It's not often that we post directly into different user groups. However, one of our customers suggested we look at the thread on pneumatic squeezers, yokes, etc. What we're posting is factual in nature, so we're going to try to omit any personal opinions, vague generalizations, misinformation, disinformation, and baseless "jokes" comments.
The current version(s) of the CP-214 pneumatic squeezer have been produced for over 50 years by a number of different companies. Now they're also being produced offshore. There are numerous "variations" to the different models, even by the same manufacturer. However, one thing ALL models have in common (or maybe SHOULD have in common) is the yoke bolt pattern. Therefore, yokes manufactured by any company should fit ALL the squeezers on the market.
As yokes increase in Reach, they generally require more material for stiffness, i.e., so they don't flex. Therefore, you will typically see "taller" bases requiring longer set holders once you move into the 4" reach and above for portable yokes, i.e., not bench mounted. Depending on the design, the taller base may interfere with the standard bearing cover plate on top of the squeezer. The solution is a shorter bearing cover plate. A shorter bearing cover plate can also be used with any of the standard yokes.
Yokes are designed to bolt into the steel sideplates of the pneumatic squeezer. Bolting the yokes in provides additional rigidity, ensures correct alignment with the set holder and cam, AND MOST IMPORTANTLY, prevents the yoke from rotating when applying pressure to the rivet.
Think about it. Every time you squeeze a rivet, you're applying 3,000 lbs. of pressure to the yoke. Quick change pins don't provide a high tolerance fit. They are also made out of softer material than the Grade 8 bolts generally used. As pressure is applied to the top of the yoke, the yoke will rotate around those quick change pins ever so slightly. As time goes on, you will generally find that the quick change pins become warped, difficult to get out, and you can see distortion on the shop head of the rivet. That distortion can either be from a yoke flexing or rotating before flexing.
Adjustable set holders are not standard equipment from any manufacturer for pneumatic squeezers. However, different variation have been in use for years, each made by a manufacturer to fit their particular squeezer.
The biggest problem with the two most popular adjustable set holders currently on the market is that the shaft is female threaded. Their walls are approximately 1/32" thick and they are prone to compression problems. Using the proper materials and heat treating those materials properly can also be a problem. Suffice it to say that if the heat treat is too high the material becomes harder, but more brittle and prone to snapping under compression loads. If you don't have enough threads holding (shaft is over-extended), you can also strip out the threads at the end of the shaft travel. That is why some adjustable set holders are advertised only for use with yokes that have a 1" base.
We originally put over 50 hours of engineering time into designing our adjustable set holder. It worked on every single pneumatic squeezer that we could find and test it on. Then we found out that Chicago Pneumatic had, at some point in time, changed their castings. After putting in another 60+ hours of engineering and testing, including sawing pneumatic squeezers in half, we ended up making some significant design changes to accomodate casting differences of .020" or less. Bear in mind, that out of all the adjustable set holders we've sold, including those to various aerospace manufacturing companies, we've only had 3 of them returned. This variance we discovered may only affect 10% of the squeezers on the market, but we felt it had to be addressed, and we did so. In the long-term we may discover other variances or problems and address them accordingly. Nothing's perfect in life, but you'd be surprised how hard most people work to do the right thing.
Ok, we can't resist -
One of the nice things about building an experimental aircraft is that each individual can do it "their way". However, having factual knowledge of a process can only serve to help individuals make better informed decisions. Demeaning and flaming serves no constructive purpose - it's just character assination. As a tool company, we have a responsibility to provide the best service we can to our customers. Individuals would seem to have the responsibility to educate themselves so they can make the best decision they can on what's right for them. Doing otherwise, by either party, and people have a legitimate right to question what the agenda is.
Thank you for your patience in reading this long post. Hopefully it will help someone now, or in the future.
Fred W. Kunkel
CLEAR AIR
www.clearairtools.com
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