ORIGINAL: carrellh
I've never heard of a 'non precision' hole. APC and Master Airscrew have a stepped hole. The center hole is usually 1/4 and the bigger hole is usually 5/16 since these are very common shaft sizes for many popular glow engines.
I see... I was afraid that the 5/16 hole may not be centered as precisely as the 1/4 inch hole. So I assume they both are centered pretty well.
I experienced what seemed to be severe vibration, on my SIG Kadet Senior, while the engine was running at low RPMs (2500). So I decided to get a prop balancer. The engine (OS .46 LA) is brand new, and has been broken in. I believe that I managed to fine tune it as well. It has a Max RPM of 11,500 and an idle at 2500 - 2750.
I checked over everything such as mount to firewall and engine to mount... they are all snug as a bug.
Unless the vibration I mentioned is normal, than I assumed the prop is out of balance.
The Senior has a large Air Frame, and the covering is wicked resonant. Mabey the vibrations I was seeing was normal?
I intened on having a gentleman at the local club check it out anyhow, but I thought I'd post to get some opinions.