Thread a 1/8" prop shaft - which is the correct die to use

[KTM_EXC]

Hi everybody,
I'd like to thread a 4mm. prop shaft in order to use 1/8" drive dog props (usually I use M4 props); it’s a custom made prop shaft as I should couple it with a 1,5 mm. spring wire and I cannot find this measure on the market.

Is there a specific 1/8" die to choose?
I found these:
ME die = Model Engineer die or Model Engineering dies in 40tpi = threads per inch --> http://www.tap-die.com/contents/en-u...tpi_40tpi.html
MTP die = MTP die = Model Taper Pipe dies or METP = Model Engineering Taper Pipe die dies in 56 tpi = threads per inch --> http://www.tap-die.com/contents/en-u..._MTP_dies.html

Which is the wright choice; first, second, none of them?

Many thanks
Cheers
Andrea

[J.W. Pepper]

Hi everybody,
I'd like to thread a 4mm. prop shaft in order to use 1/8" drive dog props (usually I use M4 props); it’s a custom made prop shaft as I should couple it with a 1,5 mm. spring wire and I cannot find this measure on the market.

Is there a specific 1/8" die to choose?
I found these:
ME die = Model Engineer die or Model Engineering dies in 40tpi = threads per inch --> http://www.tap-die.com/contents/en-u...tpi_40tpi.html
MTP die = MTP die = Model Taper Pipe dies or METP = Model Engineering Taper Pipe die dies in 56 tpi = threads per inch --> http://www.tap-die.com/contents/en-u..._MTP_dies.html

Which is the wright choice; first, second, none of them?

Many thanks
Cheers
Andrea

Andrea, not sure if this info will help you, but here it is in case it will...

I got one of these shafts from Steve (OSE) for my Trax Blast... http://www.offshoreelectrics.com/pro...od=oct-ocgcss4 - stock shaft has 4mm threaded prop, the Octura shaft converts it to 1/8" smooth bore so I can use standard props.

On page 10 of the Octura catalog it says that shaft uses a OC4PN prop nut, on the same page it describes that part as follows... Prop Tail Nut - Streamlined - fits 5-40 thread on 1/8" shaft - brass - 7/32" hex - 9/16" long.

Top of page 11 same catalog it says that shaft uses a OC4D drive dog - 1/8" I.D. - 1/4" diameter - with 4-40 set screw - brass

Good luck

[KTM_EXC]

I've seen the shaft; outer dimensions are fine; the problem is that it fits flex cables; in my case I should use with 1,5 mm piano wire. Do you know if it's available without the shaft hole?
Thx
Andrea

[KTM_EXC]

I've seen the shaft; outer dimensions are fine; the problem is that it fits flex cables; in my case I should use with 1,5 mm piano wire. Do you know if it's available without the shaft hole?
Thx
Andrea

[Basstronics]

Are you from MI? Why are you looking at a UK site?

1/8 standard prop shafts have a #5-40 thread. The second one you listed is a tapered pipe thread, which you dont want.

You wont find a wire drive with a metric wire and a standard nut. So you will need to have this special made. Jeff Wohlt can probably make this for you.

[KTM_EXC]

Hi,
MI means Milano (Italy) not Minnesota
Thanks for the confirmation 5-40 is fine

[NativePaul]

I've used M3 threads on the tail end of 1/8th" stub shafts due to the lack of 1/8th" locknuts in the UK, it is a little smaller but that is fine as long as you are not trying to seat the prop on the treads (which is a bad idea whatever the size), the threads will still cut OK as long as you go slow and back out often.

[KTM_EXC]

i've used m3 threads on the tail end of 1/8th" stub shafts due to the lack of 1/8th" locknuts in the uk, it is a little smaller but that is fine as long as you are not trying to seat the prop on the treads (which is a bad idea whatever the size), the threads will still cut ok as long as you go slow and back out often.

thx

[J.W. Pepper]

I've seen the shaft; outer dimensions are fine; the problem is that it fits flex cables; in my case I should use with 1.5 mm piano wire. Do you know if it's available without the shaft hole?
Thx
Andrea

Don't know where your getting your info from but it is not for flex cables! The Traxxas Blast has a solid drive shaft that is connected to the prop shaft with a universal joint - http://traxxas.com/products/models/marine/3810blast - goto gallery and look at the pictures. If you download the parts diagram it can also help you.

