Where can I get a bike tube set?

http://www.framebuilding.com/
http://www.cycle-frames.com/bicycle-frame-tubing/

You might like the Framebuilders group
https://groups.google.com/group/framebuilders/about

It just moved to Google groups a month ago
You can search many years of postings at the old location
http://www.phred.org/pipermail/framebuilders/

Also I posted a boatload of framebuilding links in this old thread
http://www.fluther.com/89336/i-want-to-make-bicycles-am-i-crazy/

Good luck! That is a great endeavor!

You can get them at any bicyclle shop and I have aso seen them at Walmart.

@kitkat25 , I think the OP is asking about the tubes used in frame construction, not inner tubes. Although I haven’t been to Walmart recently, so I don’t know what they’re carrying.