Pneumatic Squeezer Squeezes, Won't Unsqueeze

I bought a CP-214 pneumatic squeezer on eBay for my RV-9 build. It came with a fixed set holder, so I bought an adjustable set holder from Aircraft Spruce. I figured out how to install it, lubricated it... had a heck of a time getting it to seat properly... but did finally get it on there and get the yoke back on.

Hook it up to the compressor and it squeezes, but the set holder won't return to its original position. If I push down on the set holder with firm thumb pressure (with fingers well away from the trigger!), I can pop it back down, but when I press the trigger again, same problem. The spring that came with the set holder is in place, but it seems like it lacks the oomph to overcome that resistance. The squeezer does cycle properly with the set holder that came with it.

The square base of the adjustable set holder is a tight fit, and it doesn't come out easily when I pull on it. It's possible it's hanging up on something inside, but I can't see what. Dr. Google hasn't been much help. Maybe I got a dud, but which part is the dud, the set holder or the squeezer? Should I try grinding down the sides of the square base to get it to move more easily in the channel? I thought I would ask the experts here. Thanks!

Interesting you say that. I bought one on ebay that was advertised as new and it did the same thing. It had no returns so I protested on ebay to get my money back.

1) Remove the yoke and return spring to see if the set will return after the trigger is released with finger pressure equal to the spring return pressure.

2) Verify the air pressure has a release path after the trigger is released. This is usually a small hole at the bottom of the squeezer body, below the trigger. Air must be able to escape the chamber after the trigger is released.

3) Check the circumference of the set compared to the circumference of the hole in the yoke. I have two yokes that I had to ream out in order to allow the set to run smoothly in the set/release directions.

4) Remove the set from the squeezer body and verify that the piston runs freely up and down.

Make sure that the adjustable set is able to move in the yoke when the yoke and ram set is out of the squeezer. When I built my RV-10, the adjustable ram for my squeezer came from Avery and was very high quality. I sold all my tools and had to buy new again for my 9A. The adjustable ram set I got this time from Spruce did not slide freely in the yoke and I had to polish it in a few areas to get it to slide without binding. Working it up and down, I could see where it had interference when I pulled it out and hit that area on the de-burring wheel. I figured I got a bad one and just fixed it that way instead of returning it for a replacement.

The only purpose for the "square" head on the adjustable ram is to provide a bias that allows the ram to be adjusted (in or out) without the threaded base rotating.

When the square head is in the cast squeezer housing (also square), they "pair" up to resist rotating when the mandrel is adjusted in or out. It really doesn't matter how loose the fit is, as long as it will prevent rotation when the mandrel is being adjusted.

The adjustable rams I make are all a very loose fit inside the housing to help insure there are no "hang ups" during cycling. I just grind the sides until I get the clearance I want.

YMMV

HFS

Ram

HFS said:

The only purpose for the "square" head on the adjustable ram is to provide a bias that allows the ram to be adjusted (in or out) without the threaded base rotating.

When the square head is in the cast squeezer housing (also square), they "pair" up to resist rotating when the mandrel is adjusted in or out. It really doesn't matter how loose the fit is, as long as it will prevent rotation when the mandrel is being adjusted.

The adjustable rams I make are all a very loose fit inside the housing to help insure there are no "hang ups" during cycling. I just grind the sides until I get the clearance I want.

YMMV

HFS

Click to expand...

Agreed. Mine is pretty sloppy inside. If that's where it binds, just grind the two sides equally so it stays centered(ish).

My adjustable plunger has flat and rounded ends (old Avery) It fits in my Avery hand squeezer and pneumatic opposite, rounded end to the open yoke on one and to inside on the other. If inserted wrong it will bind. Try rotating it 180 degrees.

Thanks very much to everyone who responded! Some observations from the workbench just now:

• The set holder slides freely in the yoke when both are off the squeezer.
• The spring does push the set holder back down in response to thumb pressure from below (as if from the squeezer).
• There is a release of air from the bottom when the squeezer trigger is actuated. The fixed set holder that came with the squeezer returns to the down position when the trigger is released. That set holder has a circular base, so it doesn't mate to the sides of the channel.
• The adjustable set holder base only fits one way; there's a side that has a reduced size that fits between the steel plates that attach to the yoke.
• This is an Aircraft Spruce set holder, and it sounds like it's not unheard of for these to need a bit of grinding. Mine does fit rather tightly in the channel (to the point where you really have to cram it down past a point), so I'm inclined to try grinding down the sides of the square base by a few mils on the sides to loosen it up a bit. I'll have a try once I've tidied up my workbench (which accumulated quite a mess while I was priming) so I can get to my bench grinder, and I'll post my results for posterity.

As Gyoung suggested, try spinning the adjustable set 180 degrees in the squeezer base before you install a yoke.

I?ve had my set for 20+ years and the correct orientation still *appears* 180 degrees out of whack to what it should be in my mind?s eye. Mine binds in the up position when I install it 180 degrees out of kilter.

Success!

Thanks again for your help everyone! I ground down about .010" from the width of the adjustable set holder base on a Scotchbrite wheel, and it now squeezes and unsqueezes with the best of them. Excited to finally start riveting!