Modified Speed Square

Topics Covered
1. In a Nutshell
2. Cut Speed Square Using Chop Saw
3. Check for Squareness
4. Making Square
5. In Closing
6. Request
7. Related Links

Shown in the following photo is the speed square I modified.

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In a Nutshell
The modification process consisted of using a chop saw to reduce the size of the speed square, check the modified speed square for squareness, and then if necessary (I found it necessary) use a belt sander to square up the modified speed square.

Cut Speed Square Using Chop Saw
Speed squares are relatively inexpensive, especially if you pick them up at yard sales or flea markets. Therefore, I had no problem taking a chop saw to one of the speed squares I currently own.

For starters, I put a metal cutting blade on my chop saw. Next, I positioned the speed square on a piece of MDF as shown in the photo below, and made my first cut on the speed square. One cut down, one to go.

The MDF is required because of the ribbing on one leg of the speed square; it would not sit flat on the chop saw tabletop, and the heat generated by cutting thru the metal speed square would not be good for the chop saw plastic table insert.

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With the speed square repositioned as shown in the photo below, I made the final resizing cut on the speed square.

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Check for Squareness
With the speed square cut to my desired size (2-7/8” x 3-1/2”), I next checked the speed square for squareness.

Draw a line (Line #1) as shown in the following photo. I drew the line and shifted the modified speed square away from the drawn line (Line #1), so you could see the penciled line.

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Next, rotate the modified speed square as shown in the photo below and draw a second line (Line #2). The line labeled “Line #1” in the above photo is also shown in the photo below. In the photo below, the two lines #1 and #2 should be parallel to one another, but they are not. Since the two lines #1 and #2 are not parallel to one another, the modified speed square is not square.

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Making Square
To square the modified speed square, the end of the speed square leg (with the lettering “ALUMINUM ALLOY SQUARE”) opposite the end with the gap between lines #1 & #2 needs to be ground. I used the belt sander on my combination belt and disc sander for this task.

During the grinding process, I worked at grinding the most metal at the end opposite the gap between lines #1 and #2. At the same time, I worked at grinding less and less as I approached the end with the gap between lines #1 and #2.

In the sketch below, the area to be grounded away is shown shaded in blue. I find the sketch below helpful in visualizing why the bulk of the grounding is required at the end of the leg opposite the leg end with the gap between the lines #1 and #2.

SKETCH #1

After grinding the shaded blue area away to the red line shown above, leg #1 and leg #2 will be at a right angle to one another and the modified speed square will be square.

Grinding the blue area shown above to square up the modified speed square is a trial and error process. Grind on the belt sander and draw lines #3 and #4 shown below, if the two lines are parallel then your modified speed square is square. If lines #3 and #4 are not parallel then grind again and draw the two lines shown below again, it took me about six tries at grinding and drawing lines before I squared up the modified speed square. That might sound like a lot of trouble, but it went reasonably fast.

The photo below shows lines #3 and #4 drawn after the two legs of the modified speed square have been ground square to one another. Line #3 was drawn with the modified speed square on the left side of line #3, and line #4 was drawn with the modified speed square on the right side of line #4. Now, lines #3 and #4 are parallel to one another, and the modified speed square is good to go.

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In Closing
Out of necessity, I made the modified speed square shown above. I had a situation whereby I needed to measure for square between two wood members and a standard size speed square was too large. Therefore, I cut a standard size speed square down to the size I needed.

One final thought, any time I can take my existing tools and make a new tool that makes for a fulfilling day in my shop. Bet you feel the same way.

Request
If you enjoyed this post, I would be very grateful if you would share it by email with a friend, or on Google+, and/or Facebook. While I am being needy, would you give me a “Like” on my Facebook page (Woodworking with AJO)? My Facebook page “Like” button is on the right side of this page, or you can click on the link shown below for my Facebook page. Thanks a bunch.

Woodworking with AJO | Facebook

Until next time, Take care
AL

Related Links:
▶ Martin Doyle’s Modified Square – YouTube
Swanson Tool SO101 7-inch Speed Square – Amazon.com
How To Use A Speed Square: Five Jobs for This Classic Tool – Popular Mechanics
Speed square – Wikipedia, the free encyclopedia

 

 

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