Prop drilling techniques???

[fabmaster911]

Hi, do any of you have any insight if there is a right or wrong way to drill a prop? I already made one mistake and used the wrong holes on my drill jig. I also used the right ones. Is this prop junk now because of structural integrity? Any tips will be appreciated. Thanks

[stommerd27]

I probably wouldn't use it. It might be ok but why chance it for safety reasons. The main thing I know about drilling props is you want to drill from the back side through to the front. And then just like any thing else you drill let the drill do the work don't force the bit through let it go through on its own. And oh yeah use a drill press so that you know you drill it straight.

[RustyTumbles]

Also drop the bolts through the jig and the prop as you go. This will help stop the jig moving while you are drilling.

[Rickster]

Lay a piece of hardwood on the table of your press so that when the bit passes through the prop it will not rip the exit hole up. Also on the prop with both patterns now, you can take some dowl pin the same diameter as the extra set of holes you drilled and cut them to length and glue them in with wood glue and use the prop as usual, never had a problem with them..

Rick

[Oilsands]

I would check with the manufactor about using the prop, they should know whether you can use it safely or not (that is if you are looking at using it).

[bgold]

I have a piece of wood on the back so the prop won't break out and I clamp the jig, prop, & wood to the table. as I drill each hole I put a drill the same size I'm using through the jig and hole upside down. The shank of the drill will be the size of the hole you just drilled, most of the time the bolts are smaller than the hole and some movement could happen. When I finish drilling the prop I remove the jig and then re-drill the holes with a drill about about 3 or 4 number sizes larger, usually about .012" -.015". I then hit each side with a countersink to make about a 1/32 champer to finish the holes.

[DR10044]

1. Use a jig.
2. Use a drill press.
3. Pin the holes as you go to keep the prop from slipping.
4. Drill from the back. Check to make sure prop will be at 2 o'clock position.
5. Put a piece of scrap wood under the prop to keep it neat.
6. Drill slowly, less chance of the prop slipping or trying to run on you as you drill.
7. I balance the prop after drilling.

[Simpleton]

I once came upon a discussion about drilling props that said to put 2 opposing holes at 3 and 9 O'Clock, in line with the center hole. The thinking was that there were no continuous structural elements in this region since they had already been severed by the center hole. This way, there are some uninterrupted lengths of prop at the hub just above and below the center hole. If you put opposing holes at 6 and 12 O'Clock, then those holes along with the adjacent 2 holes and the center hole interrupt the continuity of the prop material throughout the entire hub region. Whether or not this theory has any merit, I can't say, just food for thought and discussion.

[Al Lewis]

I always use the directions on the manufacturer web site. www.vessaero.com

[phippsj]

Sometimes you have to clock the holes at a certain orientation to clear the mounting tabs on a spinner base plate. These are more common on the carbon fiber spinners. Spinners with center bolts are not a problem.

[The Dirt Doctor]

	Quote: Originally Posted by Al Lewis
	I always use the directions on the manufacturer web site. www.vessaero.com

This is perfect for the outer holes (i.e. DA 3W 150). The inner holes (DA 100 3W 106) should be rotated such that the top two holes are parallel to the centerline of the prop (as in the outer holes shown in the photo).

After drilling the holes as above be careful to install the prop such that as the prop rotates the pistons come up on compression when at the 2 o'clock position.

Works perfect every time.

Bobby aka TDD

[forgues research]

The drill jig I fabricate for the Evo engines have a small 10 mm peace sticking out that fits into the prop, from the other side, I bolt a 1/4*20 screw tightly so the jig doesn't move, then you can drill safely with a hand drill ...

Always, always rebalance the prop after drilling or doing anything to the prop.

Roger

[Spocky]

	Quote: Originally Posted by forgues research
	The drill jig I fabricate for the Evo engines have a small 10 mm peace sticking out that fits into the prop, from the other side, I bolt a 1/4*20 screw tightly so the jig doesn't move, then you can drill safely with a hand drill ... Always, always rebalance the prop after drilling or doing anything to the prop. Roger

I use a very similar method to this and it works very well, only tip that I could add would be to use high rpm's and a slow feedrate with the drill. I have only had experience with carbon props though.
On another note, could anyone supply link or info on the best balancing method for large 30" + props. Especially 3 bladers.

Thanks

[alec taylor]

a few spots of ca onto the jig befor drilling and it wont move.

[Tired Old Man]

3w has some good instructions about drilling props in their engine manuals. You can download a manual for free so you might want to take a look. www.aircraftinternational.com

Drill the holes wherever as long as they permit the prop "referencing" you desire. Most like their props to be at a 1:00 or 2:00 o'clock blade position when the engine is against compression. Some may not so adjust to suit.

Drill props from the back to the front. Then flip the prop over and redrill the same holes again. Over drill the holes after the first pass through the jig to the next number size larger than the prop bolts.

If you drill a hole in the wrong location, stop right there and do not try to "off center" a hole connected to the original mistake. Obtain a wood dowel that will tightly fit the hole drilled in error or enlarge the hole to a size that will permit a wood dowel to be tightly fit into it. Epoxy or ca the dowel into the mis-drilled hole, cutting the dowel flush on both sides of the prop. After that is complete, drill a hole in the correct location.

The prop will be fine. Balance the prop and go fly.