The Basics

- The wikipedia for "Bicycle Frame" is pretty good: http://en.wikipedia.org/wiki/Bicycle_frame
You'll want to memorize the frame tube diagram.

- Keep in mind these abbreviations:
TT: top tube
DT: down tube
HT: head tube
ST: seat tube
BB: bottom bracket shell
SS: seatstay(s)
CS: chainstay(s)
FB: fork blade(s)
SC: steerer column
DO: dropout

Email list, web forum
- The [Frame] listserv
Subscribers include many prominent pro builders, as well as talented hobbyists.
http://www.phred.org/mailman/listinfo/framebuilders
The archives have 15+ years of searchable archived discussions: http://search.bikelist.org/
- Frameforum.net


Frame Design
Everyone and their mom has a different opinion.

- Strawberry has instructions for measuring someone and a calculator to determine frame sizing from those measurements:
http://www.strawberrybicycle.com/frames-custom.php

- The Bike Geometry Project is a database of frame designs from the past:
http://home.comcast.net/~pinnah/dirtbag-bikes/geometry-project.html

- You may want to look for a geometry spec sheet for a bike you've ridden. Maybe you want to make something similar with a little tweaking, or maybe you want to make something totally different. Your best bet is probably the manufacturer's website.

Materials
The main bicycle tubing brands are:
Columbus
Reynolds
Dedacciai
True Temper (see Henry James below)
Some say Deda tubes generally have more of a bow than others, e.g. Columbus. Deda is usually the cheapest of these 4 brands.
Reynolds stuff seems to be harder to get in small quantities. There's enough good stuff available that I haven't really tried.

Suppliers for framebuilding-specific materials and supplies:
- Ceeway http://ceeway.com/ UK
Big selection, both old stuff and new stuff. Lots of old lugs. Columbus tubes. Even though they're in the UK, they can be cost competitive with more local suppliers. Peter runs the place...nice guy. Email for a price list.

- Nova Cycle Supply http://novacycles.com/ CA
Good selection, though not as big as Ceeway. Columbus, Deda, and Nova brand (CrMo) tubes.

- Bringheli http://bringheli.com/ OH
Joe Bringheli sells Columbus and Deda tubes, Walter lugs. Good prices, good service.

- Pacenti http://bikelugs.com TN, moving to west coast
Kirk Pacenti designs and sells high-end frame parts (lugs, BBs, fork crowns, etc.). Some of the nicest frame parts available. A few tubes from Columbus and others.

- Henry James http://henryjames.com CA
True Temper tubes, made in the US. Henry James lugs, which are good quality. Some prices at the higher end. Tubing selection is broad.

- Kalavinka http://www.kalavinka-bikes.com/ Japan
Lugs designed specifically for track bikes. Super thin cast lugs. Surprisingly fast shipping.

- Strawberry Portland, OR
Andy Newlands sells a few Reynolds tubes along with his cast wishbone parts.

- UBI Ashland, OR
UBI has Kaisei tubes as well as some frame parts from Paragon Machine Works. Paragon also sells direct.

Bicycle tubing is generally butted for durability and weight savings. Non-butted, straight-gauge 4130 aircraft tubing is cheaper, heavier, and stiffer (all else equal). It's great for brazing practice, and we have plenty for that purpose. Also used for making racks, SS or CS bridges, stems, even chainstays and seatstays sometimes.
Suppliers include:
Wick's Aircraft
Aircraft Spruce

Deciphering tubing offerings
Distributors may sell tubes in sets or individual tubes or both. Bringheli does both, depends on the tube. Nova sells individual tubes but they often have special deals on complete sets.

7/8" = 22.2 mm (round chainstays)
1" = 25.4 mm (TTs)
1-1/8" = 28.6 mm (STs, DTs, TTs)
1-1/4" = 31.75 mm
1-3/8" = 34.9 mm
1-1/2" = 38.1 mm (approx. outside diameter of a typical BB shell)

On tube diameters:
- The dimensions for traditional front triangle tubes are:
25.4 mm TT, 31.7 HT, 28.6 ST, 28.6 DT
Typically the rear triangle would be 22.2 round CS and 14 mm round SS.
- Then they started doing "oversized" tubes, i.e.
28.6 mm TT, 31.7 HT, 28.6 ST, 31.7 DT
30 x 17 oval CS and 16 mm round SS are also oversized tubes.
- Nowadays the term "oversized" is a little too vague to be practical--there are too many flavors of "oversized". A broad range of main triangle tube diameters is available, from 25.4 mm TTs up to at least 42 mm DTs. Seatstays are available up to at least 19 mm. There are also some shaped tubes available, i.e. neither round nor oval, for TTs, DTs, SSs, CSs, even a couple FBs.

On tube stiffness:
A tube's diameter is a much bigger factor contributing to its stiffness than its wall thickness. That is, if you want to increase stiffness, you want a larger-diameter tube; increasing tube diameter, even if you decrease wall thickness, will generally give you a lighter, stiffer tube.
Even a small increase in diameter has a large impact on stiffness. At some point, however, the walls get so thin that denting can be a problem.
For example, let's compare a Columbus SL 25.4mm .8/.5/.8 TT with an otherwise-identical 28.6mm .7/.4/.7 TT. The latter weighs 12 grams less, but is 20% stiffer @ 200 lbs simple deflection.
To nerd out more on tube stiffness, check out this tube calculator from Don Ferris at Anvil.

On alloys:
Each manufacturer offers tubes in a few different alloys. Typically their budget-price alloy (e.g. Reynolds 525, Deda ZeroTre, Columbus Zona or SL) is, basically, 4130. Higher prices usually buy harder, thinner-walled tubes, which are harder to braze and more likely to dent.
The alloy has no effect on the stiffness of a tube. In engineering-speak, all steels have (very nearly) the same Young's Modulus.
A more expensive alloy may be stronger, thereby allowing tubes to be drawn with thinner walls without sacrificing (much) dent resistance.
Two identical tubes, one made from Columbus Spirit, the other from Columbus Zona, will be equally stiff, though the Spirit tube will be more expensive and harder to miter.
High-end alloys may be more brittle, which is why fork blades are made from low-end alloys.

A frame for a 1"/25.4mm fork should have a 31.7 mm HT. A frame for a 1-1/8"/28.6mm fork should have a 36 mm HT. The frame doesn't care if the steerer tube is threaded or not, but the headset does.

Framebuilding classes
Doug Fattic in Niles, Michigan. Email Doug for a schedule.
Dave Bohm/Bohemian Bicycles in Tempe, AZ
UBI in Ashland, OR
Yamaguchi in CO