Failed to remove the shaft coupling

Lucas Gan

Active member
Joined
5 Oct 2018
Messages
473
@fisherman The spacer is 25mm in diameter only. So it's not covered the key.

@TheCoach I checked again. There are no any more screw whatsoever. The screw hole can see the shaft clearly.


I am thinking of grinder cut the coupling now after almost one more hour trying to free the stuffing box nut but failed.
 
Last edited:

stelican

Well-known member
Joined
25 Nov 2004
Messages
2,291
Location
fareham hampshire
It would be very unlikely but has the coupling been slid along the shaft from the prop end, But perhaps not as you say the end of shaft in coupling is 45mm.
 

TheCoach

Active member
Joined
10 Oct 2019
Messages
137
If it had then the key could be tapered so you are pulling it tighter?

Couple of hefty blows on the flange when its hot to see if it will move down the shaft and release the key?

Would this damage anything further down the shaft?

TC
 

fisherman

Well-known member
Joined
2 Dec 2005
Messages
16,564
Location
Far S. Cornwall
This is a longshot: in #36 the key looks like it has two flats and two rounded sides: I've seen a case where a tapped hole was drilled in the shaft/coupling interface with a screw in it. If that is a screw you may need to give the coupling a tap towards the shaft to release pressure. (Also, looks like a second keyway on the near side of the coupling, but not in the shaft, in the pic)
 

Lucas Gan

Active member
Joined
5 Oct 2018
Messages
473
Ok. I am going to practice a bit my grinder skills in the back garden as I never used a grinder before.

Open my new bosch grinder box, found no disc in it! Have to go to buy a disc before training.
 

seastoke

Well-known member
Joined
16 Mar 2013
Messages
8,616
Location
boat conwy
Ok. I am going to practice a bit my grinder skills in the back garden as I never used a grinder before.

Open my new bosch grinder box, found no disc in it! Have to go to buy a disc before training.
There are different discs get the very thinnest you can , and get a few.
 

Caraway

Well-known member
Joined
11 Aug 2019
Messages
6,091
Location
England
Ah.

I don't use the safety guard as that usually stops you getting to where you need to be. (That's me. I am not recommending that)
Always wear safety goggles or a visor (but visors mist up)
Always wear leather gloves.
Always hold it with two hands.
Don't try to start the grinder with the blade already in the cut (it can grab and jump out of your hand. Don't try to catch it!)
Don't use the switch lock, it can keep on running if things go wrong.
Don't stand in line with the radial axis of the disc (if it breaks it will stab you with lots of little bits of disc.)
Always cut with the rotating edge of the disc that is spinning towards you. Which means the appliance is trying to move away from you. (If you touch the disc to the work piece and it tries to drive the appliance towards you, you are a target).
Don't put it down before it has stopped spinning.

Bound to be things that people disagree with, but that has kept me safe for a few decades.

On the discs . Get 1mm discs and pay more than you need to. Most cheap discs blow away to powder and if they get damp will crack when they heat up. (multi pack discs in Big Sheds are usually rubbish)
115mm discs will fit inside the guard. 125mm discs probably won't.
Get metal cutting discs, not stone.
Stainless steel, Inox discs are usually what they are called. Screwfix sell a range some branded like Bosch and DeWalt. I have been using their Norton discs without any failures.
 
Last edited:

fisherman

Well-known member
Joined
2 Dec 2005
Messages
16,564
Location
Far S. Cornwall
Before you go mad, just try to turn the key with a spanner. the more I look at it the more likely it seems, the key is left proud, but not enough to foul the male register on the gearbox side. The old keyway is visible, new shaft installed, drilled and tapped instead of a key. It's a method used in PTO couplings.
 

Scala

Well-known member
Joined
21 Feb 2004
Messages
4,682
Location
Home: Saffron Walden. Boat: Swanwick
Before you go mad, just try to turn the key with a spanner. the more I look at it the more likely it seems, the key is left proud, but not enough to foul the male register on the gearbox side. The old keyway is visible, new shaft installed, drilled and tapped instead of a key. It's a method used in PTO couplings.
You mean that the end of what looks like a key is actually the head of a machine screw?
 

cherod

Well-known member
Joined
2 Dec 2018
Messages
5,010
Ah.

