 circuit, too - the 150STH will run just fine for bike work on any old 20 amp 110 circuit.

    If you want to be able to do higher amperage work and general welding (ie, thicker materials), or work on aluminum, the Maxstar is the wrong choice, though.

    IMO, pulser isn't that important. Many people love them, I used mine for a while and then stopped using it, and I can't really tell a difference. YMMV. The high frequency start is a very good thing to have.

    I have never used the Harbor Freight welders, but my guess is that you get what you pay for (ie, they probably kinda suck). If you want to make bikes for cheap, just go O/A and fillet braze. TIG is cool, and it's fast if you're good at it, but it's not inherently better than any other joinery method, and it's wicked expensive. So if money is a big concern, TIG is not the way to go.

    -Walt

    Quote Originally Posted by markfarnsworth
    Thanks Walt!

    What do you think of the cheap TIG machines like Harbor Freight has?

    Also, what about mid priced Miller machines like the 150 STH? I was looking at the 150 STL as well but the STH has high freq start and pulse although from your earlier posts and other stuff I have seen it seems pulse is not a requirement.
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  30. #30
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    Quote Originally Posted by graviT
    I'm curious what experience you've had with TIG welding other than on tubing. Tubing adds a lot of complexity due to the need for good miters and the changing angles and surfaces.
    Thanks!

    My experience with TIG is about six short sessions at the tech shop plus about a day of instruction from the 5 day BREW class.

    The place I go now is Tech Shop RDU (a monthly dues based workshop). The shop is really great but having my own welder at hope is going to make me better faster plus it is part of the master plan.

    For the miters, I am doing them by hand on a grinding wheel. In truth the miters are actually really good even if I do say so my self. I have some gaps that are the thickness of a sheet of paper but not many and really they are much better miters then the ones I did in the frame building class. My sense is that a really good hand on the torch can compensate for some miter gaps. I like hand miters and figure a grinding wheel and some files is way more in my budget vs. a milling machine and regardless I like working with my hands and don't really like milling machines (I owned a CNC at one point and am glad to be free of it).

    In any case I am on the fence about buying the 150 STH. It is lots of money but then again it is something I want to do and really at the end of the day it is not going to break the bank plus practice will be much easier if the welder is here vs. going to the TechShop when I feel the itch.

    Thanks to all!

  31. #31
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    Quote Originally Posted by Walt
    Maxstar welders are an awesome deal. I have one...

    -Walt
    Have a PC-300 you'd want to sell off?

  32. #32
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    Quote Originally Posted by markfarnsworth
    My sense is that a really good hand on the torch can compensate for some miter gaps.
    Any gap is going to require more heat input as you shove filler in to close both shoulders, and that is going to saturate the thin material with heat. Your miters should hold water. Prep is everything with tig; fit up, cleanliness of the parent/filler/electrode etc... Thin tubing is much different than running a open root pass on thick pipe or plate.
    Last edited by kampgnar; 01-30-2011 at 06:29 AM.

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    A great target to aim for, but...

    There is no point in scaring people away by making claims like that - you do NOT need watertight miters to make a good and safe bike. You certainly don't want big gaps, but the OPs "difficulty slipping a piece of paper in" is more than good enough.

    This is a bike, not a satellite or a fighter plane. Tight miters are great - they help keep things straight when you join your tubes, they make it easier to weld/braze/etc. But perfect miters are an abstract goal, not a requirement for a fun bike.

    That said, I agree that setup and preparation are always important, regardless of your joining method. Do the best miters, cleaning, and joining you can.

    -Walt

    Quote Originally Posted by kampgnar
    Any gap is going to require more heat input as you shove filler in to close both shoulders, and that is going to saturate the thin material with heat. Your miters should hold water. Prep is everything with tig; fit up, cleanliness of the parent/filler/electrode etc... Thin tubing is much different than running a open root pass on thick pipe or plate.
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  34. #34
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    One thing that I really liked about the BREW frame class is that we did all the miters with grinding wheels and files. For me this makes building bikes in my home shop much more possible vs. having a milling machine. The miters on my class bike were not perfect and the bike welded up with good alignment plus it rides great. I am sure that the miters on my first home built bike will be better because I am not in any rush and I can spend lots of time with the file to make it as good as humanly possible. If I can make them hold water I will.

    My welding practice miters might be a little sloppy but given the discussion I will tighten them up a bit ( perfect practice makes perfect ).

