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Old 08-28-2014, 07:46 PM
Evan G Evan G is offline
 
Join Date: Jan 2014
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Default All squared up - setting square to 1 / 1000th over 30 inches

I was having trouble setting up the square accurately enough using an empire speed square. The speed square is 1 foot by 1 foot. After setting up my EZ square, the angle was usually a little bit acute, and over 30 inches, it might be off by 1/16 to 3/16th.

I just made a jig that seems to work to get my cut piece to within a few thousands of an inch over a 30 inch piece. The jig is just a piece of 1/2 inch plywood that is 21" x 30". I screwed a squaring board to the plywood inset from the long edge make the square. To use it, you place the ez-square (with handle) along the 21" edge of the plywood, and bring the track up against the squaring board, then tighten. The squaring board I used was 1.5" x 2.5" by 30". I wanted it pretty rigid, and that was in the scrap pile.

In order to get this jig perfectly square, you need to test it, and adjust. I followed the instructions in this video by William Ng. The video is for setting up and adjusting a sled, but I followed the same procedure with my jig and the ez-square. After adjusting a few times, I did the test, and it came out to within a thousands of an inch over 30 inches.

The procedure is much easier to do than to describe in words, and it would be worthwhile to watch the video if this is confusing. The video is long, but very clear. The procedure goes as follows. (1) Attach the squaring board with just two screws (one on either end), and set your ez-square using the jig (2) Get a rectangular test board. (3) Mark one of the longer sides of the test board, and trim that edge using your ez-square (4) Rotate test board 90 degrees, and trim the next side (5) Repeat until you have trimmed each edge once (6) Rotate again and put the square to the test board so that the ez-track is on the side with the first cut (the one that you marked in step 3), then trim off a piece off about an inch wide. (7) Measure the width of the top and bottom edge of the trimmed piece. (8) Take the difference between these measurements, divide by 4. That is how far off you are over the length of this test strip. Divide that number by the length of the test strip, and multiply by the distance between the screws in your jig. That is how far you need to move one edge of the squaring board on your jig. You can conveniently do this with some feeler gauges or a micrometer. I used a feeler gauge set as described in the video. Now that your jig is adjusted to be square, repeat the test procedure and adjust as necessary.

One thing that I found helpful, is if your squaring board is not perfectly flat, set it up so that the bow is such that the top and bottom of the squaring board contact the ez-track. If it contacts in the middle and there is any gap at the top and bottom, you will never be able to set the square repeatably.
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Old 08-29-2014, 02:00 AM
Goblu Goblu is offline
 
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Very cool that you did this, Evan. Amazing results.

Could you post a picture? I'm having a hard time visualizing how the two board go together, with a "screw at each end" and what is being inset. Are they at right angles? I did watch the video, but still couldn't figure that part out.

Thanks for telling us about this jig.
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Old 08-29-2014, 12:00 PM
Evan G Evan G is offline
 
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Katie,

Here are some pics.

The first is the jig. The second shows how it is used to set up the square. The third shows the two screws coming in from the back side. These are at either end of the long squaring board. When you remove one screw and pivot the board to adjust it, the longer length of this board makes movement at one end result in a very small change to the angle of the square. Now that it is set, I should add a bunch more screws.

Adjusting it really is an identical procedure to the video, but just using this squaring jig instead of a table saw sled.
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Old 08-29-2014, 12:41 PM
bumpnstump bumpnstump is offline
 
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Evan,
great write up and explanation! Thanks for taking the time to share.

