Hi,
Regarding nylon insert locking nut,
from the pictures of the this tutorial, lynxmotion.com/images/html/build114.htm
step 4.
How I do turn this nylon insert nut all the way down since there’s a nylon there preventing me from doing so ? It is almost impossible to turn it down.
Or I just don’t turn it all the way down and leave the this nut hanging at the tip of the screw ?
Cheers,
munchu
the nylon locking nut should tighten all the way down, fastening the servo tight. 4-40 x .750" screws are used here.
the screw should penetrate the nut as seen here.
lynxmotion.com/images/assemb … dof309.jpg
using a small pair of pliers, hold the locking nut, then using an allan key or “hex key” turn the screw though the nut. remember to use the washers provided.
Hi thank you for your reply.
Yes I see the picture. Does it mean that the screw have to penetrate the nylon and go all the way through ? Meaning in someway destroying the nylon ?
yes, but it shouldn’t destroy the nut its self. it will bur out the inner surface of the nut. is that what you mean?
nylon locking nuts are meant to be non-return. meaning they should in effect not untighten. never reuse locking nuts.
Alright, I suppose that we need to have a considerably large force to turn the thing in.
Another thing, do attach the ball bearing we need to use a lock washer, i find it difficult to the screw in if were to use that lock washer,
is that OK to use just a normal washer for that ?
Attach the Ball bearing, using a 2-56 x .250" screws and 2-56 nuts. “the standard nut”. not need for a lock nut here. just be sure to use the 3mm locking washer. 
The forces required to properly tighten a locking nut or compression washer are not that great! I believe you may be building with the wrong tools. To properly tighten down a locking nut you need to use a properly fitting #2 Phillips screw driver or 3/32" hex tool depending on the screw type, and on the other end a set of pliers, or better a 1/4" socket driver like this.
http://www.robotshop.ca/Images/big/en/elenco-nd-3-nut-driver-set.jpg
In addition, if you can not tighten the screws in the bracket mechanical assembly very tightly you may have problems with things coming loose. If you do not have much arm strength, I strongly recommend you use a thread locking compound such as locktite on the screws that do not have lock washers or nylon locking elements.
What if I do not use the locking washer ? The reason to this is because the lock washer makes the bolt seem shorter and its quite difficult to screw the nut at the other end.
Will a normal washer with flat surface do the job as well ?
If you do not use the 3mm lock washer then the ball bearing will be unable to turn. You’ve gotta press rather firmly, but it can be done. If you’re having trouble with it, try taking a pair of pliers and flattening it a bit.
Is the locking washer being used to to restrict the movement of the motor to a certain degree ?
Because it is funny that whats happening is quite different what you have said, I have 1 leg that had a normal flat surface washer being attached while another leg has the locking washer attached.
The one with locking washer attached actually has restricted angle of movement when I played with turning the motor.
Post clear in focus closeup images of your assembly. No amount of writing will adequately describe what you have built. There is nothing in the bearing assembly, washers or not, that would restrict the motion of the axis.
Where did you get such on old kit?
Really appreciate for the speedy reply just now.
But i think i have found the problem, somehow I place the motor the other way round. Its moving good now. 
