SF Cyclotouring

Ride reports and other ramblings from a San Francisco cyclist.


UBI Framebuilding Class - Day 1

5/11/2015 - Day 1

UBI Desk/Drafting Table

UBI Bench Area

My Bench.

Victor  Journeyman Oxy/Acet Torch Rig at UBI

Silver brazing Bottle Bosses

Lug practice: Fitting the "top tube" to the lug.

Silver Brazed Head Lug, Post Soak -- Left side

Silver Brazed Head Lug, Bisected
  • General info
    • Instructors: Joseph Ahearne & Dan Harrison
    • No eating/drinking at workbenches
    • Daily class checklist
    • QPB & Chris King orders
      • Cost + 15%
      • Orders needed by lunchtime on Friday
      • Can only buy things here while attending a UBI class
      • Check the online catalog
    • Kasai tubing catalog
    • Henry James catalog
    • No disk brakes on forks built in class
    • For fillet builders, you start on the main triangle first
    • For lugged builders, you start on the fork first
  • Jigs used in class
    • Henry James is used for lugged construction
    • Arctos is used for fillet construction
  • Torch Setup
    • Acetylene set to 5psi
    • O2 set to 10-12psi
    • Connections at regulator and valves are brass, so don't overtighten these!
    • Turn off Acet first, then O2
    • Bleed Acet from hoses first, then O2 -- this way the O2 pushes out any Acet left in the lines
  • Torch Flames
    • Reducing flame is used for Silver brazing ~ 1-2" secondary cone
    • Neutral flame is used for Brass brazing
      • Just a slight roaring sound
      • primary and secondary cones are equal length (they converge)
    • Oxidizing flame -- never want this
  • Flux
    • Blue flux for brass, thick consistency
    • White flux for silver, thin consistency & use a lot more than you think you need
    • Watch when the bubbles stop, which means you're near the working temp for the flux & filler
  • First demo & practice - Brazing water-bottle bosses
    • Drilling holes (#3/0.25" drill bit)
    • Use tubing block
    • Deburring
      • Deburring tool, move in clockwise direction only
      • Use half-round file inside the tube
    • Emory Cloth
    • Rubbing Alcohol to clean anything oily
    • Clean the silver filler wire with Scotchbrite pad
    • Heat the tube, not the H2O boss
    • "Paint" with the torch flame
  • Second practice - Lugs
    • Headtube/downtube lug: 60°
    • Headtube/toptube lug: 70° (start with this lug)
    • Seattube/toptube lug
  • Lug Prep
    • Never fit the tube to the lug, always fit the lug to the tube (e.g. never remove material from the tube, only the lug)
    • Remove burr from cut edge of tube with 2nd cut file
    • Lug should slide on tube under its own weight (loose fit)
    • Lug sockets are often oval due to casting process -- especially at thicker sections of casting since the cooling metal contracts more here
    • Choose a file that matches the lug socket radius
    • File in a criss-cross motion
    • Be careful not to over-file the lug's points
    • NOTE: Don't make the lugs loose on the tubes until after the tube is mitered!
  • Tube Mitering Demo
    • Push tube to meet the deepest points of the lug socket
    • Scribe lines on tube
    • Use metal snips or hacksaw to roughly trim the miter
      • Red snips - CCW / right-hand cut
      • Green snips - CW / left-hand cut
    • Position tube in block, aligning miter with block seam, clamp in bench vise
    • Try to file parallel to the floor, tilt the file slightly to bias material removal
    • Ensure the mating tube sits squarely and completely in the cut miter
      • If there are gaps at the sides of the valley, remove material from the bottom of the valley, possibly with a narrower file
      • If there are gaps at the bottom of the valley, remove material from the sides of the valley
      • Look for full contact around the perimeter of the miter
    • Use the lug to check the tube angle
  • Lug Brazing Demo
    • Applying Flux
      • 1/4" up inside of tube
      • All around the outside
      • Inside of lug completely
      • Make sure tube is seated at miter
      • 5mm excess headtube protruding from lug - gives a place for excess silver to flow onto
      • Flux outside of lug completely
      • Dry off flux with torch
    • Sequence
      • Wherever you add filler, the angle of the joint will pull tighter
      • NOTE: Always tack in plane to the frame
      • NOTE: Tack inside/obtuse angles on center first
      • Then tack on acute center line (other side of lug joint)
      • Finally go around right and then left side of lug to fill in with silver
      • The sequence is important because it keeps things centered and ensures the order of completeness -- silver penetration all around and through the lug
    • Flux should be evenly hot and clear on all joined surfaces -- watch for bubbles to stop coming out from the lug's edge
    • Don't heat any points on the lug directly, else they'll overheat
    • Tack just to the side of any lug points
    • Preheat where you want silver to flow


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