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[dillinger 04]

Hello Everyone




I am looking for the best tools for cutting roughly 4mm wide by 15 mm long rectangular slots in 4mm birch plywood for a prop shaft opening.
small hobby saws designed of cutting plywood? or other tools that might do the job . Any help would be appreciated   

[Footski]

I would drill a hole in one corner and then use a small saw blade to make the cuts..filing down the edges once the hole is cut.

[SteamboatPhil]

Urm have you got that right, a 4 mm slot in 4mm material....

[6705russell]

I think he means 4mm thick plywood Phil not 4mm wide..

[Mark T]

I would drill a hole in one corner and then use a small saw blade to make the cuts..filing down the edges once the hole is cut.

Great advice  - this is what I would do

[derekwarner]

Considering this slot is for a prop shaft, the suggestion from Footski...of starting with 'a hole at either end makes absolute sense, as the entry/exit geometry of the shaft through the hull is an ellipse


If the slot is 4mm wide, using a 4 diameter drill...and so if the slot is 15 long, have the slot drill centers @ ~~11 mm  .....  


[allows for feathering or tapering in/out]


Derek

[Tug Fanatic]

4mm is a very narrow propshaft!

[Colin Bishop]

4mm is normal for a shaft but the tube is usually 6mm or 8mm in diameter.

Colin

[malcolmfrary]

The only times that I have used a prop shaft requiring a hole that small has involved plastic kit conversions and building my own prop shaft assembly, and they have always been a straight simple hole in a prepared spot.  If this is for anything other than a very small model (and 4mm ply says not), then it would normally want, as Colin says, a prop shaft assembly with a 6 or 8mm outside diameter tube. 
Use a drill of the right diameter, drill in the centre of the shaft exit, when a hole is created, twist the rotating drill to elongated the hole with the splines of the spinning bit until you have one the right shape to accept the tube at the angle wanted.  The tube will need fixing in place, epoxy does that while at the same time sealing round the tube.

[chas]

I've just re read the original post, it says roughly 4 mm slots, presumably in sheet material. This, to me sounds like slots in frames to go over an installed prop shaft and tube.
  Whatever the slots are for, most people would use a hacksaw, with a fine toothed blade, then cut a little undersize, and file out for a good snug fit. Just like slots in bulkheads to go over a keel.
Charles

[Tug Fanatic]

4mm is normal for a shaft but the tube is usually 6mm or 8mm in diameter.

Colin

Yes I was thinking of the whole propshaft assembly rather than just the shaft itself. Personally I would still want more than a 4mm hole for a 4mm shaft if at all possible.