Blade Bolt problem

[jekjr]

We change blades on two Tiger Cats daily. Some times more than once depending on the day and grass.........

We change them with a cordless impact and a floor Jack. On a few occasions we have had a blade that we can not remove. Impact won't break it loose. Cheater bar on a socket with a wrench fouled inside the deck on the bottom as a back up will some times get it to break. Yesterday we had to take a 1/8" blade on a 4" side grinder and cut the bolt off right at the bottom of the nut to get it out.

This was actually the second bolt we have had to do that to this year.

Have any of you had this problem? What did you do to rectify it.

 

[reynoldston]

Seeing you really don't want to use heat in that area because it would be bad for the bearing and seals. What I use is what they call a air chisel or air impact hammer. I install a very dull chisel bit and hammer on the side of the frozen nut. This will loosen the nut. It works for me but also remember you get what you pay for when buying a air impact hammer.

 

[jekjr]

Seeing you really don't want to use heat in that area because it would be bad for the bearing and seals. What I use is what they call a air chisel or air impact hammer. I install a very dull chisel bit and hammer on the side of the frozen nut. This will loosen the nut. It works for me but also remember you get what you pay for when buying a air impact hammer.

For us working in the field mostly it was more practical to just whack the bolt off and put a new one in. Those bolts are not that expensive and the cost of the bolt quickly offsets the down time. I am just curious what causes this to happen from time to time.

 

[cpurvis]

If the impact won't remove the bolt, how did you get the threaded portion out after you cut the head off?

If it comes out freely at that point, I'd say you're tightening them way too tight.

 

[reynoldston]

For us working in the field mostly it was more practical to just whack the bolt off and put a new one in. Those bolts are not that expensive and the cost of the bolt quickly offsets the down time. I am just curious what causes this to happen from time to time.

I am in the repair trade. You must be talking about the cap screw that go's through the spindle and the nut that holds the blade on style. Yes I have found some of that style very tight and hard to remove the nut. My self when that happens I use a 3/4 ratchet wrench with a long bar and have never found one that didn't come loose yet. Just how do you whack that large bolt off with? As I recall its a 5/8 or larger bolt. To me it would be easier just to split the nut or use the air chisel to loosen the nut. You have your ways and I have mine.

 

[bertsmobile1]

First, the bolt tightens due to the resistance of the blade going through the grass , the longer the grass the tighter the blade will become. I have to cut a few off each season so you are not alone.

I ended up with a 1500 ft lb air impact hammer to do this job.
Not cheap , around $ 600 Aus but worth it in time saved.
Even with this gun I still have to cut one off occasionally.
If you do this job daily then get some tools made to do the job.
A block of hardwood with a notch in one end deep enough so it can not easily fall off the blade which is the right length to brace the blade against the deck and a deep impact socket on a 4' breaker bar should do the job or better still a 6' breaker bar.

In the field van I keep a 3/4" standard socket set , a 4' breaker bar ( also 3/4" ), a few blocks of hardwood and a scissor jack.
The jack goes between the blocks of hardwood to make the distace correct to lock the blades.

A customer uses a block of hardwood with a slot cut into one end to fit the blade and a V notch on the other which slots over a spindle . This locks the blade against the adjacent spindle
To turn the nut he uses a podger ( slogging spanner ) and a very long bar, around 6' foot and that turns the nut with very little force.

 

[Mad Mackie]

Either overtightened on not tight enough.
75 FTLBs dry is the torque spec.
I understand your need for a quick blade turnaround, but this is when things can get problematic.

 

[motoman]

I am not a pro and do not handle more than one rider...But ignoring the tensile strengths of bolts and their required torque is asking for trouble. Unless you have an air hammer torque wrench with adjustable settings a la NASCAR you do not really know if you are properly stretching , or overstretching the bolts. This is further aggravated by any habit of applying anti- seize or even engine oil as a lubricant without making downward adjustment to the torque settings. A "dry" bolt as described by Mackie is the baseline torque called out in any factory manual. Spark plugs with galvanized threads are "lubricated" by the galvanize material and additional lube should lower the torque applied. Something like 70% of the torque applied is to overcome the bolt head shoulder. There is a chart in this forum with torque settings and lubricant adjustments.

 

[bertsmobile1]

I am not a pro and do not handle more than one rider...But ignoring the tensile strengths of bolts and their required torque is asking for trouble. Unless you have an air hammer torque wrench with adjustable settings a la NASCAR you do not really know if you are properly stretching , or overstretching the bolts. This is further aggravated by any habit of applying anti- seize or even engine oil as a lubricant without making downward adjustment to the torque settings. A "dry" bolt as described by Mackie is the baseline torque called out in any factory manual. Spark plugs with galvanized threads are "lubricated" by the galvanize material and additional lube should lower the torque applied. Something like 70% of the torque applied is to overcome the bolt head shoulder. There is a chart in this forum with torque settings and lubricant adjustments.

Doing up is not the problem.
It is the undoing that is giving the OP grief.
FWIW I alway use a tension wrench for blades without fail.
It is my comeback should one ever come adrift & I get sued.
Even so most of the mowers from my commercial customers that I am the only parson who normally works on them require a massive amount of force to undo the blade bolts because they self tighten during use.
They are designed to do just that which is why rear discharge decks with counler rotating blades use a Left hand thread on the left cutting blade.

 

[jekjr]

If the impact won't remove the bolt, how did you get the threaded portion out after you cut the head off? If it comes out freely at that point, I'd say you're tightening them way too tight.

On a Scag the bolt goes all the way through with a nut on top.