Assignment 2/Part 1 of 2: Fastening and Attaching

We learned four methods of fastening and attaching, all of which we plan to use on our windlass!  Practicing these methods gave us a very concrete understanding of their benefits and disadvantages.


1.  Piano Wiring involves drilling a hole into your material and putting piano wires through them.  The screw used to drill the whole varies in size so that you may vary your fit (running or press).

• Function: Attaches separate parts together in numerous ways, limited only by your objective, materials, and creativity.

• Advantages:  

1. The piano wire is relatively strong, so it will hold your parts in place, depending on the force applied to the wired area. 
2. Not permanent, so you can remove the wire and separate your parts, if need be.
3. Several pieces can be drilled together like a hinge, allowing mobility.

• Disadvantages: 

1. Drilling down a thin piece of delrin requires a lot of precision (that was almost impossible to achieve without luck!).  The screw and your piece must be properly aligned.  Anything in the way could potentially bend the screw and drill in the wrong direction, instead of drilling through it.  
2. Drilling down a thin piece of delrin could potentially make your part prone to breakage. 
3. If you do not drill carefully, you run the risk of damaging your part to the point that it is unusable.
4. The piano wire must be completely straight, or it will not go down the drilled hole.
5. If the screw is not long enough, or if your part is too long, the drill press will not be able to run down the entire desired length of the part.  If possible, you can turn your part around the opposite side but there is a very low chance your two drilled paths will meet.

2.  Pegs & Notches involve cutting out your parts so they fit together like legos/puzzles. You can  vary the size of your notch and peg depending on your desired fit (press, running, or in between).

• Function:  Attaches separate parts together perpendicularly.  

• Advantages:

1. Not permanent, so you can take your attached parts apart. (Try saying "attached parts apart" really fast 10 times! xD)
2. Several parts can be attached together.
3. Depending on your material, you can sand down the peg or the notch to adjust your fit.

• Disadvantages:

1. Several iterations are required to get your desired fit, which can be wasteful of time and material.
2. Your calculations may be perfect, but the laser cutter is not and may cut your material in a less than desirable way. 
3. If your material is even slightly warped, there is a higher chance you will not achieve your desired fit.
4. Does not allow for mobility where the parts are connected.

Tolerance and Measurements using a caliper*: (For Peg and Notch Set #1)

Peg width: ~0.124in 

Loose notch width: ~0.164in

Tight notch width: ~0.1245in

SolidWorks vs. Our Measurement using a caliper*:  (For Notch Set #2)

SolidWorks measurement for notch #1: ~0.135in

Our measurement for notch #1: ~0.141in

SolidWorks measurement for notch #2: ~0.125in

Our measurement for notch #2: ~0.134in

SolidWorks measurement for notch #3: ~0.115in

Our measurements for notch #3: ~0.112in

3.  Bushings are hollow cylindrical pieces of material with variable height, inner radius, and outer radius.  This allows for adjustment depending on your desired fit (tight, running, or in between).

• Function: Holds parts in place on the rods.

• Advantages:

1. Can be moved any time with variable force to desired place on rod.

• Disadvantages:

1. Same disadvantages as those for pegs and notches (1-3).

Tolerance and Measurements using a caliper*:

(Each of the following measurements is an average of three trials)

Rod diameter: ~0.25in 

Tight bushing inner diameter: ~0.256in

Loose bushing inner diameter: ~0.26in

Running bushing inner diameter: ~0.262in

4.  Heat Staking involves melting materials together.

• Function: Attaches parts by melting them.

• Advantages:

1. Melting pieces together allows for a strong attachment.
2. Does not require perfectly calculated precision or rely on luck and therefore, simplest of the four methods.

• Disadvantages:

1. Attachment is permanent.
2. Different materials may not melt together and create a strong attachment since their melting rates may vary at a fixed temperature.
3. Forms a round bump where the heat is applied and destabilizes the structure if the round top is touching the surface your structure stands on.
4. Difficult to heat stake parts that that do not fit in the circular opening of the heat staking machine.

*We found that caliper measurements are delicate and change easily with variable force used to separate the measuring bars on the instrument.

Laser printing adds to precise measurement error.