Nh460 moco question.

So what grade bolt should I use between the wobble box and the sickle bar?? I have snapped 3 or 4 bolts today. I have tried grade 5 and they last for a little while but I have broken 3 of them. Hay is super thick and also as some debrea from the floods we have had. Lot of old dead grass etc in it but have to get this cut and baled since there is also a whole lot of good hay in it. Seems this year I can not win for loosing. This is the 2nd machine that is having problems cutting the hay this year. I plan to try grade 8 bolts but not sure if that is a good idea of not or if maybe that is what I should be using in the first place.
Thanks

Are the guards and sections sharp? Rounded guard/ledger edges do not cut grass easily.

Book says grade 5.

Is the knifehead bushing in pretty good shape ? I am pretty sure any worn parts that could cause a shock load on the bolt would be bad news for the bolt.

Our local independent repair shop told me to use Grade 8 fine thread bolt on a 461. They are not meant to be a shear pin as I understand it. I have had the same bolt in there for the past few years but I keep a spare. When I first got the haybine it would shear 1-2 a year and wear out a bushing every year, but once I got the knife back straightened out better they last a long time.
Zach

Bushing if in good shape. Every thing is nice and tight just this hay is super thick and tough due to all the rain and floods and dust etc. Sections are also all in good shape and sharp

Yep guard and sections are all in good shape and sharp. Hay has a lot of dust and is super thick due to lot a of rain and now it is very hot and getting real dry

Make sure the thing is in mid stroke when you tighten the bolt.

Either the blade is getting in a real bind or its not as sharp as you think it is.I'd try
cutting a littler higher.

As a turnabout, I may actually have some experience that would help you for a change.

Watching my older brother tune the haybine as a teenager, I learned a few things:

He was fussy about the guards being in a straight line. A few times a year, or whenever he could visually see some guards out of alignment, he would straighten the offending guards back into the row using a piece of pipe that fit over the point. He scoffed at my cousins that needed come-a-longs, an ATV or even a tractor to pull the knife out of his haybine. He could pull his with one hand and little effort. I'm assuming that you have this taken care of.

He was fussy about sections. He had two extra knives in the garage at all times with all worn sections replaced (which he did on rainy days). So getting sharp sections was a ten minute procedure...pop the wobble drive bolt, pull out one knife, put in another knife, replace the wobble drive bolt.

When I started cutting for the farm that my wife and I started, it was with a friend's haybine... I followed the advice above, but I still broke a couple of bolts and ruined a few bushings. Why?

1. I learned that the nylon-insert locknut on the bolt was essentially a throwaway. I re-used the same nut a couple of times and learned not to the hard way. Now, every time that the wobble drive bolt comes off, I put a brand new nylon-insert lock nut on it. Maybe some locktite too, if it's handy.

2. Torque that sucker until you stain your underwear. I keep a two foot section of pipe in my toolbox that slides over my breaker-bar handle and I'm not afraid to use it on wobble-drive bolts.

3. Thatch is a killer. My friend's fields hadn't been mowed in a few years. The grass was dry, thin and wire-like, which cuts hard enough. It also had some thatch down below the undergrowth. His mower had no shoes on it, which put the guards right down into that thatch. Even with sharp sections, good straight guards, a new bolt, a new bushing, a new nut and enough torque to require bleached underwear....something is going to give if the mower is down in that thatch. That's when I learned how to replace the wobble drive's drive belt.

4. I use grade 8...just because I hope that they would break more cleanly if they did break.

5. The most important lesson after all of the above is...I learned read my friend's fields and recognize these thatched areas with wiry grass. In those areas I learned to feather the hydraulic controls on the tractor to keep the guards up out of that crap and save myself some bolts, nuts, bushings and belts.

On all the N.H. hay bines I've had, the book called for 85 ft. lbs torque on that bolt. I never had any problems when I used a torque wrench on them. I did just use a breaker bar on a 477 and it came loose & broke the bolt in about 3 days. Pretty much made a believer out of this old man. LOL

Ya I did notice yesterday when I had it set a bit lower was when the bolt would break. Hard to get it where you want it each and every time. Sections are still real good if has only cut maybe 40 acres since they where new. But with this hay having all that trash from the floods and the hay being super thick it does seem to cut a lot harder plus all the dust on it

(quoted from post at 09:02:32 07/31/15) On all the N.H. hay bines I've had, the book called for 85 ft. lbs torque on that bolt. I never had any problems when I used a torque wrench on them. I did just use a breaker bar on a 477 and it came loose & broke the bolt in about 3 days. Pretty much made a believer out of this old man. LOL

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I wouldn't argue with you on that.

Even though I have been tightening mine probably more than 85 ft.lb, I think that there must be a point where there's too much torque and I would just be making things too tight to move well and pre-stressing the bolt.

I think that, of the changes that I personally made, using a new nut/locktight every time that I remove that bolt is probably more important to keep things from loosening up than the borderline overtorque that I put on the bolt.

I also wanted to add that, I've more recently used my own Hesston 1070 that I just got, so I've "graduated" from my friend's NH 467.

The Hesston came with stub guards on it. I haven't tuned it/mowed with it enough to see if I'm satisfied with the quality of cut from the stub guards (the reel needs adjustment badly), but I did mow through a lot of areas that would have plugged the 467 or at least strained the wobble drive because of thatch and tangled vegetation. The stub guards appear to take less effort to drive the knife through and plug less....

To old...if you have a couple of mowers having issues...maybe try stub guards on one and see if it has less trouble in these trashy areas that are causing so much stress on the wobble drive????

If you're breaking knife-head bolts, it is an indication that your knife-head bushing is going bad. When you pick up the bushing at the NH dealer, just get a bolt there. That bushing just goes bad about every 300 acres. I always carry an extra bushing and bolt in the haybine tractor's toolbox. If you break the knife-head bolt and the area is hot to the touch, the bushing is shot.

The bushing that is in it has only cu maybe 50 acres if even that much since new. I keep one on hand since I know they got bad but they have to be pressed in so that is a real pain in the back sides