View Full Version : Donor bike is chomoly tubing...should I not bother..?

04-10-2012, 11:49 AM
Should I not bother to salvage headtube, bottom bracket etc from a frame like this? Looked around a bit online and get all kinds of conflicting messages about the abilities of welding this stuff to mild steel etc, especially with a MIG welder.

Old Peddler
04-10-2012, 12:15 PM
Chromoly Is a very strong tubing. It is what you want. There is no problem to weld it especially with a Mig. I do it every day. You just have to keep in mind that it is a thin material and you need to keep the voltage turned down a bit. As you know Mig is very controllable.

04-10-2012, 12:33 PM
Thanks OP, I am a total greenhorn in the welding department, have a nice little MIG 140 outfit to start climbing the learning ladder. I am keeping any and all scrap tubing from bikes I am getting so to practice welding them etc...I had just read so many conflicting things about chomoly that thought it was something for a new guy on the block to steer clear of.

04-10-2012, 04:09 PM
Its not a problem for us. The main reason against welding it to mild steel is the moly gets a little bit brittle in the heat affected zone and can crack there.
However, thats in high stress work such as air frames.
I use gas shield mig and never found it to be a problem.

04-10-2012, 05:40 PM
Thanks for the replies, I am keeping as much of the scrap pcs of tubing I can, in order to practice my welding with them. Will be a bit tho...the price of getting that first tank of gas for the mig is pretty steep. Until I get that, can only use welder with the flux core, which according to what I've read, isn't as suitable for thinner materials.

04-11-2012, 08:27 AM
I dont know if it will work with gassless but I find that welding vertically downwards helps on thin materials.

04-13-2012, 01:20 AM
Try and pre-heat the tubes with a blow torch or oxy-fuel setup. Keeping the cro-moly from cooling too quickly is the key to preventing cracks.