To improve the serviceability of the tail subframe I sectioned the 1/2” tube in two places. However, the smallest tube connector I could find was for 1” tube. I considered machining them, but I need four and each requires multiple lathe and mill / rotary table operations. Given that my standards are much higher than my machining skills, I decided to have them CNC’d. This allowed me to add some nice features; (1) a chamfer for the weld, (2) boring of the section that inserts into the tube to reduce weight, and (3) tolerances that capture the nut which removes the need for a wrench.
Two symmetrical tube connectors
I’ve used Hubs to CNC parts in the past so I uploaded the CAD model and selected 4140 alloy, “as machined” finish, and economy offshore (23 business day delivery). `The prices below are for a single part (i.e., half of a set). As you can see, the unit economics for CNC machining is radically different than 3D printing or laser cutting.
Quantity Unit Price:
1 $107.21
2 $71.73
10 $22.35
1,000 $1.15
This is due to the need to generate the G-code for the first part and potentially the need to fabricate custom fixturing, which this part didn’t require. These unit economics influenced the design. I had considered an asymmetric design in which the half with the socket head cap screw was different than the half with the nut, but that would result in two different parts and half the quantity. Since there was only a small aesthetic difference for a hidden part, I went with a symmetrical design.
The screen shot below shows the pricing difference for 10 pieces (i.e., 5 pairs) for on/off shore and different lead times.
I’m very pleased with the quality
Chassis tube sectioned and tube connectors ready for welding.
The part geometry captures the nut so no tools are required on the back side