RC54 mower deck center blade won't torque down, and blade speed not matching spindle speed

[rustythread]

RC54-??? (part of label missing) on B7200 HST. With the splined fitting and the 2 Belville washers and blade in place, and the blade bolt torqued down, the blade is still just loose enough that blade speed does not match spindle speed. Natch, gets hot as hell when trying to mow.
The Belville (cup spring) washers are probably as old as the tractor and would be my first suspects, but there does not seem to be any difference when I swap the blades, washers, and splines from one spindle to another. Grass is getting higher while I try to figure this out. Driving me half-nuts.

I may replace all six of the Belvilles if somebody can suggest a place to get them at a reasonable price, even if that is not a source of the present problem.

 

[85Hokie]

Take the bolt out - and take flashlight and see if there is anything compacted in the threads....maybe a pick or small screwdriver and see if anything is there up in the spindle threads.

Look at the threads on the bolt carefully - any place worn in the grooves? On one of mine it was a cause of this problem

also - take the bolt and run it up and back and see if IT Is stopping in some boogered up threads - maybe with a little oil to help it move freely.

It may be hitting a spot and not flattening out those washers.

Last thing - take another washer and place it on the bolt FIRST and then place the next cupped washers down and torque ...... see if this makes any difference at all.

 

[rustythread]

Take the bolt out - and take flashlight and see if there is anything compacted in the threads....maybe a pick or small screwdriver and see if anything is there up in the spindle threads.

Look at the threads on the bolt carefully - any place worn in the grooves? On one of mine it was a cause of this problem

also - take the bolt and run it up and back and see if IT Is stopping in some boogered up threads - maybe with a little oil to help it move freely.

It may be hitting a spot and not flattening out those washers.

Last thing - take another washer and place it on the bolt FIRST and then place the next cupped washers down and torque ...... see if this makes any difference at all.

Thanks, 85Hokie!

No crud in bolt hole, and bolt goes in all the way with no difficulty.

I took your suggestion and put on a washer first, then the conical spring washers and blade. Seems tight; will see when the rain stops.

Still thinking about replacing all the conical spring washers ("blade retainers" on the Kubota parts lists). Anybody have any experience re the quality of replacement parts from either Stens or Stevens Lake Parts?

 

[BruceP]

I had to replace my Belleville washers... they loose their tension over time. I ordered real Kubota replacements.

The HEAT you speak of will instantly destroy the temper on Belleville washers and even wear down other parts. Consider replacing ALL the components that hold the blades on.

I am assuming you are using KUBOTA blades.... Aftermarket blades may not have the same thickness (be too thin) and contribute to slippage.

 

[rustythread]

I had to replace my Belleville washers... they loose their tension over time. I ordered real Kubota replacements.

The HEAT you speak of will instantly destroy the temper on Belleville washers and even wear down other parts. Consider replacing ALL the components that hold the blades on.

I am assuming you are using KUBOTA blades.... Aftermarket blades may not have the same thickness (be too thin) and contribute to slippage.

Thanks for your info and advice.
IIRC the blades have the Kubota part numbers on them. It is only the center assembly which has the problem--the two outside blade / hub assemblies are fine.
I have ordered all new Belleville washers and a replacement center bolt.

 

[lugbolt]

The HEAT you speak of will instantly destroy the temper on Belleville washers and even wear down other parts. Consider replacing ALL the components that hold the blades on.

I am assuming you are using KUBOTA blades.... Aftermarket blades may not have the same thickness (be too thin) and contribute to slippage.

yup I replace them on every mower I service....have to....liability concerns. And torque the blades, with a calibrated torque wrench of which "I" (the tech) have to pay for, out of my own pocket. A $270 torque wrench (now over $530!) and pay the tool people $52 3 times a year to check and/or calibrate it. They say a tech is nothing but a parts changer....but most don't understand what goes on behind the doors that you can't see through.

LOTS of DIY'ers put the cone springs on backwards, upside down, on the wrong sides of the blade, etc. Blades on upside down frequently too. See it all the time. Then you got guys that absolutely refuse to buy Kubota blades, yet they'll order a set of Gators or really any aftermarket blade set off of Amazon, pay the same amount of money, and find out that they're thinner....which causes the blade to fail to tighten up properly, it slips, takes out the spindle, bolt, both cone washers, boss, everything....so much for saving $5. some of the newer mowers have even more parts than the older stuff...boss, bunch of washers, another boss/spacer, etc etc. Not even mentioning that they are not balanced, brand new, out of the package I usually have to grind them a little to get them to balance--brand new blades, then have to repaint them so that the owner/purchaser doesn't get all upset that we had to grind new blades.

