BlackB12

My Feedback: (9)

Ordered a new prop for my ST3000 (18x8) and it came with a hole about half the size of the ST's shaft. From measuring the diameter it appears I need a hole that is 10mm wide. Can I simply get a metric drill bit and drill the hole bigger or is there a risk of not getting the enlarged hole perfectly centered? Should I find a stepped reamer to enlarge it and keep the hole center?

Also, does anyone know where I can find a non-rediculously priced 3.5-4 inch diameter spinner for this plane? I found that Top flight's P-40 spinner is about the right size but the cutouts are nowhere near the right size. I'd have to remove a lot of material to make it fit, and then I'd probably lose the balance. I know aluminum ones will work, but I'd like a white one for this plane.

http://pic6.picturetrail.com/VOL171...21/66573849.jpg

MIke

glowplug

My Feedback: (1)

I use a stepped reamer to enlarge my prop holes........I'm no Bob Vila with a drill, so I'm afraid to drill the hole slightly off. I guess if you had a drill press, that would work good.

Look into Tiger Shark spinners........I think that they are distributed by Kangke......I think they're relatively reasonable.

bigchap

i use a bodyshell drill for rc cars to ream props,it has a nice slow taper so is much more accurate.

MinnFlyer

My Feedback: (4)

If you have a drill press (Or have access to one) using a drill is fine. The drill will find its way to center and follow the existing hole so long as the prop is free to move side to side.

ballgunner

My Feedback: (1)

I use both a reamer and a drill press. The trick to both is to be sure you drill 90 deg. to the axis of the prop. Drill press tables are almost always adjustable and at times get out of square with the drill. Check very carefully that the bit is actually verticle to the table. I usually use one number size smaller drill than the prop shaft and finish with a reamer. put a flat piece of wood under the prop while drilling. Don't depend on the hole in the center of the table to clear the bit or you will splinter the backside of the prop.

mulligan

Sorry, Minn, I have to contest this. I've heard this before and I don't agree. If a drill bit could "find its way to the center," there would be no reason for a reamer. Drills dig and reamers shave. The digging of a drill bit causes it to wander, even after the hole is started- the deeper the drill bit goes, the more stable it is, but the natural wandering forces are always there.

Having said that, smaller props probably won't notice the difference, but the larger the prop (and hole), the more critical the center position. In any case, if the hole wanders too much, you might not be able to balance it at all; and even if you weight balance a prop with an off-center hole, there will be an aerodynamic imbalance, which will cause an asymmetric prop blade arc and a resultant odd sound.

Ed Smith

I agree with G.M. Drilling out a prop on the average "Home" drill press is a very hit and miss affair. It will not end up in the middle. Even with a tapered reamer, apart from the very front of the hole the rest is way oversize.

In addition, depending on the prop material, the drill bit may bite and pull the prop up off the table and totaly ruin the hole. Try this. Find a drill bit that is the same size as the existing hole. Put it in the drill chuck and push it through the prop hole to position the prop on the table. CLAMP the prop in position on the table with a wood base underneath it. Now drill out the hole using two or three drills until the final size is reached.

If you realy want to spend some money get a three fluted drill bit.

ED S

JoeAirPort

My Feedback: (41)

I use the GP step reamer (7/8/10mm). Then I bought a precision 12 mm reamer for about $17. I use a drill press and let the prop float on the table, but sit flat. I just hold it with my hand. The prop never grabs and turns violently because I'm taking off so little in each step. So it's very safe. It makes perrrrrrrfect holes every time.

By the way, I have a Moki 1.80 that I've done 3 props for lately and the hole is 10mm. Then I do a 12 mm ream 5mm deep form the back of the prop. That's because Moki's shaft is 10mm on the threaded part and 12mm at the base.

Joe

50+AirYears

Ever since I bought the Fox english and metric step reamers, I've had less problem with prop tips being out of track because of the drills wandering during use.

khodges

My Feedback: (1)

I, too agree with The others who say DON"T drill. True, the small props probably won't matter, but you've got to be dead nuts on center for that size prop. Even with a press it will be difficult to drill it and not "wallow" the hole a bit; even hardwoods have "soft" areas and a drill will cut them faster and more ragged than the hard areas (I'm talking in millimeters). A drill bit cuts from the angled surfaces at the tip and will hunt for the softer path, a reamer cuts from the side, and the tip is only guiding it. Step reaming is the best way to go. If you had NO hole, but could mark the exact center, you could drill with a brad point or Forstner bit at a low speed in a drill press, but that isn't an option with a pre drilled hole.

CAPtain232

My Feedback: (40)

The technique that ED SMITH described is exactly what I do. I have every drill bit you can think of up to 1/2" (WIRE NUMBERS, LETTERS, METRIC AND STANDARD). I find the tightest fitting drill bit, chuck it up in the press, insert it in the prop hole and the lower it to the table and clamp it in place. Obviously I then drill it with the appropriate drill bit. I do not even bother stepping up to the correct size with smaller bits, I just feed the correct bit at a nice slow even pace.

I can tell you that this method is very accurate as I like to BALANCE my prop before I drill the hole. After I drill the hole, I recheck the balance. 99% of the time the balance is still perfect. This tells me that I got the hole dead center of the original hole.

Try it out if you have a press. Works very well.

