Bush hog blade blues

[texican]

Thanks for any advice.

First tractor/brush cutter, had it about two years. Done a good bit of maintenance on tractor now I thought it was time to get the cutter some love. Its a 93 M&W (absorbed by Rhino if what I read is accurate). So the blades, which I assume to be the originals had chunks missing and were rounded off and dull. I bought new blades, ran the existing nuts all the way down with my 2 gallon compressor that is used for airing up tires and pool toys.

Took the tractor to the farm (rookie move not engaging the new blades at home where all my tools are just to see how she ran) , an hour away, engaged the blades and the cutter shook like you wouldn't believe, well maybe this has happened to you and you would actually believe. Looked up under the cutter and tried to spin the blades and they wouldn't move. The were stuck in whatever position they were in when I ran the nut all the way down with my 4gallon 200 psi job site compressor from HF, would not rotate at all.

Got on the forum and the consensus was I shouldn't have cheaped out and should have bought the new bolts and washers to go with new blades. (I agree, that was super cheap not to). A cpl of guys told me the shoulder of the bolt would/should/might be different than the original ones I reused. Even if not, I def should replace the bolts that have been in the cutter since 1993. I was/am in totally agreement.

I got the bolts/washers and put them on. Now, using same compressor, I can only get them about 60% -65% on. Everything is the same but the nuts/washers. I went too hard on that small compressor and could smell it. I had condensation coming out of the wrench end of the hose. Wont turn anutha furtha. The blades have a lot of up and down play due to the bolt still having plenty to go.

This weekend, I took 1/2 ratchet and an extension and and had my wife hold pressure down on it while I tried to get it turn with an 8ft cheater pipe..I thought either the extension, the chinese impact 1 5/16 impact socket or my granddad's 1960s Craftsman ratchet was going to break. Tried it several times just up to the breaking point..nothing. I even soaked the nuts in penetrant for about 5-6 hours while doing some other work.


So, was I able to run the original nuts down on the new blades with my small compressor because they threads were worn down or something. Visually, I see no difference.

FYI.. the new and old bolts look identical in every way. I've tried to find the slightest difference to explain this and I see no differences at all.

What is my next move, to take it into a tractor shop or mechanic shop and see if thet can run it down with a much bigger compressor?

Thanks for any direction on this.

 

[SDT]

Thanks for any advice.

First tractor/brush cutter, had it about two years. Done a good bit of maintenance on tractor now I thought it was time to get the cutter some love. Its a 93 M&W (absorbed by Rhino if what I read is accurate). So the blades, which I assume to be the originals had chunks missing and were rounded off and dull. I bought new blades, ran the existing nuts all the way down with my 2 gallon compressor that is used for airing up tires and pool toys.

Took the tractor to the farm (rookie move not engaging the new blades at home where all my tools are just to see how she ran) , an hour away, engaged the blades and the cutter shook like you wouldn't believe, well maybe this has happened to you and you would actually believe. Looked up under the cutter and tried to spin the blades and they wouldn't move. The were stuck in whatever position they were in when I ran the nut all the way down with my 4gallon 200 psi job site compressor from HF, would not rotate at all.

Got on the forum and the consensus was I shouldn't have cheaped out and should have bought the new bolts and washers to go with new blades. (I agree, that was super cheap not to). A cpl of guys told me the shoulder of the bolt would/should/might be different than the original ones I reused. Even if not, I def should replace the bolts that have been in the cutter since 1993. I was/am in totally agreement.

I got the bolts/washers and put them on. Now, using same compressor, I can only get them about 60% -65% on. Everything is the same but the nuts/washers. I went too hard on that small compressor and could smell it. I had condensation coming out of the wrench end of the hose. Wont turn anutha furtha. The blades have a lot of up and down play due to the bolt still having plenty to go.

This weekend, I took 1/2 ratchet and an extension and and had my wife hold pressure down on it while I tried to get it turn with an 8ft cheater pipe..I thought either the extension, the chinese impact 1 5/16 impact socket or my granddad's 1960s Craftsman ratchet was going to break. Tried it several times just up to the breaking point..nothing. I even soaked the nuts in penetrant for about 5-6 hours while doing some other work.


So, was I able to run the original nuts down on the new blades with my small compressor because they threads were worn down or something. Visually, I see no difference.

FYI.. the new and old bolts look identical in every way. I've tried to find the slightest difference to explain this and I see no differences at all.

What is my next move, to take it into a tractor shop or mechanic shop and see if thet can run it down with a much bigger compressor?

Thanks for any direction on this.

Difficult or impossible to diagnose from available information.

Photos of both new and old bolts, blades and assembly might help.

Are new blades same thickness as old blades?

 

[texican]

Difficult or impossible to diagnose from available information.

Photos of both new and old bolts, blades and assembly might help.

Are new blades same thickness as old blades?

Thanks. Youre right. Let me get some pics and measurements and Ill update.

 

[Russell King]

I am not sure you really have a problem IF the bolts and the blades are from the original manufacturer (or match the original).

