The APC were designed to be used with an adaptor insert on the back side. The thin web in the middle of the hub is thin, so it is easy to ream, but would provide a stop for the insert. I used to get metal inserts directly from Fred Burgdorf years ago at the pylon races we both competed in.
This was after he raced for many years using Rev-up props, since it was several years before APC were allowed in the event. When Rev-up props became difficult to get, the APC props were finally allowed in competition. The production at Rev-up pretty much came to an end when Chris Machin's wife Ethel died. I had worked for him part time during college, which at that time his rival was Mike Schlesinger of Top Flite models. Chris didn't think too much of other props made back then, but he talked a lot with Mr. Schlesinger usually about costs and pricing.
About wood props, there were two things that Chris was adamant about with wood props.
First, always flex the blades so the wood grain could be proven strong enough to put on an engine. This applies to new props or one that have made slight contact with the ground, and especially any that have been modified.
Second, always ream the hub enough that it will freely slide onto the shaft. Too tight, forced on, or especially on some engines where there is a slight change in shaft size next to the drive washer. Any of those conditions can split the grain right at the hub when you tighten down the prop. Thrown blades are exciting, but an unbalanced prop from losing a blade can destroy an airplane very quickly.
Oh, the masking tape works pretty good in a pinch for centering. Better than most reamers.
Topic: Bushing for LA15 props (Read 2510 times)