Just about to finish up an airplane, first one this big. Question: Does anyone make a reamer big enough for a BME 100, or do I have to drill the prop? If drill, what size bit?

tia

I am going through the same problems with my BME 50. I have not found a reamer large enough (7/16") that will do it. This website http://www.bennettbuilt.com/ has a stepped drill bit in the correct size for around 15 bucks. It has a 1/4" step in it so it guides itself through the stock hole of the prop. Make sure you use a drill press!

Good Luck.

Guys, do yourself a favor. Go to Home Depot or similar and find a UniBit (#1 Size). This is the best thing since sliced bread for drilling props. It steps up at 1/64" and is pretty much self-aligning. Drill until you get the EXACT correct size starter hole, then switch to a regular bit of the correct size.

Craig.

Now wouldn't it be great if BME used a 10mm crank stud so you wouldn't have to drill the center of the prop? If you haven't already noticed, the majority of "good" props for the big gassers come with a 10mm hole.

.... or even a standard size drill bit. I couldnt tell for sure if it was SAE or metric.... 7/16th ? wassup with that?

The fact that you have to drill or ream the prop to fit a BME is the reason I will never own another.

Todd

A). . the BME series of engiens takes a 7/16 drill bit to match the prop alignment portion of the crank

B) Saying you will never own a BME due to this design feature is silly. I guess you would rather drill six imperfectly aligned (no matter what jig you use) 5mm (or so, since 5mm drill bits are VERY scarce) for your DA's.

C). . if you still want to maintain the original 10mm prop center hole, its very easy to use a partial depth hole in the propellor, which is just siffucient to slide the prop over the entire alignment part of the output shaft, and leave the rest of the prop hole at 10mm diameter. I have several props drilled with both the undercut for the BME, and the small 6-bolt pattern for the 3W 100 so that I could use the same prop on both engines. . no problems or issues. And if you are worried about centering a spinner, spacers are available from every spinner manufacturer to match whatever engine you are using .. and the outer diameter of the holes is 11mm/ 7/16" !!! BEFORE the spacers are inserted!


Hope this helps!

Six imperfectly drilled hole no matter what jig you use ??
A good drill jig, made on a milling machine, will have the holes perfectly drilled within .002 of true position..When the prop is drilled with a #9 drill there is no way the holes can be mis aligned...Both 3W and DA sell drill jigs made that way..I know, I made the first ones for both companies...They had 12 holes, so they could be use for either pattern..
Large 3W and DA, 1.330....
Small 3W and DA, 1.133....

Must be that my 10-speed Craftsman drill press is out of spec, then. . even if I CA the adapter to the prop so it can't possibly move, then pop it off after drilling, there is always ONE hole that is off a little. I always wind up chasing the holes to a larger diameter to get rid of the binding.

Drilling 6 holes? Drill from the backside (mounting face of the prop), after you drill the first hole, drop a spare drill bit into the jig and prop to maintain alignment, drill the other 5 holes. It's perfect. The 6 holes don't have anything to do with prop balance anyway - it's the 10mm hole that centers on the stud. The 6 bolts just provide even clamping pressure.

IMHO, the best solution is to get a 7/16" reamer. These are available from any machine supply store for under $20. I have a 10mm reamer like this that works wonderfully. Drill a 3/8" hole, ream to 10mm and it's perfect. The props that come with the 10mm hole in the center don't seem to have the tolerance that I can get with the reamer. The Bambula's are the worst with (I'm guessing here......haven't measured) around .007 too big of a hole.


-Aaron