    -Mark
    http://febikes.wordpress.com
    BTW: I have now changed my forum name from markfarnsworth to febikes in the interest of having a shorter handle.
    Last edited by febikes; 01-30-2011 at 04:20 PM.

  35. #35
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    Quote Originally Posted by Walt
    There is no point in scaring people away by making claims like that - you do NOT need watertight miters to make a good and safe bike.
    Figure of speech. I don't think that substituting torch manipulation for initial fitup is "best practice".

  36. #36
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    Thanks for all the info in this thread!!! I tried some of the suggestions and it really made an improvement on the practice welds I did this afternoon. All the little suggestions and tips really help out when learning, and the items shared so far are great. The pic below is on some scrap tubing and is getting better...


  37. #37
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    Rad!

    That is looking awesome!

    I think this thread might deserve a link in the FAQ. Lots of good info for folks who want to learn to TIG.

    Edit: Linked in the FAQ. Keep the progress reports coming!

    -Walt
    Last edited by Walt; 01-30-2011 at 04:44 PM.
    Waltworks Custom Bicycles
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  38. #38
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    I'm pretty stoked on this thread too. Just finished my taxes, a welder may not be as far in my future as I expected...

  39. #39
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    Quote Originally Posted by tamen00
    I tried some of the suggestions and it really made an improvement on the practice welds I did this afternoon.
    WOW! That looks awesome (although I am a newbie and not the best judge).

    Can you share what TIG machine you are using and the settings you are using?

    I am still trying to wrap my mind around how much of the pidgin poop look in my welds comes from the limits of the Hobart TIGMATE and how much is pilot error. I figure for the next three months I am going to practice on the Hobart but after that I am going to be looking really hard at an equipment upgrade. My guess is that most of my issues are from lack of skill but for at least some of it I feel like I might want to blame the machine.
    Last edited by febikes; 01-30-2011 at 05:45 PM.

  40. #40
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    My machine is a Lincoln Precision Tig 225 that I picked up off of craigslist complete (and almost brand new). I used 40 amps for the practice weld (.8 to 1.0mm tube), 1/16 Lanthanated tungsten, .040 filler wire. I also had the pulser on the machine turned off - seems I can do better using the foot pedal.

    I think that I need to move a little faster to make the HAV smaller and not heat stuff up so much - but just turning down the amps (I was using a lot more) really helped a lot (as suggested in this thread!!)

    Also, FEbikes - my welds looked like yours not too long ago. I was lingering in the same spot too long with the pedal kind of halfway pushed down, and not really letting up when moving to the next spot if that makes sense. Now I am pushing the pedal more, and letting up more - giving more heat when adding filler and way less when moving to next spot - more drastic "pulses". I also added a gas lens a little while ago, and turned my gas down to 18cfm (I had like 25-30 and I think it was causing issues).

    Super fun but frustrating learning how to do this. I have an opportunity to meet with a very experienced frame builder friend of mine over the next few weeks so that should help a lot also - getting to see someone that knows what they are doing do it!!!
    Last edited by tamen00; 01-30-2011 at 07:51 PM.

  41. #41
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    I when ahead and bought a maxstar 150 STH.

    I am already much happier with my results but still have a long way to go.


    Thanks to everyone who provided tips on this thread!
    Last edited by febikes; 02-25-2011 at 07:06 PM.

  42. #42
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    So I am doing practice welds on scrap tubing with the range dial set at 40 amps. I am also doing a bike build as well and using 40 amps for most of my bike build but in some areas I seem to need more heat. Do people who weld bike frames turn the dial up and down for the various joints or do you just keep it set at 40 amps?

    40 amps feels good for most areas but I have been thinking about setting the range a bit higher so I can get the puddle to form more quickly then feather back on the pedal. Is it a bad idea to set my welder for 50 amps?

    For the weld of the rear brake mount I felt I needed a lot more power and turned the dial up to 60 amps then tried to focus most of the heat on the thick metal plate because without the extra kick I could not really get a stable puddle. Am I crazy to think about using 70 amps next time for this weld?


  43. #43
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    In general you want to set the range of the pedal to more than you need continuously. Then you can stomp on it at the beginning to get heat quickly and taper off as much as needed. How much more is only limited by the sensitivity of your foot.

