Alright, maybe it's not the most glamorous topic, but there's a real need for this project.
Sometimes replacement parts are not available anywhere. A problem came up for me recently, and I was able to create the part using AutoDesk Inventor and 3-d printing technology.
The Porter Cable 557 type 1 biscuit joiner uses plastic parts for the key fence hinges. These parts are prone to breakage and the supply of spare parts is exhausted. Any web search for "part 151" will turn up only part suppliers who report that the part is no longer available, and forum posts from people who are trying to find one.
For the lack of a $1 part, a $200 tool is rendered unusable.
Here's how I learned all this: Not too long ago, I picked up a biscuit joiner cheap on eBay. The ad said that there was one broken plastic part. Not realizing that it was a critical part, I bought the joiner. After a month of fruitless searching for a replacement part, I realized I would have to make my own or junk the tool.
Step 1: The Tool
I needed a biscuit joiner for my shop, but not badly enough to feel justified paying the full new price. Eventually this bargain turned up on eBay. The text said there was a broken pivot piece, but that the replacement part is easy to change. That's all true enough *if* you can get that replacement part. However, it turns out that the part is simply not available.
At this point, it was either scrap the tool, or come up with my own pivot piece.
Step 2: Measuring the Part
The first photo shows the broken part. The damage might not look too bad in this photo, but in practice it leaves the joiner fence loose and wobbly. The tool is unusable as is.
The first step was to get a pair of calipers and take all the measurements I could.
Step 3: Designing the Part in AutoDesk Inventor.
The next step was a quick session with AutoDesk Inventor. It was surprisingly easy. The entire project could serve as a beginner's tutorial for the software. A copy of the ipt file is enclosed.
Step 4: Generate and Upload .stl File
AutoDesk Inventor can generate an stl file, which is the format used by most CAM software. Not having my own 3-d printer, I uploaded it to Shapeways.com. Shapeways allows you to print an object in a variety of materials, ranging from plain white plastic to stainless steel. I opted for the plastic since it's the cheapest.
The stl file is included here. The model is available at the AutoDesk 123D gallery. You can also access the project directly at Shapeways, and order your own copy shortly.
As an aside, there's a plugin for Sketchup (http://sourceforge.net/projects/stl4su/) which allows you to import stl files into Sketchup. I find this a useful way to double-check an stl file.
Step 5: The Finished Part
Two weeks later, this arrived in the mail.
Step 6: The Part Is Installed
The piece was a perfect fit. I had expected to need to make refinements on my prototype, but the very first version fit the joiner perfectly right out of the box.