And now that I know your in Italy I'll go metric with all measurements. The stock Traxxas prop shaft is for 4mm threaded props, the European standard.

The Octura shaft is aimed at the American standard where we use smooth bore props held in place with a drive dog and prop nut. It is a solid piece of steel - round stock .156" (3.96240mm) in diameter; I measured it with my Starrett dial caliper. It was too long when I received it, I had to cut some material off and create a flat spot for the universal joint grub screw to lock onto.

If you mount it into a drill press or a mill, you can drill a 1.5mm hole in the none prop side to insert the piano wire into; that will leave you with 2.4624mm wall thickness. I would suggest brazing the wire to the shaft for strength.

Hope that clarifies any misunderstandings / confusion.

[NativePaul]

If you mount it into a drill press or a mill, you can drill a 1.5mm hole in the none prop side to insert the piano wire into; that will leave you with 2.4624mm wall thickness. I would suggest brazing the wire to the shaft for strength.

Good luck getting the hole centred with that technique, a lathe (and a well set up one at that) is the only tool for that job in my opinion. You better do some research on heat treatment too, as spring steel piano wire sure isn't going to be very springy after you get it hot enough to braze it, unless you do some work on it afterwards.

Consider using 1.6mm piano wire (which is interchangable with .062") instead of 1.5mm if you cant find exactly what you are looking for, I think Model Marine supplies in the UK or Wohlt's RC Boats in the USA could both do it in that size.

[J.W. Pepper]

Good luck getting the hole centred with that technique, a lathe (and a well set up one at that) is the only tool for that job in my opinion. You better do some research on heat treatment too, as spring steel piano wire sure isn't going to be very springy after you get it hot enough to braze it, unless you do some work on it afterwards.

Consider using 1.6mm piano wire (which is interchangable with .062") instead of 1.5mm if you cant find exactly what you are looking for, I think Model Marine supplies in the UK or Wohlt's RC Boats in the USA could both do it in that size.

Drill press, ok I'll go with you on that, but why not a mill?? I would think that it would be just as accurate as a lathe.

Since brazing isn't an option - for the reasons you correctly pointed out - how do you keep the wire from coming loose from the shaft?? Epoxy??

I've never heard of Model Marine supplies, but I know Jeff Wohlt is considered "the man" for wire drive setups here in the states.

[Basstronics]

No not even a mill. The setup time to get it somewhat accurate is stupid insane. Even at that it wont be as accurate. If you dont have a lathe with a collet then you dont have the right tool for the job, period. Unless you are turning the shaft down from a larger diameter.

We use Loctite 648 or similar for filling radial gaps up to .010". Items must be roughed up and extra clean/dry before gluing or you WILL have failure.

[J.W. Pepper]

No not even a mill. The setup time to get it somewhat accurate is stupid insane. Even at that it wont be as accurate. If you dont have a lathe with a collet then you dont have the right tool for the job, period. Unless you are turning the shaft down from a larger diameter.

We use Loctite 648 or similar for filling radial gaps up to .010". Items must be roughed up and extra clean/dry before gluing or you WILL have failure.

We use Loctite 648 or similar for filling radial gaps up to .010"... Thank you!!, I'll log that one into my "I need to remember that tip" book.

[NativePaul]

The only way to find true center with a mill would be to use a CNC mill and turn a block down into a 4mm stub, in which case the computer will know exactly were the centre is, but still it is unlikely that the centre will fall exactly on the step of the stepper motors so even then there is bound to be runout to some extent.

I have heard of people using silver solder which has a lower melting point than braizing, but I wouldn't risk it myself, everyone I know that makes wires uses Loctite bearing retainer, either 603 or 638, personally I use 603 as it is oil tolerant and although I clean it out as best I can with acetone I am paranoid about traces of cutting fluid remaining in the hole, 638 is stronger but not oil tolerant, I have had a couple of wires snap but not a joint let go yet so I am happy with the strength of 603.

I don't know anyone else using 648, but I had a look at the datasheet and it is an interesting choice, same strength as 603, and with a much quicker cure, it might be worth my investing in a small bottle for field repairs, after one wire has been in there I am more confident about it being oil free.

[KTM_EXC]

Thank to everybody for your support.
I'll make it with a lathe; prop shaft will be used in a SAW rigger so it should be done the best I can.
I will couple with spring wire using Loctite 648; in my experience if you burn both on a gas flame for few seconds and then degrease with acetone Loctite works perfectly.