This video documents a manual machining project to modify a custom-made aluminum brake caliper bracket for a friend's Harley-Davidson motorcycle. The primary challenge is milling two pockets that are not at a 90-degree angle; the required angle is measured to be 114 degrees. To accomplish this, the project is set up on a KBC manual mill using a vintage 12-inch Universal rotary table. The video details the meticulous process of cleaning, mounting, and precisely centering the heavy rotary table and a custom fixture plate. A key part of the setup involves visually aligning the workpiece's layout lines with the mill's axis of travel using a scriber. The pockets are then machined to a depth of 0.165 inches using a 5/8" Tungaloy indexable endmill, with the rotary table used to accurately create the 114-degree corners. The project concludes with a successful test fit of the brake caliper, showcasing a classic example of precision problem-solving with manual machine tools.
Precision Machining a Custom Motorcycle Brake Bracket
00:00:18 Project Introduction: The task is to machine two pockets into a custom, handmade aluminum brake caliper bracket for a friend's Harley-Davidson motorcycle. The pockets need to be milled to a depth of 0.165 inches.
00:02:27 The Angled Pocket Challenge: The pockets are not a standard square shape. A protractor is used to measure the angle on the caliper itself, revealing it to be 114 degrees, making it a perfect job for a rotary table instead of simple X and Y-axis milling.
00:03:41 Preparing the Key Tool: A vintage, high-quality 12-inch Universal rotary table, weighing 136 lbs, is thoroughly cleaned and oiled. Its hand-scraped surfaces are highlighted as a sign of quality, allowing it to glide smoothly on the mill table.
00:10:53 Centering the Rotary Table: A test indicator is used to precisely align the rotary table's center bore with the milling machine's spindle, ensuring the axis of rotation is perfectly centered. This is a critical step for accurate work.
00:18:18 Workholding and Alignment Setup: The aluminum bracket is clamped onto a custom fixture plate using non-marring brass strap clamps. A scriber is mounted in the mill to visually align the layout lines on the part with the mill's X-axis travel before locking it down.
00:28:23 Cutter Selection: Using a radius gauge set, the corner radius is determined to be 5/16", necessitating a 5/8" diameter cutter. A Tungaloy "TungForce-Rec" indexable endmill with aluminum-specific cutting inserts is chosen for the job.
00:33:41 Machining the Pockets: The first pocket is cut by milling one side, rotating the rotary table by 14 degrees, and then milling the second side to form the 114-degree corner. The process is then repeated for the second pocket on the opposite side of the bracket.
00:44:42 The Perfect Fit: After machining and deburring, the brake caliper is test-fitted into the new pockets. It fits perfectly with a uniform clearance, confirming the success and accuracy of the manual machining setup.
00:47:38 Final Thoughts & Next Project: The narrator emphasizes how this was a fun project that perfectly demonstrated the value of manual machining skills and tools like the rotary table for one-off custom jobs. He also previews the next project for the same bike: creating an adapter to convert it from a chain drive to a modern belt drive.