Screwdriver
The screwdriver project introduced me to knurling on the manual lathe, and CNC turning.
The biggest takeaway was seeing how much setup and process choice affect the final part. Knurling taught me that consistent results come down to consistent pressure and feed, not just cranking the tool in and hoping for the best; a rushed pass leaves an uneven pattern that's obvious the moment you run your hand over it.
Running the CNC turning operation, even without writing the CAM myself, showed me the other side of that same lesson: how much thought has to go into a program before the machine ever touches material. Watching a process that's dialed in versus one that isn't made it clear that the setup work is where the real machining happens, not at the button press.
Overall, this project reinforced that machining quality isn't really about any single skill, it's about paying attention at every step, whether that's a manual process you're controlling by feel or a CNC process you're trusting to run correctly.
Screw Driver Cost Estimate:
RAW STOCK
Aluminum:
~ 22in^3 per screw driver
0.0979 lb/in^3 -density of Al
~2lb per screwdriver
~ 2.50 $/lb
~ $5 of al per screw driver
01 Tool Steel:
6" x 0.375" dia
~ $3.40 of rod per screwdriver
~ $8.40 of stock per screwdriver
LABOR
hrs spent: 10
$26.95 hrly wage for a Co machinist
$269.50 of labor per screwdriver
$277.90 per screwdriver
Potential Improvements
The current process utilizes the CNC mill for the majority of the turning processes however I think all could be done on the CNC mill. The forging process should also be automated.
changes:
1. knurling in the CNC mill
2. facing in the CNC mill
3. Employ and automated forging system where the rod on the blank is cut to length then is induction heated and fed into the forge
4. CNC grinding for the screwdriver tip and shank to ensure accurate fit in screws
EMEC vs Automated Processs
EMEC Costs
1 screwdriver:
$277.90
10,000 screwdrivers:
$2,779,000
hrs per screwdriver:
10hrs
hrs per 10,000 screwdrivers
100,000hrs
Automated costs
1 screwdriver:
~ $15 (stock + electricity + tooling)
10,000 screwdrivers:
~ $150,000
hrs per screw driver:
1 hr
hrs per 10,000 screwdrivers:
10,000 hrs