This is a picture of a typical blade bolt. More information is below the picture.

The bolt should have a medium shoulder diameter that fits the hole in the blade carrier (Shown in blue above). The blade carrier thickness should match the medium shoulder length approximately but I recall the shoulder length will be a little shorter than the blade carrier. Then another larger shoulder (shown in red) on the bolt should fit the hole in the blade but not as tightly as the shoulder in the blade carrier. Again the blade thickness and shoulder length will be approximately the same length. Then the threads for the nut are the smallest diameter. There is usually a washer involved between the nut and blade. The nut tightens onto the white shoulder of the bolt but does NOT put compression on the blade. The blade is free to rotate 360 degrees on the blade bolt!

The blade is installed onto the bolt, the bolt and blade are then installed (from below) through the blade carrier and then the washer is installed and nut started. Notice that there is some method on the blade bolt that stops any rotation of the bolt (green tab in above example). That tab must be aligned with the slot in the blade carrier. Then the nut is tightened to a specific torque value. The tension of the bolt is not against the large shoulder (yellow shoulder above), but the tension is from the white shoulder to the bottom of the nut. The blade is not compressed at all and should be free to rotate 360 degrees.

Since you are working beneath the shredder, that can trap and crush you, you must use some wooden cribbing to support the shredder! Do not rely on the tractor hydraulic system to hold it up. Then the blade is also pretty heavy so you may need a helper to install the washer and nut from above- but they should be careful not to push on the shredder. I used some blocks to hold it up and then installed the washer and nut but a helper is much better.

 

[Old Machinist]

Sounds like the new bolts are incorrect thread or you cross threaded them.

 

[jimh406]

I would try to find a manual for a brush cutter from Rhino or email/call them for help.

I don't use my brush cutter very much, so I've never changed/tightened blades on it. On my pull behind Swisher, it's possible to tighten the bolts too much. Going from memory, but I think it was tighten and then back off some amount (maybe 1/2 turn) or something like that. If they are too tight, they won't turn.

 

[texican]

I am not sure you really have a problem IF the bolts and the blades are from the original manufacturer (or match the original).

This is a picture of a typical blade bolt. More information is below the picture.
View attachment 167004


The bolt should have a medium shoulder diameter that fits the hole in the blade carrier (Shown in blue above). The blade carrier thickness should match the medium shoulder length approximately but I recall the shoulder length will be a little shorter than the blade carrier. Then another larger shoulder (shown in red) on the bolt should fit the hole in the blade but not as tightly as the shoulder in the blade carrier. Again the blade thickness and shoulder length will be approximately the same length. Then the threads for the nut are the smallest diameter. There is usually a washer involved between the nut and blade. The nut tightens onto the white shoulder of the bolt but does NOT put compression on the blade. The blade is free to rotate 360 degrees on the blade bolt!

The blade is installed onto the bolt, the bolt and blade are then installed (from below) through the blade carrier and then the washer is installed and nut started. Notice that there is some method on the blade bolt that stops any rotation of the bolt (green tab in above example). That tab must be aligned with the slot in the blade carrier. Then the nut is tightened to a specific torque value. The tension of the bolt is not against the large shoulder (yellow shoulder above), but the tension is from the white shoulder to the bottom of the nut. The blade is not compressed at all and should be free to rotate 360 degrees.

Since you are working beneath the shredder, that can trap and crush you, you must use some wooden cribbing to support the shredder! Do not rely on the tractor hydraulic system to hold it up. Then the blade is also pretty heavy so you may need a helper to install the washer and nut from above- but they should be careful not to push on the shredder. I used some blocks to hold it up and then installed the washer and nut but a helper is much better.

 

[texican]

Sounds like the new bolts are incorrect thread or you cross threaded them.

def not crossed..threaded them on like butter for a good ways by hand...made sure of that. YOu may be right about bolts..well find out when I get some data on my end. thanks for reply.

 

[texican]

This information is GOLD!! thanks for taking the time time withe the pics and the colors codes!!

ive read it three times...printing it out now to take home and read again and going to look for my old bolts and pull the tape on them. thanks a million for sharing you time on this...

 

[texican]

I would try to find a manual for a brush cutter from Rhino or email/call them for help.

I don't use my brush cutter very much, so I've never changed/tightened blades on it. On my pull behind Swisher, it's possible to tighten the bolts too much. Going from memory, but I think it was tighten and then back off some amount (maybe 1/2 turn) or something like that. If they are too tight, they won't turn.

its hard for me to say I tightened them too much on the first time with old nuts but buddy..they were not moving..so I guess I did but it may be due to the wrong bolt...gotta drive an hour to where to I keep my tractor and get the data on them.

 

[Russell King]

One other comment on the bolts and the am of torque = it is a whole bunch of Foot-pounds!

I used a 4x torque multiplier and it still kinda hurt my skinny arms to reach the required torque! There was not a lot of turning movement after it was tightened up by a 18 inch ratchet to reach the final torque.