Techniques

Framebuilding is an art that is filled with little tricks and techniques.  Below you will find a few that i have run across over the years, mostly from talking to other more experienced builders. If you have more to add, let me know.  In the meantime, have fun!

Internal Cable Routing

This is one that I did once, swore I would never do it again.  Then I did it again, couldn't resist.  It's a pain, but looks slick when it's all done.

Take a stainless steel tube, slightly larger in diameter then the cable housing for your cable.  Drill two holes in your top tube, one at either end.  Keep the holes in the section of the tube that still has the thick butting!!!  You will have to elongate the hole into an oval to get the stainless tube to enter the top tube at the correct angle, or else your brake cable will bind.  Set this all up BEFORE brazing the top tube into the lugs.  Then braze the stainless steel tube into place.

Once the stainless tube is in place, braze a reinforcing plate on top of it.  The reinforcing plate can be homemade, or stolen from something else.  Here I used a little reinforcing plate designed for use on a chainstay bridge. 

Here is the other end of the internal cable routing.  I have been told it is easier to run the stainless steel cable into the top tube if both entry and exit points are kept in the same plane, i.e. if standing at the handlebars and facing towards the back of the bike, the stainless  tube enters the TT at the 5 o'clock position, and then it exits again at 5 o'clock by the seat lug. 

Holding Braze Ons

Getting braze ons to stay in place is aggravating.  You can use a clamp like illustrated on the Tools page, or you can use magnets. 

Here is a magnet holding a cable stop in place.  Usually it helps to have 2 or 3 magnets holding the braze on in place.  Beware that as the piece heats up, the magnet will crack and explode, so work fast. 

 Building Lugs

To cut lugs, first you need a blank lugs.  Paint the lugs with a black magic marker, then scribe your pattern on it.  Then, cut it out using files and a thin saw.  You can see my custom lug page and the Labor of Lug article for more info.  Also, the lug mandrel used to hold the lug while you work can be seen on the tools page.  Adding a nicely shaped point or curve to a lug is easy as well: take a scrap piece of tubing, cut out a small triangle, and then brass braze the triangle onto the lug where you want it.  Then , file the transition from lug to point.  You braze it on with brass so that when you braze the whole lug into the bike, you can use silver and not melt the point off again. 

However, you need something to hold the lug and the point together while you braze the point on.  Here we have a scrap piece of tubing with a slot cut into it. 

Then, you place the joint between lug and point over this cutout.  The piece of scrap tubing supports the lug/point combination as you braze.  When you braze the point, the seam will be located over the slot, preventing you from brazing the point to the scrap piece of tubing behind it.  You could also use a piece of stainless steel pipe, since the brass won't stick to it.   In this photo, you can see a small horizontal line where point meets lug. 

Seat Cluster

There are many many ways to braze seat stays onto the seat tube.  This is one of the more visible parts of a bike, and also one of the places where a bike builder can really show off his work.

To build a fastback cluster, I start out with a seat stay and a lug that has ports cast into the back.  normally, you would insert the seat stays into these ports and braze, thus making a seat cluster.  Instead, I will use it as a pattern.  So first paint the seat stay black with a magic marker, and then stick it in to the port in the back of the lug. 

Here you can see the stay sticking into the back of the lug.   Now scribe a line around the inside of the lug and file the seat stay to the line. 

Here you have the seat stay with the end filed to the inside shape of the lug.

Now place the seat stay up against your lug.  It may require slight modification depending on what angle the seat stay approaches the lug and seat tube. 

Or you can make a side tacked seat cluster.  Take the end of a seat stay, and make a several inch long, 45 degree cut, which should end at the corner of the stay.   Then, take this piece of scrap tubing out.  Now, you can either  flip this scrap piece over and place it back onto the stay, or put a half piece of one inch tubing in the spot.   IN either case, braze around the edge, clean up the joint, and you have a nicely scalloped seat stay. 

Here is the 45 degree cut that ends at the corner of the stay.

Here is the one inch piece of half tubing that was laid in the spot after the cut, and it was brazed and filed clean. 

Another view of the above picture. 

Seat Binder Bolts

Many great lugs are made of stamped steel, which is formed into the lug and welded down the seam.  The seat binder bolt are for these lugs are somewhat ugly.  It is easy to change this with a little metal sculpting. 

Here is a beautiful stamped steel lug with an ugly seat binder.  

Here is a different lug, but with the binder tabs ground off.  Notice the hole that is left in the back of the lug once the tabs are gone. 

Here is the lug built into a frame, with a "patch" of steel brazed into the spot where the hole used to be.  In this case, the patch was cut from 4130 straight guage tubing (i.e. aircraft tubing) of the same diameter as the lug.  A few gaps still remain between patch and edges of the hole, but this is easily filled with silver brazing rod. 

Side view

Here is what it will look like, roughly, when all the brazing is done.  The seat binder is now a separate piece (which is cast) and then brazed in place. 

Bridges

Making brake bridges and chain stay bridges is also very easy. Just take a scrap piece of seat stay, miter the ends to fit the opposing tubes, and silver braze it in place.  It looks nice if you also use little reinforcing plates on either end.  These are usually store bought however. 

Here is just such a bridge.  It is drilled for a fender. 

Dropouts

Many fine dropouts are the tab variety: one flat piece of dropout, designed to insert into a slotted stay or forkblade.  Often they can be re-worked to look better.

Here are two dropouts.   The left is how it comes from the manufacturer, raw.  On the right it is brazed into a stay, but the filing and finish work is not yet completed.  I usually do the final finish work when the pieces are on the completed bike.  I removed one fender eyelet and ground down much of the excess metal on the back edge of the dropout.  Then i rounded it off and tried to make a smooth transition to the last remaining eyelet.   Further thinning and shaping will be done in the area of the seatstay once it is brazed in place.  Notice the chainstay junction on the non-drive side: it is scalloped.  This is performed by beveling the end of the stay at a 45 degree angle before inserting the dropout.  Once you start brazing, fill in this beveled are, and a little beyond the stay (toward the dropout slot) with brass.  Then take a sanding drum of the appropriate size, put in your dremel tool, and sand out a scallop. 

Here is the non-drive side of a similar dropout.  Notice how the stay is flattened to create more room for the rear wheel.  This is more critical on the drive-side dropout to make room for the cogs.  But, you can do it on the non-drive side for symmetry.  To do it, braze the outside surface of the dropout first, the one with the scallop.  Then heat the inside surface of the stay, bring over to a flat metal workbench, and hammer (gently!) the inside of the stay until it is flat.  Then braze around the edge of this flat part.  When everything is cool, file the flattened part to make it broader, smoother, whatever.  You can also file in a gentle curve to be more ornate. 

Here is the bottom of the stay.  Notice the scallop on the outside surface, and the flattened part on the inside (wheel-side) of the dropout.  Here, i decided to leave the wheel-side not perfectly flat, but with a little curve, to make things a little nicer. 

Thanks to David Bohm, Josh Putnam, Damon Rinard, Fred Parr, and others whose ideas and information have gone into this page.


If you would like to get in touch with me, please e-mail me at: root@student.uchc.edu

Created September 20, 1998. Last updated March 13, 2003.




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