Originally Posted by brucehatch
I'm just starting on my empenage kit and opted to purchase the Numatx system over the standard pneumatic squeeze. Tool performance was very anemic following my first attempt at infusing and bleeding the Dexron III fluid into the simple hydraulic circuit. A second repeated infusion did the trick.
I get acceptable shop heads at 72 psi for -4 (1/8") rivets and 43 psi for -3 (3/32") rivets. I'm sure the readings on my pneumatic gauge will very a bit from any other.
Is there an optimum pressure to use for dimpling? My operating manual is blank on this. Should maximum pressure be used for all dimpling regardless of stock thickness?
Never got a response to my questions regarding recommended pneumatic pressure during dimpling so I inquired with the Numatx tool developer via a PM. Here is his reply:
I guess the short answer is run the pressure up to as high as you would for riveting. This assumes you are dimpling with the squeezer and a yoke mounted in it (I think this is what you are meaning), as opposed to the squeezer mounted on the end of a C-frame (DRDT-2), which could caused too much stress in the c-frame.
The simple fact is you can not over squeeze the sheet stock, the hydraulic pressure would have to be astronomical to do so. If you doubt this, but a set of flat dies in the squeezer, and squeeze a pc of sheet stock. It wont do anything to the sheet after you release the pressure.
I personally think people get to fussy about the dimple quality, but to each their own. I taught sheet metal to A&P students, and didn't fuss over dimpling to the degree some do. Don't take my comments as a knock on you asking the question, I don't mean it that way.
I hope this helps.