I am sure that you have the right tubing and fitting(s) BUT tubing can be tricky. A lot depends upon the thickness of the material. Try this. Put the fitting in the freezer for about ten minutes and swirl the end of the hose in some very hot water to soften it a bit. If you cannot get the hose to slide over the fitting, I'm sorry; it is beyond my ken. One more thing, put a hose clamp on the fitting because no matter how tough it is to put it together, if left to itself it will come apart. It obeys one of Murphy's laws.

A trick that makes it MUCH easier is to spray the end of the poly tube with WD-40 or the like. It's still a pain to slip the tubing into the sleeve, but this will work wonders. Good Luck.

Don't use WD-40, the solvents in it can hurt the tubing. The better lubricant is KY-Jelly because it's water based.

I just had to have my well pump replaced. It uses 1" PE tubing. The serviceman just hit the tubing with a quick blast from a propane torch and slipped it right on. (and no clamps) He said he'd done hundreds like this without a problem

Oh wow, I didn't read this post until after I posted mine. I am going to try lighting the end of my 1/4" tubing with a cigarette lighter and see if that works. I hope I won't breath in toxic fumes though! Is k-y jelly petrolium based? If so, I'll just stick with the vasaline I've been trying. It's good to know I'm not the only one with this problem! I agree with the poster...these need a severe engineering upgrade! I'd pay twice what I'm paying to avoid this pain in the ...behind.

Try using a heat gun to heat the tubing just a little. This will soften it just enough so that you can insert the dripper securely. When the tubing cools, it forms a tight grip. It works very well and your problem should be solved.
A hair blow dryer set to hot should also do the trick.

Good Luck

You have a lot of advice here. One thing I've noticed is that different manufacturers of tubing have different overall width. DIG is .700, TORO is .710, Fiskar is .480. Be sure the tubing and the fittings are from the same source. I use a coffee cup with hot water to soak the connecting end..........haven't had a problem

Marystem-what a great header topic!

Has anyone found It easier to install connectors into a header hose that is larger than 3/4"? We have the correct tool/punch (certainly makes a clean hole), for the connectors, but the effort to connect is nearly impossible. Will try all of the above suggestions.

Has anyone found a tool that would push the connector into the header when one is 'in the field' and does not have access to hot water, torch, clamps, etc?

If you have the right fittings that will work with this item, then working with it in the field is your answer. You can use the pocket punch or the punch n cut. Your fingers will thank you!
http://www.youtube.com/watch?v=ieUrCaJ9XGU
http://www.youtube.com/watch?v=P8qYHUNzrc4

stevec and Ibanez, Your suggestion works!!! Could not believe that 1-2 sec is perfect! Thanks so much!

You are saints in our estimation for sharing a simple solution. No more sore joints.