Overview

Below you'll find a some of the CNC parts I've made in the Cal Poly machine shops. I machine parts for my own designs, friends, and my peers as part of my job as CNC supervisor.

For most of the parts below, I write about how I approached it and how I would correct mistakes. Please reach out if you see a better strategy for a part or if you think my conjectures are wrong, I'd love to learn more.

Mini Bike Dropouts

This is the second time I've made these dropouts, and I'm about to make them again. First I accidentally mirrored one of the parts so it didn't fit on the bike, and then I messed up the dropout spacing. It's been a good lesson in double checking dimensions and 3D printing designs before you invest the time in machining them.

Nothing too novel on these machining wise. I dialed in my thread mill parameters for the M8 bosses, so it should be a faster process in the future.

Frisbee Golf Disc

As CNC Supervisor, it's my job to make parts for my peers senior projects every now and then. The aluminum disc pictured below is two halves of a wheel designed to shoot frisbee golf discs. I didn't have much part in the design, but it was fun to machine. It would have been a better lathe part, but we only have TL-1 lathes and the fixturing was ready to go on the mill.

I did the surfacing with a .03 radius bull nose. It came out okay, but since this part didn't require smooth transitions between surfacing and other features, it would have made more sense to run a larger diameter ball mill. I already had the bull nose loaded, so it was easier just to run it.

Trophy Tiara

My friends and I had the pleasure of winning the last edition of the SLO little 500, a bike 'race' in town. With that honor comes the privilege of making a new trophy for the race. I was in the process of installing a fifth axis trunnion onto our new VF-2SS at Cal Poly, so I figured it was the perfect opportunity to make a sweet tiara.

I set up a full machine simulation in Fusion 360 along with the tool holders in our shops. I wouldn't run a multi axis part without having everything modeled, it gives a lot more confidence.

The surface finish on the facing operation gave me a little trouble. I had a finishing pass, but the roughing was aggressive enough that the finishing wasn't able to clean up all the gouging caused by my hefty roughing strategy. I think some of the gouging might have been from tram error, but I'm not sure. I indicated the platter of the trunnion in to one tenth over a 10 inch microflat granite bar so it doesn't seem like any tram error should have been this bad. If I could do it over, I would side mill the walls. The only reason I didnt was because I didn't have a long enough end mill, but I could have tipped it over on the fifth axis and surfaced the sections I couldn't reach. The 3D printed fixture made the thin features more machinable.

Stumpjumper Pivot Bolt

My pivot bolt fell out when I was riding down Rock Garden on Cerro. You can only buy pivot bolts as a set from specialized, so I machined one. I didn't incorporate the dust seal into the first version, but I plan to make another one with an internal hex and a seal.

Mini Bike Dropouts

I'm building a fork for my new commuter bike, and I decided to test out my new thread mill on the through axle receiver. These are very similar to the dropouts I machined for my friend Shaw's tall bike last year, so they went pretty quickly. I didn't bother with any pretty finishing passes because they're getting powder coated anyway.

Custom Chainstay Yoke

Kellen, one of my fellow bike builders wanted to get one last frame build in before he graduated. He designed a sweet yoke for the chainstay-bottom bracket junction, and I agreed to machine it for him on the VF-3SS.

Mini Bike Fork Crown

I'm building a fork for my mini commuter, and I need to machine the dropouts as well as the crown. The fork will have a 1/18" straight steerer tube and 1" fork blades.

Kinetic Energy Harvesting

Senior Project

I made several parts for my friend Shaw's senior project. One of them was quite large with a lot of surfacing. I was running a reduced neck long reach tool on this part, and I learned a lot about deflection and how much I can push carbide. I used a constant scallop heigher finishing toolpath for the surfacing.

If I were to do it again I would use a steep and shallow toolpath in Fusion or a couple waterline toolpaths with different Z stepdowns in mastercam to get a more consistent surface finish. It still turned out great, but I would have liked all of the toolpaths to line up.

Jack Points

I made these to locate jack stands for a friends tiny home build.

Braze Clamp

This is a tool to help hold parts onto bike frames while they are brazed. The design was inspired by a similar tool made by Cobra Framebuilding.

Post Mount Brake Adaptor

This part attaches a disc brake caliper to the rear end of the mountain bikes that I'm building for my brother and myself. It involved 3D surfacing with a bull nose end mill to reduce match marks, soft jaws, and it had three operations.

Op 1

Soft Jaws and Op 2

Op 3

Titanium Metal Spinning

The first attempt cooked the titanium a little bit. I'm going to try machining down the tool so it doesn't contact the whole inside diameter of the tube and feed it slower.

Tube Block With Drill Bushings

CAM

Op 1

Op 2

Parts!

Op 1

Op 2