# Circular Square, What is it and Where to Use it



## 75Plus (Mar 23, 2012)

I know that the name is right up there with "Left Handed Monkey Wrench" and "Striped Paint" however it is a handy tool that can be made from scrap. It is used in determining horizontal/vertical relationships. Pictures to follow.

Starting with a piece pipe or round stock approx. 1" in diameter turn a 3" length so that it is true and smooth. Carefully face the end. If using solid stock drill a shallow hole in the center to ensure that the tool will set level when in use. Part off and chamfer the end to identify it as the top. Only one end is used.

OK you have made it so what do you do with it?  A recent post here prompted me to post this so I will use it to illustrate. Here is the thread:

http://www.hobby-machinist.com/showthread.php/5696-quot-Tramming-quot-or-squaring-a-drill-press

This is how the "Circular Square" is used. 

I wanted to determine if the table on a small drill press was level with the quill or "in tram". I first placed a piece of known straight round stock in the chuck. I then placed the "Circular Square" behind it and found that the table appeared to be level back to front. See picture # 1. I then placed it in front of the test piece and left a small gap so I could compare the width of the gap top to bottom. It appeared the same. See picture #2. Next I placed the CS to the left of the test piece and found that the table was low on the left side. See pic. #3. Just to be sure I moved the CS to the right side and found the same. See pic. #4. I leveled the table with the CS in place and checked both sides. The table is now in tram. See pic.# 5 & 6.

While in my tool box getting a wrench to adjust the table I noticed a bright, new 17mm deep socket. That peeked my curiosity so I grabbed and tried it as a CS. I then realized I had the tool needed for this job. I just had not made the mental connection. See pic. #7

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Another use for this tool is to ensure a part is vertical in a vice. It can be used in place of a regular square which may fall into the space between the jaws when the work piece is wider than the square.

Joe


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## 8ntsane (Mar 23, 2012)

Joe 
I like that idea, simple, easy to use, and as you say can be used on a vise to check square of the work piece.

I dont know why I didnt think of that myself. 
Thanks for sharing that tip


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## AR1911 (Mar 23, 2012)

I have 3 cylinder squares. They are piston pins from big truck engines. They are hardened, ground to a fine tolerance, and square beyond my ability to measure. 
Mine are about 2" dia X 4" length. Very handy


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## Philco (Mar 28, 2012)

I'm with AR1911, I find that discarded parts out of engines make very precise set up tools for the home shop machinist, such as piston pins, hydraulic lifters, oil pump gears. I also find automatic transmission parts can be a good source. The best thing about them is most automotive type machine shops would be happy to give you some before they haul it off to the scrap yard. I also find ball bearing races are precision ground. I hope this will help someone keep the cost of set up tooling down! PHILCo.


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## GK1918 (Mar 28, 2012)

mine are Detroit diesel wrist pins


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## R.G. (Mar 28, 2012)

!! Diesel engine parts !!

We have a local diesel repair shop!

Thanks !!


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## jpfabricator (Aug 29, 2013)

could a Deep socket that is checked first do the same thing?


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