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This is my framebuilding jig, shown set-up for a single bike frame. The jig converts from single to tandem configuration in about a minute. Most measurements I need are scribed on the jig, so I can set up a complete frame geometry in minutes.

Here's the same jig set-up for a tandem frame. I designed and machined the entire jig myself, it's very solid and accurate. The main plate is machined from 1" aluminum plate and measures about 60"x30". The entire jig rotates in the vertical plane as well on a large bearing.

Here's a close-up of the adjustable tube-holders for the seat-tube. Every geometry adjustment is made independently on this jig.

The complete design  package for this jig is available for purchase, it includes details drawings of all components, a machine shop could fabricate right off the drawing package.

Here's the dropout clamping portion of the jig. I have 2 different dummy axles which work for 4 dropout spacings (120-145mm). Bottom bracket drop is fine-tuned via a threaded adjuster, and measured right off the scale on the jig. Same for chainstay length.

This is my cute little lathe. It's an old Atlas 6", which is small, but nice for turning small parts associated with bikes. I used to use this for mitering tubes as well, but since purchasing a mill, I only do turning on here now.

Here's how I used to miter tubes, on a tilting head vertical mill. The yellow thing in the picture is a hole saw used to cut the miter. I would clamp the tube in the vise, center it up, set the angle with the mill head and cut it in about 2 minutes. Not a bad method.

Here's what I use these days for mitering tubes. This is a Nichols PMC12 horizontal production mill with a huge Rockwell 15" rotary table mounted on it. The tube holding arrangement is my own design and build. There are 2 scales right on the tool to set tube length and miter angle. I literally just pull the values out of my design spreadsheet, set the tool and it cuts the exact length of tube at the exact angle I need.

This is my vertical mill. It's a Burke Millrite machine from the early 70's. Very nice, slightly smaller main casting than a full size Bridgeport, but same size table. Power down and cross feeds. I use this mainly for general machining, but also for mitering small parts like brake bridges.

This is my alignment table. It's machined from 1" plate steel, 3'x4'. The Bottom Bracket post was turned from steel billet. The whole table weighs in at about 600 lbs!

 

 


Copyright 2007 Bob Brown Cycles L.L.C.