Real Numeracy

A simple jig lets you make a straight cut on a curved piece

by George Taniwaki

The instructions below show how to create a jig to make a straight cut using a band saw on an irregularly shaped object. The jig is made of modeling clay and is attached with duct tape to a crosscut sled that rides in the miter slot of the band saw.

An important warning. You should not use modeling clay and duct tape to make a jig for a table saw or miter saw. Kickback forces can damage the part or cause injury to you or bystanders.

For this particular project, the jig will hold the parabolic reflector for a recessed light fixture. The reflector is made of plastic with a metalized coating. The reflector is about 100mm (4") in diameter at the bottom, 75mm (3") in diameter at the top, and 125mm (5") tall. I want to cut 25mm (1") off the bottom. (An explanation of why I want to do this at the end of the blog post.)

Make a crosscut sled

The first step in making the jig is to make a reusable crosscut sled. The sled consists of two pieces. The bed is made from 6mm (1/4") plywood. The back is made from 19mm (3/4") plywood that is tall enough to hold any piece that will fed through the band saw. Note the notch in the back to allow the sled to fit under the band saw work light.

The crosscut sled should then be attached to a runner that will fit in the miter slot of the band saw. I simply attached mine to the miter gauge using bolts recessed into the back of the sled.

A band saw crosscut sled

Make a mold

An easy way to make a solid jig for an irregularly shaped object is to use modeling clay to make a mold. You can buy modeling clay at any hobby shop such as Michaels. To keep the modeling clay from sticking to the object, cover the object with thin plastic food wrap such as Glad cling wrap or lightly spray it with oil such as WD-40 to act as a release agent.

Soften the clay by working it in your hands. Press it against the object you want to fit on the crosscut sled. While still soft, add bits of modeling clay to the mold so that it fits squarely against the crosscut sled. Let the modeling clay cool to harden it.

Wrap the finished mold in plastic food wrap so it doesn’t stick to the part. If you only need to make a single cut, you can skip this step.

Modeling clay and the finished mold

Band saw setup

Attach the mold to the crosscut sled using strips of duct tape, aligning it so the line to cut is directly above the edge of the crosscut sled.

Place the object to be cut in the mold on the crosscut sled. Make sure the object is aligned to the band saw blade using a machinist square. Then attach the object to the mold using strips of duct tape. Start up the band saw and slowly push the crosscut sled through.

Aligning the object to the blade (left); Preparing the push the crosscut bed through the band saw (right)

* * * *

The need for this jig arose because I wanted to replace the GX24 compact fluorescent light bulbs (four pin base) in the kitchen with standard E26 LED bulbs (screw-in base). We remodeled the kitchen in 2008. Back then it was obvious incandescent bulbs were going to become obsolete soon, so we installed ten recessed light fixtures with state-of-the-art CFL bulbs. Now, just over 10 years later, CFLs are obsolete. The problem with GX24 bulbs is that the ballast is part of the fixture, not the bulb. Unlike office lights, kitchen lights are flipped on and off all day long and the ballast eventually burns out with no easy way to replace it.

Replacing the bulbs requires removing the ballast and adding a GX24 to E26 adapter.  The adapter is about an inch long, which is why we need to cut an inch off the reflectors.

LED bulbs should have a life of 20,000 hours. So hopefully we won’t have ever replace the bulbs again. Technology moves too fast for me.

Yard signs that worked (from Kennebec Journal, Sep 2018)

by George Taniwaki

In a July 2019 blog post, I discussed the use of billboards to help publicize your need for a kidney donor. If you can’t afford a billboard, smaller yard signs are a good alternative if you have legal access to to the right-of-way next to a busy road , specifically one with lots of slow moving traffic.

The picture at the top of this blog post shows an excellent example of an effective yard sign. They were designed and installed by Krystal Reardon, a nurse and kidney patient in Augusta, Maine. She has six yard signs, all with black text on a blue background. The signs read “I require a life-saving transplant”, “Kidney”, “Donor”, “Needed”, “Would you consider”, “Ask me how (207) 518-0000 Kidney0000@gmail.com”. The first and last signs are hand painted, while the other four signs are stenciled. Her story was carried by multiple news outlets including Kennebec Journal (Sep 2018) and People (Sep 2018).

Her signs generated a remarkable 30 responses from strangers who have offered to get tested (Fox News, Sep 2018). She received a transplant shortly thereafter. Now she is helping other kidney patients use the same technique to find their own donors. You can see her handiwork for Kenneth Edwards and Rachel LaJoie in the second row of the photographs below.

Seven examples of kidney campaign yard signs in the news

First row: Angela (from CTV News, Jul 2016), Dan (from WLWT, Aug 2015)

Second row: Joan (from KidneyQuest on Twitter), Kenneth and Rachel (from Press Herald, Mar 2019)

Third row: Mark (from Union Leader, May 2019), Jim (from Café Mom, Jan 2014)

Since the signs are small and most people who see it will be driving fast, you cannot put a lot of text on it. All of the yard signs have the following two features:

1. Headline or call to action – Kidney needed or donor wanted

2. Contact information – phone number, email address, or website

One option to increase awareness and to tell a longer story is to use multiple signs spaced several feet apart, like Ms Reardon did for herself and for her mentees.

Another option, which works in an area that receives plenty of snow and stays cold is to build a seven-foot snow sculpture of a kidney (see last picture in the third row) and plop your sign next to it.

Media attention

As mentioned in my blog post on billboards, another way to expand your search is to get your yard signs covered by the local newspaper or television news. All of the yard signs shown in this blog post were found on news websites.