Screwdrivers Project

---

This hands-on project involved crafting two functional screwdrivers using distinct manufacturing methods. The first was a Phillips head screwdriver featuring a steel shank encased in an injection-molded plastic handle. The second was a flathead screwdriver combining a drop-forged and hand-shaped steel blade with a cast aluminum handle. This endeavor tested both manual machining skills and adaptability to various fabrication techniques, challenging my understanding of material behavior, tool setup, and process flow. 

The screwdriver project highlighted how different manufacturing processes impact time, complexity, and outcomes. The injection-molded handle was efficient and straightforward, and could typically be completed in under 45 minutes. Conversely, the drop-forged aluminum screwdriver presented more challenges, particularly with the knurling process. I underestimated its sensitivity; minor errors necessitated complete redos, consuming valuable time. I looked into how many times I could redo the knurling and found some helpful advice:

• The finished aluminum handle was 1.00 inch in diameter and 4.60 inches long, but to make room for rework, the raw material would need to be larger. If we plan for four or five chances to re-knurl and reface the handle, then extra material is essential.

• A solid rule of thumb is to leave about 0.010 to 0.020 inches of extra diameter per refacing cycle to keep the surface clean and within tolerance [27]. After five cycles, that meant we would need up to 0.100 inches extra, so choosing aluminum bar stock that was 1.125 inches in diameter (rounding up to a common orderable size) would be ideal.

• We would also need to allow extra length. Each time we reface the ends, we lose material. By adding about 0.50 to 0.75 inches, we would need to start with a bar that is around 5.25 inches long, to give us enough room to hold onto the part securely and still hit the final spec [28].

Note: We were not provided with the dimensions of the raw stock, and it wasn't until after machining and while I was writing this that I thought about the need for the raw stock dimensions. Another lesson learned: know where you are starting.

• Oversize Raw Stock: If you have the option, select a raw stock aluminum bar that is oversized so you can redo the knurling process. 

• Measure Your Raw Stock: Knowing how much extra material you have available will help you determine how many times you can reface and re-knurl, if needed,

• Start Early: Begin the knurling process as soon as possible. It's time-consuming and technique-sensitive.
   
• Seek Assistance: Don't hesitate to ask lab staff and instructors for help. Early questions can prevent repeated work or part damage.
   
• Patience with Knurling: You get multiple tries to do the knurling, so leave time to reface your handle if you don't get the knurling right. Keep trying! You've hopefully already oversized the aluninum round stock to allow for this.
   
• Stay Ahead: Maintain a proactive schedule, focus on details, and utilize available support to ensure project success.

This project relied on EMEC (Educational Manufacturing and Engineering Center) methods to fabricate two screwdrivers. These techniques provided valuable hands-on experience but aren't optimized for speed or scalability. Once I analyzed the numbers, it became evident how inefficient these methods would be in a real-world production setting.

EMEC Injection-Molded Phillips Screwdriver

• EMEC Cost per Unit: $22.68
• EMEC Production Time: 0.75 hours per unit
• Time to Produce 10,000 EMEC Units: 7,500 hours

EMEC Aluminum Flathead Screwdriver

• EMEC Cost per Unit: $443.54
• EMEC Production Time: 16.6 hours per unit
• Time to Produce 10,000 EMEC Units: 166,600 hours

To put that in perspective, producing 10,000 flathead screwdrivers using EMEC methods would take nearly 19 years of nonstop labor from one person working 24/7. Even the simpler Phillips driver would require over 10 months of full-time effort from a single operator.

These comparisons underscore a critical point: efficiency isn't just beneficial, it's absolutely essential. Without modern manufacturing tools, automation, and streamlined processes, producing the EMEC screwdrivers at a scale of 10,000 units is practically unfeasible.

Machining and Forming

To bring production costs and time down to industry standards, each part of the build would need to be modernized using proven manufacturing systems.

Phillips Screwdriver

• Shank Preparation
  Time per unit: 0 minutes
  Pre-formed shanks are purchased and ready to go, so no additional shaping is needed.
   
• Insert Molding
  Time per unit: ~1.2 minutes
  The shank is placed automatically in the mold while molten plastic is injected around it in a single, streamlined operation [34].
   
• Handle Trimming & Cleanup
  Time per unit: ~0.5 minutes
  Any flash is removed using robotic trimmers that leave a clean edge with no manual labor [35].

Flathead Screwdriver

• Shank Grinding & Shaping
  Time per unit: ~3.5 minutes
  CNC grinders remove material precisely and repeatably, fixing the inconsistency issues we had with manual grinding [36].
   
• Handle Die Casting
  Time per unit: ~1.5 minutes
  Instead of casting by hand, a high-pressure die casting process would produce parts quickly with tighter tolerances [37].
   
• Automated Knurling
  Time per unit: ~1.0 minute
  CNC lathes apply the knurl pattern with no risk of slipping, overrolling, or needing a redo [38].
   

Finishing

After machining, both screwdrivers would go through a quick and consistent finishing process to get them ready for reatil.