One of the things I seen recently was a set of aftermarket blades advertised as a certain thickness and a certain percentage thicker than OEM. But what they don't tell you is that the paint (powder coat?) that they use is really thick so that when you measure the thickness with your $5 digital caliper, they "are" thicker. Grind the paint off and they're considerably thinner if you measure the metal. On a lot of kubota's the blade washers are so very important that they MUST be there, and the thickness of the blade is critical. When that big thick paint layer wears off, the blade loosens up, slips some more, and the whole ordeal becomes a heap of learning experiences. BTDT!

 

[Dave_eng]

Thanks for your info and advice.
IIRC the blades have the Kubota part numbers on them. It is only the center assembly which has the problem--the two outside blade / hub assemblies are fine.
I have ordered all new Belleville washers and a replacement center bolt.

I am with Lugbolt on this subject.

My experience is that once a blade starts to rotate by slipping, the blade center hole wears enough that the blade will not be centered and rotating not centered generates large imbalance forces which loosen the retaining bolt. Removing the paint film where the clamping hardware will seat is also a good idea.

It usually takes new hardware including a blade to stop this from happening once it starts.

Dave

 

[rustythread]

es seem to be some slop
I am with Lugbolt on this subject.

My experience is that once a blade starts to rotate by slipping, the blade center hole wears en ough that the blade will not be centered and rotating not centered generates large imbalance forces which loosen the retaining bolt. Removing the paint film where the clamping hardware will seat is also a good idea.

It usually takes new hardware including a blade to stop this from happening once it starts.

Dave

.
Dave, you may have hit it on the head. I tried mowing today after taking up the vertical slack by adding a washer. About three minutes in, I could see that the center blade was once again cutting poorly. There does now seem to be some slop in the blade center hole. Looks like I'm up for new blades and a couble more blade bolts. There's some grooving on the outside of the internal-splined fitting, too. Think I ought bite the bullet and replace that now, too?

 

[Dave_eng]

.
Dave, you may have hit it on the head. I tried mowing today after taking up the vertical slack by adding a washer. About three minutes in, I could see that the center blade was once again cutting poorly. There does now seem to be some slop in the blade center hole. Looks like I'm up for new blades and a couble more blade bolts. There's some grooving on the outside of the internal-splined fitting, too. Think I ought bite the bullet and replace that now, too?

Any time you have relative movement in parts that are intended to live their lives together motionless relative to each other, wear is occurring and it does not take much wear to mess up the centering action needed to sustain high speed rotation.

The same thing happens on cars and trucks where a wheel comes loose once and then, despite being properly torqued the next time, continues to come loose or even come off. The amount of wear needed to affect future retention performance is quite small.

Dave

 

[GeoHorn]

I ran into a similar problem with my aftermarket finish mower... the center blade was slipping. I tried tightening the bolt and that didn’t fix it.
New blade, new bolt, new washer..... VOILA!

 

[rustythread]

I ran into a similar problem with my aftermarket finish mower... the center blade was slipping. I tried tightening the bolt and that didn’t fix it.
New blade, new bolt, new washer..... VOILA!

Thanks for the info.
I have gone ahead and ordered all new spring washers, all new blades, and one blade boss. I'm also hoping that my effort to cancel my prior order works--I had misread the diagram and ordered the wrong parts the first time ( I have only 5% vision, which makes for lots of adventures).

 

[rustythread]

Replaced all 3 blades, all six Belleville washers, and the lower blade boss on the center shaft. Have mowed about 2 acres since, and all seems well.
Thanks to all for the info and suggestions.

 

[JeepinMaxx]

Glad it all worked out! Do you happen to have the part numbers for the washer and bolt?

 

[Dave_eng]

Replaced all 3 blades, all six Belleville washers, and the lower blade boss on the center shaft. Have mowed about 2 acres since, and all seems well.
Thanks to all for the info and suggestions.

Thanks for the update. This will help others in the future!!

Dave

 

[rustythread]

Glad it all worked out! Do you happen to have the part numbers for the washer and bolt?

The Belleville washers, listed as retainers on the parts diagram, are part # 76550-25004; blade bolt is # 76539-34372; lower blade boss is 76539-34392. Mower deck is an RC54-B

 

[JeepinMaxx]

The Belleville washers, listed as retainers on the parts diagram, are part # 76550-25004; blade bolt is # 76539-34372; lower blade boss is 76539-34392. Mower deck is an RC54-B

Thank you!