I have a lugged Meile road frame made out of Ishiwata 22 quadruple butted tubing and it has a 1 centimetre crack in the downtube near the bottom bracket. Is this frame repairable?
Could you post a picture? Did any specific event spur this damage, or did you just happen upon it one day? I tend to be optimistic, so I would say its repairable. Almost any steel is repairable, it may not be pretty afterward if the damage is real bad (yours doesn't sound real bad) , but repairable nonetheless.
Where are you located? If you're anywhere near Madison WI, I may be able to help you out.
you can try drilling small holes at the end of the crack 1/8th inch or so. do your best to clean the site off and try to find the very tip of the crack and drill a hole there. it is extremely important to hit the end of the crack. How/why it works... in steel cracks propagate due to shear. one factor that effects how cracks propagate is the "radius" at the tip of the crack. typically this is very small. so if you drill a 1/16th or 1/8th hole you have increased the radius at the end of the crack by orders of magnitude, thus increasing the stress that needs to be applied by orders of magnitude for the crack to propagate.