• Deburring
  Time per unit: ~0.5 minutes
  An automatic deburring head takes care of sharp edges [39].
   
• Polishing or Tumbling
  Time per unit: ~2.0 minutes
  Rotary tumblers or polishers add a uniform finish, removing casting or machining marks.
   
• Assembly
  - Phillips Screwdriver: ~1.5 minutes per unit
  - Flathead Screwdriver: ~2.0 minutes per unit
  Pneumatic jigs and fixtures help align and secure parts quickly with minimal effort.
   

Total Estimated Manufacturing Time per Screwdriver

• Phillips Screwdriver: Approximately 5.7 minutes per unit 
• Flathead Screwdriver: Approximately 10.5 minutes per unit

To really push efficiency even further, I would design custom fixtures that allow multiple screwdriver handles or shanks to be machined at the same time. For example, a knurling jig that holds four handles in a row could dramatically reduce cycle time and make better use of each machine pass. Similarly, molding or casting multiple handles in a single shot would minimize downtime and improve throughput.

Using automated tool changers on CNC machines would also make a major difference. These systems let the machine switch between drill bits, knurling wheels, or grinding tools without operator input. That keeps the workflow moving without delays, especially during multi-step operations like forming, trimming, and cleanup.

If the goal is to produce thousands of screwdrivers with consistent quality, these types of setups are mandatory. They reduce idle time, increase repeatability, and make large-scale production extremely practical.

To make one injection molded Phillips screwdriver using EMEC methods, the material cost was $3.58, and the production time was 0.75 hours.

Scaling that up to produce 10,000 EMEC injection molded Phillips screwdrivers would cost $35,800 in materials and take 7,500 hours of manufacturing time.

Now compare that to the mass production version. In bulk, the same screwdriver costs $3.00 in materials, lower by $0.58 because sand paper is no longer necessary. Production time is reduced significantly to just 5.7 minutes, or 0.095 hours per screwdriver.

At that rate, producing 10,000 units would cost $35,800 in materials and require only 950 hours of machine time.

That is a 16 percent reduction in material costs and an 87.3 percent cut in production time, saving 6,550 hours.

Insert molding, automated trimming, and bulk part purchasing all contribute to a faster, more affordable build. In mass production, the process becomes nicely refined.

The aluminum flathead screwdriver made in the EMEC shop used $21.08 in materials and took 16.6 hours to complete.

At 10,000 units, that adds up to $210,800 in materials and a total of 166,000 hours of production time.

With modern manufacturing, that same screwdriver costs $8.86 in materials and takes just 10.5 minutes, or 0.175 hours, to make.

That drops the time for 10,000 units from 166,000 hours to 1,750 hours.

That is a 98.9 percent reduction in time.

That means 164,250 hours saved, the equivalent of over 18 years of continuous work from one person.

Die casting, CNC grinding, and automated knurling are not just upgrades. They are the only way a product like this makes sense at scale.

It was not a requirement to compare labor costs associated these two manufacturing methods, however, I think that is a great comparison and I decided to take a look at it below. 

At the start of this project, I thought building a screwdriver   was just about machining parts and putting them together. But by the end, I realized it is actually a lesson in decision making. The injection molded Phillips screwdriver and the aluminum flathead screwdriver each took a very different path, and in doing so, they revealed something important about how products evolve from prototypes to scalable designs.

• Injection Molded Phillips Screwdriver
   
  • EMEC cost: $22.68
     
  • Mass production cost: $5.42
     
  • Savings per unit: $17.26
     
• Aluminum Flathead Screwdriver
   
  • EMEC cost: $443.46
     
  • Mass production cost: $7.46
     
  • Savings per unit: $436.00
     

Applying a standard 100 percent retail markup, which is commonly used to cover overhead and profit [26], the numbers become even more dramatic:

• EMEC Injection Molded Phillips: $22.68 × 2 = $45.36
   
• Mass Produced Phillips: $5.42 × 2 = $10.84
   
• EMEC Aluminum Flathead: $443.46 × 2 = $886.92
   
• Mass Produced Flathead: $7.46 × 2 = $14.92
   

Now compare those prices to real world products. The Husky #2 Phillips screwdriver at Home Depot sells for $6.50 [32], and the Team EDS flathead screwdriver with a knurled aluminum handle retails for $18.98 [33].

My mass produced versions are close to, or cheaper than, these retail tools. The EMEC versions, though, are not even in the same universe!

This is the kind of insight you only get when you scale. The aluminum flathead screwdriver was the most technical and time intensive build. It looks great and taught me a lot about machining and precision, but without process refinement, it is not realistic for manufacturing. The injection molded Phillips screwdriver, on the other hand, was efficient, balanced, and production ready. It showed how a simpler design can deliver better results when matched with the right tools and strategy.

These two manufacturing paths tell very different stories. One reflects craftsmanship and complexity. The other reflects clarity and efficiency. Together, they revealed how real products evolve, not by staying in the shop, but by moving forward through smart decisions, lean processes, and intentional design.