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Thread: Tapered fitting to shaft
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22nd May 2019, 06:30 PM #1Senior Member
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Tapered fitting to shaft
My mate has a chipper/mulcher.
It threw a blade which bent the crank.
Removing the cutter disk from the crank, which is a taper fitting locked with an axial bolt proved extraordinarily difficult even with a gear puller. (bent the plate...)
The plate was off not long ago so I was surprised how difficult it was.
Even removing it after assembly (which was when the bend was found) was difficult.
He used grease on the shaft. Is this correct /ok/bad?
Russ
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22nd May 2019, 09:02 PM #2Most Valued Member
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It sounds a bit of a odd bod to me Russ, I lost count a long time ago of how many chippers that I have had to repair and they all had a parallel shaft and a key.
Generators have a tapered shaft and the odd pump may have also.
Typically you don't lube a taper as when you tighten the bolt that pushes the whatever onto the taper and it normally has a torque spec to push it on so far/tight and that would likely be dry unless otherwise specified.
So I think you need to hunt those details up, what make and model is it?
cheers, shed
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22nd May 2019, 11:21 PM #3Philomath in training
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I vaguely recall our mulsher (5hp Briggs and Straton) had a taper shaft on it.
Grease on the shaft would make it easier to push the tapered socket up the shaft for a given torque, so probably not recommended if you want to disassemble easily.
Michael
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22nd May 2019, 11:46 PM #4China
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If I were to put any thing on the taper I would use never seize
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22nd May 2019, 11:58 PM #5Golden Member
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G'day Russ,
When refitting aluminium flywheels on tapered lawnmower motor cranks I always dust the shaft with some graphite, this helps with smoother seating of the taper when torquing the retaining nut and makes them easier to remove next time.
Cheers,
Greg.
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23rd May 2019, 11:01 AM #6Most Valued Member
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When you assemble a shaft coupling it helps to undersand what is it actualy doing, how does it work......
Most of the forces on it are torsional, but in this instance you also have shock forces and vibrational forces and aslo significant enertia forces when these forces oppose each other.
So a tapered shaft coupling is basically 2 opposing tapers forced together with a nut or bolt to form a compression joint that relies on friction between the 2 mating tapers to transmit torque.
So what do you think will happen when you add a lubricant to this coupling that relies on friction to transmit torque?
If it is a part that needs to be removed often for maintenance then drill and tap a hole either side of the boss to utilize a puller that wont bend the blade carrier. Something that will put pressure on then a spot of heat and the taper will let go.
Dont go bashing the thing as you can crack the crankcase on the engine under the flywheel.
Cheers, shed
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23rd May 2019, 09:10 PM #7Senior Member
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Oops
My bad...brain freeze...
It is of course a straight shaft with keyway. I have no idea where the idea of a tapered shaft came from.
If it was a taper it would release almost immediately it moved but we had to use the puller almost the whole length.
Definitely impact load but it wasn't run after the blade was replaced, the bent crank was noticed and it was removed again. And seemed to be even tighter...
Russ
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24th May 2019, 11:43 AM #8Most Valued Member
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Russ it needs to be a fairly tight interferance fit otherwise the key and keyway will flog out.
It would likely also flog out if you put never seize on it, i have seen this a few times where mowing contractors put never seize on the disc bosses to aid in removal, they fairly soon become a sliding fit on the shaft and the keys and keyways flog out.
At installation i would just give it squirt of wd40 to help it slide on.
The cranks can be hard to hold to straighten depending on the orientation of the bend in relation to the balance weights.
I have also been able to straighten a couple with a strategic wack with a copper hammer, you dont do this with the crank in the engine.
If you need a crank there is a slim chance i might have one if it is a briggs engine???
Cheers, shed
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24th May 2019, 02:06 PM #9Golden Member
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I have removed a few taper fitting in the past with the homemade extractor. while the bolt on the extractor is under pressure, I use copper mullet to tap on the end of the bolt gently...
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24th May 2019, 06:42 PM #10Senior Member
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24th May 2019, 10:45 PM #11Most Valued Member
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25th May 2019, 12:27 PM #12Diamond Member
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25th May 2019, 01:28 PM #13Philomath in training
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The fish obviously. Getting hold of a bogan with red hair is difficult at the best of times.
Michael
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25th May 2019, 06:55 PM #14Most Valued Member
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