Posts

Precise Cutting of Heavy Brass Tube

Image
I had a need to make bearings out of a brass tube and each piece had to be within a thousandth of spec. I had a brainstorm to use my ShopBot CNC as a measuring device and came up with this contraption.

The rod is 1/2" diameter with a 1/4" inside diameter.
The multitool is level and square to the machine and locked to a piece of 2x4 by landscaping tape and hot glue. Not exactly a permanent fixture but good enough for the job.
To actually cut the rod, I used the keyboard function, "D" set at 0.001" and set the zero position within 0.02" of the multitool blade. Then I just arrow keyed the tube into the rod with the RPM's at 6,000. The wire runs up the tube a short distance and catches the rings as they separate.
To repeat, I move Y to zero, zero Z and lowered the Z to the desired depth for the next cut.
I made a couple of test cuts to calculate kerf and see how good the cut quality was and then subsequent cuts were good. I needed 12 at 0.250" and 4…

Copying a Profile Using Liquid Urethane Foam

Image
I needed to copy the basic shape of a part of my car so I could work with it without damaging the original. It's part of the rollbar which is covered in leather. If I had a fancy scanner and 3D printer, I could have easily done this. Instead, I did it the manual way using aluminum foil and liquid urethane foam.

Liquid urethane foam comes in two parts that are mixed together in equal measures. The amount of rise from the foam is dependent on the weight per cubic foot. The range of densities goes from a very light half pound per cubic foot to a very hard and dense sixteen pounds per cubic foot and even more. The more dense the foam, the harder it is and the more abuse it will take to damage it.

Once mixed, the foam rises very fast, in the order of a few minutes, and then sets to a very hard material in about twenty minutes total. While it is rising, the foam itself exerts very little force on the material constraining it if it is allowed room to rise completely. Constraining the fo…

Four Sided Machining With an Indexer

Image
I'm working on a project that requires hundreds of precisely machined components. Most of them can be produced easily from sheet stock or scrap lumber using 2D cutting methods. A few I've made by hand as they were just a one off.

One part I need for the project, a piece about nine inches by three inches by one inch thick, is machined on four sides. The shape is a trapezoid, or more correctly, a parallelogram with two sides offset by six degrees. Two nearly vertical slices chopped out of one side are also offset by six degrees. Various holes are drilled for pegs and other things. It's also 3D shaped on the top and bottom (three inch sides).


The problem with multi-side machining is registration. A part is accurately registered if it is placed on the machining bed exactly in the place it should be. Knowing where the part is physically located is critical when attempting to machine it. The machining tool has no idea what is where. It only knows what to do. If the part isn'…

First Day at IO 2019

Image
This picture pretty much sums up my first day at IO 2019:
Why? Because I brought these back to the hotel. The capsule is a headache killer and the large circular one is a Tums. So IO day one was pretty smooth, no headache and the food didn't cause me heartburn.

Great sessions and information. Going to take a while to digest it all.

Inside IO:

Funny Story

Image
I recently went through the PreCheck line at an airport and instead of the usual thirty second security screening, they singled me out because they wanted to check my nuts. The officer implied they exceeded tolerance and wanted to check my "bag". Naturally, I complied like any citizen would and when the officer was satisfied that my nuts, although excessive, were no threat to the flying safety of the general public, he left me with my nuts on the examination table without so much as a goodbye.


PVC Schedule 40 Flexible Pipe

Image
Anyone who has had to use numerous fittings to connect two pieces of PVC pipe will love the new Schedule 40 flexible PVC pipe. There are a lot of really great reasons to use this innovation in PVC piping:

1. It's virtually unbreakable. Unlike rigid PVC pipe, flexible pipe can withstand a lot of tortue before failing.

2. Instead of using numerous fittings to connect two pipes together, flexible pipe can be connected with nothing more than standard couplings.

3. Water will flow better through a complex join between pipes using flexible PVC since there are no sharp bends like elbows.

4. Even though flexible PVC is more expensive by the foot, it can be cheaper to use since the installation of this material is far simpler since fewer fittings are required.

5. Less fittings means less chance for mistakes and leaks.

The only drawback to flexible PVC that I can see is that it costs more per linear foot than rigid PVC.

Some pictures of this material in use:

Home Depot sells this stuff onli…

Zip Code Boundary Maps

In 2005, I wrote one of my first custom mapping projects using the recently released Google Maps API. It was a fairly crude map that used the Census Tiger ZCTA's (Zip Code Tabulation Area) to display a representation of a Zip Code area. Matt Cutts, at the time, a major player at Google in search, wrote a blog post called "Fun with Zip Codes" that caused my site to get an average of 70,000 unique visitors a day for about a week.

The traffic that Matt's blog post caused made me consider that there could be a market for this type of site so I looked deeper into the issue and learned a number of interesting things.

The most important thing I learned was that Zip Codes are not areas. They are delivery routes. The USPS draws these delivery routes based on the efficient delivery of mail and nothing else. They can cross city, county and even state lines if it means the mail gets delivered efficiently.

Not every address in the US has a Zip Code. This is not obvious for people…