Expert: Mark H. Miller - 6/23/2011

Question
I'm having trouble understanding how no sag spring should be measured since it comes with a significant crown on it.  I've heard that it should be cut shorter than the space that it is going to be installed into (usually said to be about 3 inches for a large chair) to presumably remove most (all?) of this crown by stretching.  If I push the spring down on a flat surface first and measure and cut it 2 or three inches less than the opening I'm having great difficulty stretching it that additional 2 or three inches.  Could it be that I should only be stretching it enough to remove most of the crown?  Is there a standard way to calculate, say, the number of loops per inch/foot of opening?  It seems like the what may be 3 inches for a 25 in opening could be significantly less for a 16 in opening?

Answer
The spring should be about 3 inches less than the distance between the clips.  Cut the spring in the center of a loop - that will leave a hook which will prevent the spring from sliding out of the clip.  Hook the spring into the clip that is at the back of the chair,  close that rear clip and put all nails into the clip to secure it completely.  Take a piece of about 30 inches of spring twine and very securely wrap that around the second loop going back from the front of the spring.  There should be a double twine hanging off of the spring.  If you are right handed wrap that double twine several times around the palm of your hand very securely.  With your left hand hold the frame and then stretch the spring into the clip.  Doing this will take considerable strength - if it doesn't the spring is too long.  Immediately hammer the clip shut and put the nails in to permanently secure the spring into the clip.  Do this to one spring at a time.  Installing no-sag springs has the potential to cause very serious injury - be extremely careful.  

There will be a crown,  you can not stretch a no-sag spring so that there is no crown.  That is the reason I advised you to build a lower ledge, so that the crown will be even with the top of the frame.

Good luck  have fun,  but be extremely careful.

Mark Miller.