  44. #44
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    That grey scale is an indication that you've cooked your workpiece and/or neglected to shield the puddle from scaling over. Attempting to weld with insufficient amps is a cause, as is insufficient argon coverage. The remedy is bump up the amps so that your puddle forms quicker and you're moving at a steady pace (not fighting to get the puddle moving). Also make sure that your using a gas lense ($30 set on ebay) with a sufficient CFH and post flow to prevent scale.

    You will likely find that there are a range of amps that are required to maintain a stable puddle size. The thicker areas will require more amps, (my dropout areas require ~62-66 amps with .049 stays and ~56-59 with .035 stays) and the sharper corners usually require more as well. My frames typically range form 46-67 amps using thoriated tungsten.(tungsten types can affect these amp ranges as well.)

    Most will say that overshooting the amps by ~15% and backing off is the best way, though I find myself burning too hot with this method. My method is to write down the typical amp range and overshoot by a few amps.

    If the puddle is too cold it will be slow to move and will be noticeably small. Dont weld too hot either, you'll move too fast and end up with an insufficient gas coverage, cooked heat affected zone, holes etc.

  45. #45
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    Quote Originally Posted by mattty
    That grey scale is an indication that you've cooked your workpiece and/or neglected to shield the puddle from scaling over.
    Thanks! I am using a gas lens at 15 cfh flow rate. I think the issue here was that the weld would be better with more amps and faster travel. Hopefully the bike won't fail to quickly as a result of "cooked workpiece". This bike is for me as my learning bike so I won't worry too much if it cracks in this area other then to take it as lesson.

  46. #46
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    Another big thanks to everyone who contributed tips to this thread.

    I am making progress and much happier with my welds today. They still have a long way to go but with some more torch time and more tips from the forum I continue to make progress.

    One thing I am still concerned about is shielding. This weld was done with a #7 gas lens and about 15 cfh flow rate using 70 amps, 1/16th thorated, and .035 rod. I got a bit of dark blue / purple on some sections. The following is a picture of the worst purple section.

    The purple brushed off easy but it makes me wonder if I should be using a bigger gas lens or more flow. Is this purple something to worry about?



    After a couple of brush strokes the weld looks okay.



    I am not yet setup for back purge but it is on my short list.

  47. #47
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    What is the ideal weld cross section?

    In terms of bead size what is the ideal cross section?

    What do you guys think? Is the fillet on this weld big enough?

    What is ideal and where do you start to get concerned?


  48. #48
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    Quote Originally Posted by febikes View Post
    In terms of bead size what is the ideal cross section?

    What do you guys think? Is the fillet on this weld big enough?

    What is ideal and where do you start to get concerned?
    to my uneducated eye that cross section looks like good penetration but fairly concave, I have read that a more concave weld profile causes internal tension and that it's better to have a weld with a more flat/angular profile. also the concave profile comes alot closer to being undercut.

    I am in this practice/learning phase myself with a bunch of .049x1.0 chromoly and similar. 49 amps, ER70s-2, ~16cfh, 1/16th tungsten unknown type, no gas lens, somewhat sloppy miters and also getting the concave, lightly oxidized bead surface. but I did a test break and it popped out of the vice before it bent more than 20* and no cracks at all just kinked the short T piece that was held in the vice.
    I'm thinking that I'm using too low amps. I use basically this same exact setup on some furniture parts just bumped to 130a on cold rolled 1018 3/8 rod to some sort of sch40 3" pipe and the welds come out rainbow. still a tad hot and undercut, i think i need more filler or just to get the filler hand more dialled.
    one thing I noticed is the welds improve when i stick my hood right up in there, 8" or so from the weld.

    how far are you guys able to go around a typical 90* joint without stopping? I feel like on these type of round tube joints I am having trouble pivoting my wrist to get more than say 90* worth of tube.

  49. #49
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    Quote Originally Posted by sonic reducer View Post
    how far are you guys able to go around a typical 90* joint without stopping? I feel like on these type of round tube joints I am having trouble pivoting my wrist to get more than say 90* worth of tube.
    Miller welding recommends doing tubular welds in short sections. I have been tacking and then welding about 15-25% of the tube at a time.

  50. #50
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    Looks good to me. Concave is good as long as you don't undercut. The weld is already significantly thicker than the tube so you really don't need more. Other advantages are it doesn't produce a stress riser from a sudden change in cross section, a smooth transition makes it easier to see a crack if one does start, and it just plain looks better

    Im pretty sure I can't do 90deg in one shot on thin stuff where I have to reposition my wrist and keep the arc length really short. Probably closer to 45deg.

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