Reaming props
 

What is a better practice--

Using a prop reamer to go from the 3mm to 5mm +/- shaft size or is it ok to drill the hole out? (I've got a drill press)

The reamer is more accurate about just following the hole... but if you step up one drill size at a time the drill will follow the original hole just fine.

I do it both ways.

Balance the prop afterward either way.

I've also got a drill press and a whole assortment of number, fractional and letter drill bits. But those drill bits can very easily make the hole "Off Center".

What will work nicely is one of those prop reamers, modified to fit into your drill press. Use the drill presses lowest speed.

Thanks!

http://www.harborfreight.com/t-handle-reamer-66936.html

$2.99 at harbor freight. This is what I use. Never though to hook it up to the drill/drill press. My 480 motor has a 5mm shaft and prop adaptar, so I have to ream out the 11-12" apc props to get them over it.

I'm guessing its a 1/2" shaft, so it MIGHT fit in a 1/2" drill press/ drill chuck.

Reamer ........ then you know it's right.

Nigel

Agree drills will not work well. You will need the reamer.

I have had good luck drilling, and drilling then reaming with a taper-reamer, both ops carried out from the back of the prop. Done this for APC out to 5mm and 8mm.

You need to de-flash the front hub of the prop first, and I don't clamp the prop, I just set it on a clean piece of squared-up wood and hold one tip.

I set the drill-press to a very low speed, if it grabs I just let go.

More important you find a procedure that consistently works well for you than you use 'the best' procedure.

I keep looking at Pillar Drills in locakl shop .. but until I find one with a centring vice - I will hang back.
The Centring vice is the vice that fits the drill bed and is exact centre marked so a prop can be clamped and you KNOW it is centred. It is only way I would consider drilling now - having ruined too many props with drills.

The trouble is once the drill creates an offcentre even small amount - the drill bit in a pillar drill will actually deflect slightly to accommodate. The Reamer will not be able to correct it either. The only way to cure that is to use a hot-rod to MELT through a composite / plastic prop and then bush it back to required size. That's great for plastic ./ GFN / Composite - but what about wood ? Dunno for that ... I haven't used wood since I stopped doing Scale WW1 models !

Nigel

For BIG props there is a device to clamp in the hub and balance the prop by drilling the hole. Generally this turns out to be correcting a hole drilled off-center by the factory. (that does happen and is one reason we have to balance props)

If the hole is off center in a wood prop you have to clamp it in place in a drill press and clamp a drill guide on the prop to keep the bit from trying to follow the old hole.

It can be a lot of trouble to fix.
If the hole is off-center too much you have to drill oversize then dowel plug the hole then re-drill.
For props costing under $10 its usually not worth the time and effort, so you never see it done on small electric models.

Plastic and composite props are generally moulded - not drilled holes.

Balancing is not to correct misdrilled holes as holes are moulded - its to correct material distribution across the prop construction. It's impossible for moulding to have perfect density stabilisation of material throughout the prop.

Nigel

Found mine at LHS. Best invention since the wheel !

I'm building a tri-copter and my motors currently are configured to where I need to use the prop spinner (supplied w/motor) that bolts to the housing. The 3mm shaft extends out the side with the power leads. I suppose I could pull the c-clip and take the motor apart and push the shaft thru the other side. Then I could use props I have w/3mm hole. Otherwise I need to ream/drill them out to fit the spinner. I was trying to avoid opening up 3 new motors but I suppose I could.

While the vast majority of small electrics use plastic props... There are some very good wood E-rated props available appropriate for planes appx 1 lb and up.

The APC grey composites are some of the most efficient props on the market and wood ones are less efficient every time, but the wood ones can often be better than the GWS and many other plastic props.

