prop reaming problems

Sounds like you need an x y vise. Put the prop in the vise and the same size bit in the press. Without the press running, put the bit through the hole in the prop. Now change out bits and drill the correct size hole.

Maybe someone else has a way to save the one you misdrilled, I don't.

Toss it in the trash. I don't think there's any hope for it.

Get the appropriate hand reamers. You can get up to 8 or 9mm with the standard reamer, and there are larger prop reamers available.

You could also get a "Unibit," which is a step drill. Even if the Unibit isn't long enough to drill all the way through, you can still get a starter hole for a regular 10mm drill bit.

Hmm, I suppose you probably held the prop when you drilled it instead of clamping it down. You don't need anything as fancy as an X-Y vise, a regular drill press vise would be just fine. Similar to what JR said, put the prop in the vise, use a drill bit that fits in the original hole to center it, and clamp down the vise, TIGHTLY.

I've got a Saito 180 with a 10mm shaft and have had no problems using the Fox hand reamer. See the link below for Tower Hobbies - I got mine at my local hobby shop.

I agree with Mathew. Although I have the press and vise, I use hand reamers to do the job. It's quicker. If you get a hand reamer, I would suggest the Fox ones. The Great Planes ones do not cut as well, unless they have changed them recently. Depending on the engines you own, you may need two, an SAE one and a metric one. I also have a tapered ream that I use on some props when the hole is close already. Remember, it's getting it centered on the shaft you want. If the middle is thin, that's fine as long as there is enough meat around it to tighten the nut/washer down on.

Another tip from a pylon racer in our club works for me. Use cheap fingernail polish to balance the prop instead of trying to remove material. If you put too much on, you can remove it with acetone and try again. If you pick the right color, you can almost see the prop tips when the engine is running. I hate throwing new props away.

JR

PS. The x y vise is handy for a lot of jobs and Harbor Freight sells some pretty cheap.

It is extremely difficult to enlarge a hole accurately by using a drill press. The above methods, clamping the prop in a drill press vise and BOLTING it to the table is a good method that still can lead to problems. (If the table isn't square to the spindle of the drill press, the hole can be drilled at an angle. Some cheap drill presses are off a mile here) If you know someone who works for a local machine shop, have make a piloted drill bit. Take a drill (I think it's a Z size) chuck it in a grinder and grind the down the first 1/2 inch to match the I.D. of the existing hole in the prop. The very best method is, as previously mentioned, using a hand reamer and taking it in steps until you get to the appropriate size. Someone used to sell a prop balancing setup that drilled the hole offset and used bushings, Don't remember who. (Senior moment) You might be able so salvage the prop. but I'd probably just trash it. Good Luck Bill

I haven't found anything that works well without making the balance worse. I use a prop holding fixture I made, and indicate the original 1/4" hole within .001. I then use a 2 flute end mill to bore the hole to size. I have also used step drills, and drilled the hole to size using smaller drills and stepping up to size, with the same results. The fixture I use is an aluminum block about 4"H x 4"L x 2"W. It has a hole drilled in it for clearance of the cutting tool, and 1 taped hole to tighten the holding clamp. The holding clamp is yoke shaped so it can hold on each side of the hub in the center and allow for indicating the original hole. There is an adjuster bolt for height to allow for the difference in thickness of the hub. I clamp this in the vise of the Bridgeport mill and skin cut the top surface to make sure it is perpendicular to the spindle. I just did 3 APC 13 X 8 props this way, and all 3 got worse. If you are familiar with APC props there is the original 1/4" hole in the front, and a larger c'bore hole on the back side. This hole on the back side is about .320 in diameter. The size I bore my props to is .312, so you can see if there is any misalignment between the hole you just made and the original. The interesting thing is that all 3 holes were off location to the original .320 c'bore hole in exactly the same direction, and the same amount. The holes were offset slightly to the side of the prop that gives its size in metric. Also just slightly to the side that has C-2 molded into the hub. This would make the blade that had the size in English numbers heavy, and the prop hub will fall with APC logo down after getting the blades to balance. This leads me to believe that the 1/4" hole is slightly off in relation to the larger hole in the back, and the larger hole is the one that is actually the one that would give the proper balance. Using the .320 hole to indicate the prop is more difficult to do because the front face of the prop hub isn't really a good surface to locate the prop on. I was thinking of making another fixture that would allow me to locate on the back surface of the prop and indicate the .320 c'bore, and then open the hole to size. Drilling or reaming a hole in the prop is the easy part. Getting it to balance is the time consuming part, that I would like to eliminate.

Greg

"gord" wrote in message news: snipped-for-privacy@sprint.ca...

How to do it better next time :

Before you trash another prop, go visit the metal working news group and find out how to tune up that drill press.

A good book is "Drill Presses - How to choose, use, and maintain them" by Rick Peters. Barnes and Noble has it. Cheers, Fred McClellan the dash plumber at mindspring dot com

A good filled epoxy should permit this to work. Then again, if you had the skill to do this sort of recentering operation, you wouldn't have gotten into this pickle in the first place. I am using "you" figuratively.

Ed Cregger

Some company in the past sold a balancing gizmo. You bolted the prop in the balancer and slide the prop around until it balanced.

Once the prop was at the proper balance position you would drill thru the gizmo's guide hole to re-centering the prop shaft hole to balance the prop.

I don't know if there are still sold, be it sounded like a neat idea.

Try a high temp epoxy such as JB Weld. The stuff has been used to fix auto engine blocks, so it would probably stand the heat.