One quick mod that might make set-up/adjustment a bit quicker is to exchange one of the screws into the 2x4 for a threaded thru-stud w/a clamping knob. Scribe a small arc thru the plywood at the point of the clamping stud/knob; insert the threaded stud into the 2x4; poke the threaded stud thru the arc; clamp in place w/the knob. Eliminates multiple screws and allows for easier recalibration, should it be necessary.
Just a thought.......
Rick
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Old 08-29-2014, 02:49 PM
Goblu Goblu is offline
 
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Thank you, Evan. That's very clear now. I was visualizing something completely different. On my to-do list. I imagine could use this to set up other EZ tools that need squaring, too, like the ueg.
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Last edited by Goblu; 08-29-2014 at 02:53 PM.
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  #6  
Old 08-29-2014, 03:10 PM
Evan G Evan G is offline
 
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Thanks Rick,

That's a good idea for calibration. In my experience with Jigs like this, they will be good enough for my needs for many years. I want something that will stand up to plenty of abuse, so I'm going with lots of screws. If it needs calibration, I'll try your idea or play around with some other ideas.

One could come up with a similar jig that allowed for two or three angles and calibration by replacing the squaring board with a peg at the bottom and a block of wood at the top. Put a piece of threaded rod through the block of wood (with a t-nut) with the rod perpendicular to the track. Then, the track will contact the peg at the bottom and the threaded rod at the top. Then, rotate the threaded rod to adjust and add a lock nut to keep the setting. 1/8th of a turn of 1/4 20 is 6/1000th, so adjusting should be easy enough. You could just add a second block for 45 degrees.

Thinking things through a little further, if you had some dog holes in your Table, you could make little adjustable squaring blocks like I described above, and set them in specific dog holes. That would take up less space.

The real useful thing here is the procedure for testing the square and adjusting. I don't have a bridge or ez-one, but I imagine that it would be useful for setting that up square as well.

I can think of a similar test procedure with a right triangle for setting a 45oC cut. It involves making 2 45oC cuts, then a 90oC cut and testing the width of the test strip. However, that requires being able to make a perfect 90oC cut and only magnifies your error by a factor of 2. If anyone has a better procedure for that I'd be interested in knowing about it.
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Old 08-29-2014, 03:12 PM
Evan G Evan G is offline
 
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Katie,

What are the problems with the UEG being slightly out of square? I always just throw it together, and I seem to get consistent cuts.
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Old 08-29-2014, 04:46 PM
Goblu Goblu is offline
 
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I'm not sure, I've just seen at least one discussion of how to set it up and make it square. Maybe it was just a discussion from someone new, though. Mostly it seems easy.

But the track to the table/fence might be useful. I'd have to try it. I do square my track to the fence all the time using an empire speed square. This would be more accurate. I haven't done really long cuts due to space limitations with my current setup, but with my new table I will be able to. (MFTC).
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Old 09-01-2014, 02:10 PM
tomp913 tomp913 is offline
 
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I made something similar, posted it a while back, basically a strip of aluminum screwed to a piece of 3/4" Baltic plywood. The first photo shows how I laid out the perpendicular to the base of the fixture using a trammel to generate a perpendicular line as we were all shown in HS geometry- the long radius used to generate the perpendicular contributes to the accuracy. The second photo shows my check of the squareness of the strip to the base of the piece of plywood. In use, I butt the square to the plywood edge and rotate the track until it touches the side of the aluminum strip.

Tom
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  #10  
Old 09-12-2014, 01:36 AM
RJS1948 RJS1948 is offline
 
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Default Making Cuts 2 & 4 with the Jig

Please explain how you cut the rectangular piece of lumber with a 2 x 4 screwed onto the rectangular piece of lumber. I can visualize Cut 1, Laying the EZ square against plywood edge and the EZ track against the 2x4, but for cut number 2 how to you rotate the board and make cut when the 2x4 is now in the way of the EZ track. I understand the process but can't visualize how you rotate the plywood rectangular lumber and make cuts 2 and 4 as the 2x4 is in the way.... maybe the board is flipped over and you make all 4 cuts on the side w/out the 2x4. Kindly explain... Your response is appreciated...

Rob

Last edited by RJS1948; 09-12-2014 at 01:44 AM. Reason: context of last sentence needed changing
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