How to get a frame squared at right angles

[Madhu Sudhan]

Hi 

I have a basic question about framing. I framed a rectangular table top using 2 X 4. I used pocket holes for the joints. I found that the angles were not perfectly squared after joining all the four sides. Sizes of the opposite were exactly the same. If I loosen the screws the frame is a perfect square, however when I tighten the joints it is not squared. Is there a technique I can use to ensure that I have the frame squared perfectly? 

[Ken Darga]

1. Insure your cuts are at 90 degrees---

this is necessary for accuracy.

2.  Use a rafter/framing square to check your progress---

before, during and after your tasks at hand.

Get a good one.  A thick aluminum one is the way to go.

A 12" square is also very useful in the shop.

3.  Obtain an accurate "combination square".

Most of the cheap home center squares are not accurate.

(I've found some to be off by 1/32 - 1/16 on 12").

Look for line markings to be very thin.

(My Starrett machinist measuring tools very thin lines are .005" wide).

Before purchasing a square, check it out for accuracy at the store, before you buy it.

I check out my squares for accuracy, before proceeding with a project.

( They may have inadvertently gotten dropped, and become out-of-square. 

I want my squares "dead square" with no margin of inaccuracy so I strive for perfect methods to determine their accuracy.

NOTE

I use a "marking knife" for making accurate cut-lines.

(A pencil line width varies with the type of pencil and the lead thickness).

TIP

Make a "dry-fit" before installing permanent fasteners.

Measure across the diagonals---if it's square, the measurements will be the same.

There's a old saying in woodworking---

measure twice, cut once.

[Madhu Sudhan]

Thank you very much for your advice. Will try these steps