I don't use the safety guard as that usually stops you getting to where you need to be. (That's me. I am not recommending that)
Always wear safety goggles or a visor (but visors mist up)
Always wear leather gloves.
Always hold it with two hands.
Don't try to start the grinder with the blade already in the cut (it can grab and jump out of your hand. Don't try to catch it!)
Don't use the switch lock, it can keep on running if things go wrong.
Don't stand in line with the radial axis of the disc (if it breaks it will stab you with lots of little bits of disc.)
Always cut with the rotating edge of the disc that is spinning towards you. Which means the appliance is trying to move away from you. (If you touch the disc to the work piece and it tries to drive the appliance towards you, you are a target).
Don't put it down before it has stopped spinning.

Bound to be things that people disagree with, but that has kept me safe for a few decades.

On the discs . Get 1mm discs and pay more than you need to. Most cheap discs blow away to powder and if they get damp will crack when they heat up. (multi pack discs in Big Sheds are usually rubbish)
115mm discs will fit inside the guard. 125mm discs probably won't.
Get metal cutting discs, not stone.
Stainless steel, Inox discs are usually what they are called. Screwfix sell a range some branded like Bosch and DeWalt. I have been using their Norton discs without any failures.
thats all sound advice ,, yoo nows yer grinding (y)
 

Falling Star

Member
Joined
4 Mar 2011
Messages
526
Location
Essex
Ah.

I don't use the safety guard as that usually stops you getting to where you need to be. (That's me. I am not recommending that)
Always wear safety goggles or a visor (but visors mist up)
Always wear leather gloves.
Always hold it with two hands.
Don't try to start the grinder with the blade already in the cut (it can grab and jump out of your hand. Don't try to catch it!)
Don't use the switch lock, it can keep on running if things go wrong.
Don't stand in line with the radial axis of the disc (if it breaks it will stab you with lots of little bits of disc.)
Always cut with the rotating edge of the disc that is spinning towards you. Which means the appliance is trying to move away from you. (If you touch the disc to the work piece and it tries to drive the appliance towards you, you are a target).
Don't put it down before it has stopped spinning.

Bound to be things that people disagree with, but that has kept me safe for a few decades.

On the discs . Get 1mm discs and pay more than you need to. Most cheap discs blow away to powder and if they get damp will crack when they heat up. (multi pack discs in Big Sheds are usually rubbish)
115mm discs will fit inside the guard. 125mm discs probably won't.
Get metal cutting discs, not stone.
Stainless steel, Inox discs are usually what they are called. Screwfix sell a range some branded like Bosch and DeWalt. I have been using their Norton discs without any failures.
Yes to all that. Plus, use some ear defenders.
Noisy things, grinders.
You could be there a while.............
 

Lucas Gan

Active member
Joined
5 Oct 2018
Messages
473
Maybe it's the key stopping it comes off. I tried to hammer the coupling into the shaft forward to the propeller direction to see if that can get the key out. But no use. The coupling just no any movement no matter how hard I hammer it. I am now going to order the 10 pack Bosch 115mm cutting disc.

Is this fit the job?
Bosch Metal Cutting Discs 4½

Many thanks.
 

Scala

Well-known member
Joined
21 Feb 2004
Messages
4,682
Location
Home: Saffron Walden. Boat: Swanwick
Maybe it's the key stopping it comes off. I tried to hammer the coupling into the shaft forward to the propeller direction to see if that can get the key out. But no use. The coupling just no any movement no matter how hard I hammer it. I am now going to order the 10 pack Bosch 115mm cutting disc.

Is this fit the job?
Bosch Metal Cutting Discs 4½

Many thanks.
Did you try @fisherman suggestion of getting a spanner on the end of the key and try to unscrew it?
 

burgundyben

Well-known member
Joined
28 Nov 2002
Messages
6,639
Location
Niton Radio
Cool. That’s an interesting idea.
There must be something there stopping this coming off. Kudos to @Lucas Gan for perseverance!
I'm not convinced we (Lucas or people on this forum) understand the joint.

What takes the fwd thrust?

Lucas says its not a taper.

So it must be parallel.

Interference fit? I've never seen one, how would the boat buikder have assembled it?

Grub screws? Do they penetrate into the shaft?

The key to getting the [Inappropriate content removed] off is understanding the joint and how it was put together.

Or Lucas needs big boy pants and go banjax with the grinder. Shame to wreck the shaft.
 
Last edited by a moderator:

stelican

Well-known member
Joined
25 Nov 2004
Messages
2,291
Location
fareham hampshire
Probably missed something here but why do you need to replace the stuffing box?
Will you be doing both sides?
If so maybe the other side might come apart easier and answer a question.
 
Top