Retaining mower blade bolts...

[SteveH-CO]

I maintain/manage our church lawn equipment. We have a typical Troy Bilt riding mower with 2 blades. In spite of our best efforts, the blades work loose and have fallen off a few times. We try to torque them to spec (90 lb-ft or so), but people (volunteers) hit things and loosen the blades, and I can't be there to inspect them frequently. Torquing them is very awkward, of course.

What sort of liquid thread locker (or other technology) should I use on the blade bolts? It can't be permanent, but should resist vibration, etc. I typically use thread locker on much smaller fasteners, and I don't want to use the wrong stuff and the have to heat it with a torch to remove it. Suggestions? Another approach?

Thanks - Steve

 

[Ole Slewfoot]

You have damaged or wrong parts. I hit things with the blades of my rough mower till they lose 3-4 inches, and they dont come loose.

 

[kd3pc]

most blade bolts will have a cupped washer to keep this from happening...you might check the manual or with the dealer...this should not be happening and could hurt someone.

best of luck

 

[JJThrasher]

I just use a half inch impact to install and remove. Never had one come loose and it won't without an impact or the hulk reffing on it.

 

[mailpup]

You can use blue Locktite which will allow disassembly without heating. However, consider replacing your bolts. They may have been over torqued at some point and if they are stretched, they won't stay tight. If you don't already have them, I would use lock washers also.

 

[dadsEH]

Newblades.....NEW BOLTS!

 

[chruler]

If the holes in the blades become elongated, they will be more prone to coming loose.

 

[LXCam]

If all else fails get some Nord-Lock washers from mcmaster.

 

[SteveH-CO]

All good suggestions - thanks.

Indeed, there may be cup-shaped washers that are missing - those would be the first thing lost when the bolt comes loose. I will read the owners manual and see what hardware is actually supposed to be installed on there. Failing that, perhaps blue Loctite.

 

[APEowner]

I agree that there's something else going on besides loose bolts. I'm thinking either missing hardware or just the wrong blades for the application.

 

[sberry]

Oil the bolts with common spray and rattle on with an impact gun. Some do use cup washers and some hardened flats and never seen one with a lock. I really doubt someone been over tightening these and stretching bolts, likely they never been tight enough.

 

[jimgood]

Yeah, that's weird. I've never had my blade bolts do anything but get tighter.

 

[countryroad82]

I have a mower on my fleet that for some odd reason the outer blade loosens over time. I replaced the bolt didn't work, replaced the spindle still dropped the blade, I laid the red Loctite to it no problems. It helps though that I use an impact to remove the blades though. Every time I put new blades on, just that one outer spindle gets Loctited and no issues. Before I get flamed for red, I tried all the other colors before red. Red worked. But the mower in question is an Exmark Lazer ZXS with I think a 25hp engine........ It's got a little umph to it lol.

 

[SteveH-CO]

Countryroad82 - I have seen cases where you had to move up 1 grade of Loctite to get the response you needed.

If this were my personal mower, I could watch it more closely, but since several people use it, you never know what sort of abuse/craziness goes on that may be affecting the blades. Can't help that - it's how volunteer situations work.

 

[justme-]

Something is wrong, blade bolts shouldn't loosen. I'm a tech and have never had that as a complaint. In fact unless damaged there's no reason to change blade bolts with a new set of blades either.
I've serviced mowers on their 3rd or 4th set of blades and the original bolts and mounts. Some from impact damage and others from life.
Don't oil them, grease them, anything them.
Blade bolt should have some sort of lock washer. Some manufacturers use cup washers, others regular split lock washers.
Odds are there is a missing lock washer and insufficient torque. Walk behind mowers get 200inlbs max (because that's what my cordless impact does) or about the best I can do with a long handle 3/8 ratchet
Honda mowers should be hand tighten only or they will strip.
Riders get the air impact, ir231 on setting 2-3.

 

[sberry]

Mine has had a dozen sets of blades. Each set has been R&R 4 or 5 times. That would make the bolts been in and out 60 times or so. Every bolt should be oiled.

 

[pepi]

Is the blade mounted with a bolt or a nut on the end of shaft? Either way there should be a lock washer sandwiched in-between the blade and the nut or head of the bolt and the blade.

 

[JPinSTL]

The 6ft belly deck on my Kubota does the same thing. Not all the time either. I've had it since new, no missing hardware, etc. The last few times I've just been giving that spindle an extra burp from the rattle gun. It uses 2 stacked cup washers. I'm thinking I may need new washers.