Headtube distortion

[jbucky1]

Newbie question warning. If you dont like newbie, read another thread.

(steel) so when you tig weld the top tube and the down tube to the headtube, is it normal that the "roundness" of the headtube gets distorted? (ovalized)

If it is normal, what are the main factors that create the distortion and can they be minimized or ever eliminated with TIG?

cheers

[bellman]

Step one: email eRichie for clearance to the framebuilders section.

step two; post question there.

heating one side of the tube will distort it.

one way around this is to use a heatsink, opinions on this are varied. Basiclly the more experienced you are with heat control the less you will need one.

as a beginner you may may be moving slower than necessary and putting extra heat into the job. Use as thick as wall head tube as possible. True temper 37mm is good for this

It may be counterintuitive but higher amps and faster weld speed will result in less distortion.

Don't worry about being a newbie, ask away.

[Too Tall]

Jbucky1 , hang tight I'll add you to the eff'builders group and move this thread. Thanks for your participation.

[WadePatton]

all metal tubes distort when heated to the point of joinery by fusion welding or brazing. this should be anticipated and methods employed to minimize.

as Bellman implies, running a smaller flame or lower amperage exacerbates the problem because you spend more time to do the work _time at temp_ and this enlarges the HAZ and distortion.

So "hot and fast" is the mantra of those working with thin-walled stuff.

But blowing holes through your work is distortion of another sort, as is cooking your flux or solder.

i'm just throwing "theory" out there. I've welded, but am no tigger. i've only used o/a torch on bike frames.

practice and ask.

[Dornbox]

Mitering accuracy, heat control, and a heat sink if you have one and try not to do long beads if you feel like you're going slow but just can't go quicker. Also let the piece rest if it gets hot hot hot (beads are gray).

I stopped using my heat sink for a while without issue and I generally use less amperage to get smaller welds. Although, now I use a heat sink religiously which allows me to use more amperage and yet still move at a more leisurely rate. Find your own rhythm and combo.

At this point my guess is you're putting too much amperage into it and moving to slowly. Order some .075 4130 from dillsburg and practice your heat control. My amperage is set between 35 and 38 for everything without using a pulser. Call Jeff at Sputnik Tool for a heat sink. Best-Chris

[e.Gellie]

For fillet-brazing, steel discs made from 3/8" or 10mm material, that are tight fit into the head-tube work for me. A bolt threaded into each enables you to pull them back out of the head-tube when you're done.

Brass head-sinks for TIG welding.

Ewen Gellie

[Whipsmart]

This is more of a general TIG welding comment, but related to head tube distortion (and you might already well know this):

Use around 1 amp per .001" material thickness that you are welding, and then give yourself an additional 10-20% amps. Like others are saying, using lower than necessary amps causes you to stay in one area longer, and so heat soaks into the surrounding area, increasing the distortion. You want to get in, then get out for best results. I like pulser settings where the % on-time is relatively short (less than 50%), and the background amperage is relatively low (25-50%, depending on circumstances). That allows you to apply enough heat to fuse your materials quickly, then the heat backs down freezes the puddle, gives you plenty of time to move to the next puddle, and continues. Get in, get out, move on, quick.

Distortion of head tubes happens even if you are an excellent welder. You certainly can minimize it, even to the point that you can probably fit a headset without reaming, but I'd always ream a headtube to size anyway.

[jbucky1]

Thanks for the replys. Great stuff, cheers.