Also any prop rated for glow/gasoline can be used for electric. the electric props don't have to be as strong, but you might desire to go with a "glow" style prop for appearance
Or for resisting minor tip strikes with the ground. Master Airscrew black/grey composite props are excellent. (less efficient than most wood e-rated or glow rated props... good paint stir-sticks)

There is a growing assortment of good props for electric... but I find myself still hand re-carving glow rated wood props occasionally to get exactly what I want.

there are two fields that Wood props win hands down ..

a) Cosmetic appeal on old-timer models such as WW1 etc.

b) They are most stable in form when in use - they do not deform like most plastics - even composites.

Sadly one of the best performing props have been discontinued many years ago - Taipan. We used them for Club 20 Pylon racing ... then when they started getting harder to source - the Master Airscrew GFN took over.

GFN = Glass Filled Nylon This is the most stable and stiffest plastic composite prop.

Nigel

My reason for my initial question was because of a current project--a tricopter. The 3 motors I have on hand will require me to use the included 3mm to 5mm prop adaptor. I have a pretty good supply of props on hand but they're all for a 3mm shaft so in order to try to utilize them I would need to ream the prop hole. Was in my LHS today, went ahead and picked up the Great Planes prop reamer. I'm glad I throw away all my rc receipts both there and from online purchases. If I verified what I think I've spent since this time a yr ago I'd probably be sick. ::o

Another idea ... can you cut a thread on the 3mm shaft ? Then you never need to ream another prop for that model again.

Or order a replacement shaft that is threaded at end ... Skyartec 182 motor uses a 3mm threaded shaft ... and is cheap to buy shaft ...

Many props that are 3mm - have insert into shaft hole that prop nut goes into ... fits the 3mm threaded shaft perfectly.

But now you have the Reamer ....... it's good for many more things than just reaming props. Angled to a surface - that cutting edge will slice through surprising thickness. The point gives a great starting hole for screws. You can create holes for pins etc - slowly opening them up till get good fit Etc etc.

Nigel

Good question. I've been flying various Hacker motors, and also have a few of those cheap motors. The Hackers have hard steel shafts, making it very difficult or not possible to cut threads on them.

Two of the cheap motors also have hard steel shafts. Quick way to find out which is which is to lightly run a fine file against the shaft. If the shaft is made from hard steel, it will be apparent. Compare that against running the file against a common nail.

The other point is that most shafts are case hardened - NOT fully hard all way through.

Good point - never cut a shaft thread - I've always done the alternative by swapping out shaft ...

Nigel

You're right, a steel shaft hard all the way though could be as brittle as a piece of glass. :D

No, don't use that use one of these instead.

http://www.rcplanet.com/ProductDetai...Fc9AMgode2QAWQ

Personally I would avoid any Stepped Reamer for good reason.

Sooner or later a Reamer needs to be sharpened. The edge blunts. With a Stepped Reamer as you link to - as soon as you start sharpening - you reduce its size. But a Tapered Reamer... you can sharpen as much as needed and you will always be able to achieve the hole size ...

Second - a Tapered Reamer will ream to fit a shaft even when shaft is not exactly sized as stated ... it can be used to ream from 0.000x up to xxmm without need to buy a second or extra to cater for other sizes, as with a Stepped Reamer.

Nigel

I have a comment which no doubt will start all the APC online quotes / cut and pastes etc ..... but here goes :

The OP wants to go from 3mm to 5mm ... which is quite a jump for a small prop and if reamed purely from the rear as per APC - could lead to grossly oversize extreme rear hole and possibly weak prop boss. Reaming from rear when it's only a 1 size up etc. is fine as plenty of 'meat' is left in the boss.
Personally when a large increase is needed - then I ream from both sides to reduce the amount the reamer has to enter rear to get front to correct requirement. This then means I retain maximum 'meat' to my prop boss.

Nigel

Hopefully the stepped reamer uses steel that won't get dull when reaming a plastic prop. :D :D

Good point though, the stepped reamers don't come in metric sizes, at least in the USA.

Nigel your point is one of my concerns. I don't want to remove so much material that I grossly decrease the strength in the prop boss. I have ordered a handful of the props that I think I'll need in case the props I have on hand won't work out well.

I really appreciate all the good points all of you have raised.

Wayne