Rotary Cutter Bush Hog 296. Blade holder keeps coming loose.

[Larold]

I bought a used bush hog 296 which works great except for the blade holder coming loose. The bolt has a key in it so Its probably not the bolt. I cut 40 acres with no problems but when i got it back to the shop for maintanence i noticed the blade holder had some play from side to side. The bolt was extremely tight so 200.00 worth of tools later i was able to get the blade holder tight again but the bolt was 1/4 " further up the shaft so i had to put 2 washers in to make up for the gap. I tightened the bolt with a 3/4 inch impact rated at 1000 lbs torque and installed the key. Now after only 15 acres its coming loose again.

 

[Larold]

http://www.bushhog.com/images/stories/documents/manuals/290seriesparts.pdf
I had to add 2 of the washers listed as part 8 in the diagram.

 

[Larold]

On page 4

 

[Gary Fowler]

So the whole stump jumper is loosening up from the splines on the gear box. My bushhog shaft is tapered a bit, so it could be that yours is worn some and by tightening it, your are just working its way up the shaft till it gets tight. If it has been used a lot with it very loose, it could have damaged the splines on either the gear box or the part that fits on to the stump jumper and blades. I think I would remove it from the gear box and examine it closely. I find that it is much easier to work on a bushhog (assuming you have a FEL) if you just stand it up on its side and keep it stabilized with the FEL

 

[Larold]

Thats what I was afraid of. I just have 50 acres left so im hoping i can limp it thru and then ill have plenty of time to order the parts. Crossing fingers its the blade holder that's wearing out.

 

[Larold]

Im wondering how it got loose in the first place so when i put the new parts on it doesn't do it again.

 

[Larold]

Well, I tightened it back down as tight as my 3/4 inch impact could get it, stuck in the cotter key and cut 30 acres. Its still as tight as it can get so looks like I dodged a bullet. Ill check it constantly just to be sure. Thx for the response. Has anyone else had one come loose? I haven't hit anything with it and I run it just under the recommended RPM.

 

[SPYDERLK]

It got loose because it wore from not being tightened correctly and wearing by moving over time. The stump jumper jams pretty tite on the taper spline. Its hard to get off after a proper tightening and maybe somebody chose on the loose side. Now you have wear. If it wears loose again maybe replacing the stumpjumper side of the joint will be enuf.
larry

 

[jeff9366]

This may be helpful....or it may not.

Swedish Nord-Lock washers really secure nuts. They are a staple in the aero-space industry. I use them under the nuts on my Howse Disc Harrow and no nut has come loose, torqued only with a wrench.

Fastenal sells Nord-Locks. However I buy them on eBay for convenience and selection.

Nord-Lock items in Page Auto Supply store on eBay!

 

[SPYDERLK]

Not letting the nut back off is one thing. Regardless, if the joint moves wear will cause it to loosen. High cyclic loads will cause faster wear and quicker "loosening". The key is tight enuf to eliminate movement.
larry