MinnFlyer

My Feedback: (4)

Continued

Pic 5: The prop sitting snugly on the drill (I couldn't hold the prop on a 1/4" with the original hole because the hole was too big)

And a close up of the hole to show you that it's not gouged (The marks you see are grains in the wood and would look the same had you used a reamer)

So why do they make reamers? Because this hole may have been oversize by a thousandth of an inch or so (Still better than factory specs) and SOME applications require VERY precise sizes. But using a reamer on a prop is like sweeping the Kitchen floor with a tooth brush. It will do a very good job, but it's just not needed.

Your Honor, the defense rests.

(I'd have made a damn good litigator!)

MinnFlyer

My Feedback: (4)

Oh ye of little faith. Don't believe me? That's ok (God knows I can be opinionated ) But will you believe your own eyes?

Look at these pics (I want you all to know I ruined a perfectly good prop to prove this point)

Here is a prop that I just bought 2 weeks ago, so for all intents and purposes, it's brand new.

Pic 1: The original "1/4 inch" hole, which as you can see measures .255" (Which for you who don't play the decimal game is .005 [5 thousanths of an inch] LARGER than 1/4" ) To put this in perspective, a human hair is .002

Pic 2: a 9/32 (.28125) drill bit

Pic 3: With the drill NOT turning, tap the drill against the hole a few times as you allow the drill bit to move the prop in place. When the drill stops bending, it's lined up. Turn on the drill, and drill the hole.

Pic 4: Compare the measurement to the drill size. The hole is the same size as the drill. Not only that, but it 5 thousandths of an inch BETTER that the hole from the factory!!!!!!!!!!!!!!!!

(To be continued)

mulligan

as if...



uh, Minn, wasn't the point not that the hole would be the size of the bit but rather that the hole, as enlarged, won't be concentric with the original hole?


Incidentally, counselor, I didn't see the cal. sticker on that caliper. If the drill don't fit, you must acquit!

MinnFlyer

My Feedback: (4)

LOL!

You know, I though of that late last night too. I should have measured from center to outside before and after drilling.

Maybe I'll do that. I'm having company for dinner tonight, but if they leave early, I'll play with it some more.

PS, I know you won't believe it till the pictures are in, but it WILL be concentric.

mulligan

Take your time. I'll soon be sipping umbrella capped drinks in the Carribean- see you in a week or so!

But if I may suggest, using calipers will be difficult. The hub of the prop isn't round, so you can only measure in one spot circumferentially. Instead, if you have a scanner bed, enlarge the hole 1/8" on dia. and do a before and after scan; then overlay the images and see what you get.

BillyGoat

I read somewhere about using a drill press to “ream� a prop hole. Secure a piece of wood to the drill press base and drill a hole into it using a bit the same size as the hole in the prop. Insert a wood dowel into the hole you drilled then put the prop over the dowel. Now you can drill the larger hole without the prop wondering and the bit will track better cutting through 100% material.

Never tried this but I really like principle. The only difficulty I see with this tip is finding a wood dowel the right size. However I suppose you could chuck a larger dowel in the drill and sand it down to the right size.

MinnFlyer

My Feedback: (4)

Actually, this is not true. One instance where a drill will NOT track properly is when it is cutting 100% material. This is due to the fact that the very center of a drill (the Web) does not cut (Or at least, it does a very poor job of cutting). When the Web is in contact with material, it can cause the drill to wobble.

But if the material has an existing hole, the drill bit will follow the hole PROVIDING that the drill bit is either new, or has been properly sharpened. If a drill bit has been IMPROPERLY sharpened, one side will contact the material before the other and cause a wobble

tommy157

My Feedback: (1)

Okay here is my $.02...I have always used a drill bit to drill prop hole. I need a 3/8" for my gasser so I clamp prop in vise , and let it find it's own center . I do balance my bigger props and last night I checked balance of a new 20X10 prop and balanced it before I drilled hole. Guess what? after drilling it was still balanced..maybe just luck but thats the results. If you want to use a reamer then go ahead but it appears it's just not necessary..

bingo field

I have a reamer also, but to drill out a prop without a drill press:
Clamp drill in vise
Spin prop down on drill
When prop bottoms on the top of the vise, done.
Check balance

This has worked for me. Maybe would check at a machine shop for really expensive equipment.
thanks

Bax

My Feedback: (11)

That's one reason why you need to use a center punch for accurate holes. The web can make the bit wander.

MinnFlyer

My Feedback: (4)

Exactly Bax

hookedonrc

At the risk of being more confused than I already am, I do have a question. Can you just take a reamer, and mount into the drill press? Seems to me you have the best of both worlds by doing this.

MinnFlyer

My Feedback: (4)

Sure you can

SamD

Skip the center punch; if you want to put a hole on location you start with a center drill followed by an undersize drill and then bore the hole (on location) and size the hole with a reamer. Then again, we're not jig-boring props so all that's a little overkill. As MinnFlyer points out, if there is an existing hole (what we'd call a "pilot hole" in the aircraft building industry) and the drill is properly sharpened, the drill will follow the hole. Add a improperly sharpened drill (which is common in the home shop when sharpening is done without a drill gauge) to the equation and bingo- you've got a mess on your hands. This all gets back to why boring (single point or boring-end mill) is the standard method for putting holes on location rather than drilling/reaming: drills and reamers will always follow an existing hole (providing they're new or properly sharpened). The thing about reamers: there's a limit to how much material they can remove so if you're trying to go from a 1/4" hole to 1/2", it's not going to happen (well, at least not successfully) whereas a drill will remove- for all practical purposes- the limit of its diameter.