Reconditioning the cutter bar on my NH451

[DogT]

I posted in Attachments but got no takers. I'm replacing all the sections and double guards on this old 451. I did it before 5+ years ago. What I didn't like before was I had to take a large pipe wrench and long heavy EMT tube as an extension to bend the guards up to meet the sections. I know this is probably wrong. This time I've got new wear plates and hopefully the sections will rest correctly on the guards.

Anyone have experience rebuilding the cutter bar on the 451? I've got the sections, the guards are coming Tuesday. I probably should have gotten the double hardened German ones but I ordered the cheap ones before I saw them. Search: 3 results found for "219120*"

Are those rivet tools worth the $90? I can hammer on sections pretty fast with my 225 lb anvil and 2 lb rounding hammer. I punch the old rivets out with a Diamond horseshoer's clinch cutter after I grind off the rivet head on the section side. The narrow end.

But where the sections are sandwiched between 2 bars I usually end up drilling them out, they don't co-operate with the punch.

 

[DogT]

Well, I started putting sections back on the bar today. The bolt with the drilled out dimple did not work great, it wobbled in the anvil too much and didn't make the head of the rivet seat nicely on the bar (bottom) side. So I just went back to my old method of putting one rivet in the right way against the anvil, put the other rivet in the section upside down just to hold it in place, put my thumb over the upside down rivet and used my 2 lb rounding hammer to seat the other one in place, then turned over the upside down rivet and finished the section. It does leave a flattened area on the underside of the rivet, but that won't matter, and the top looks just flat from the hammer. They're good and tight though and looks like they swell nicely in the holes. It takes about 10 nicely placed hits to get them in right and you just can't be casual about where you're hitting the rivet or it skews to the side, so one has to be careful to hit it right.

No one has rebuilt their bar before?

 

[DogT]

Finished bar. I didn't replace the far inside and outside ones, they weren't that bad.

 

[DogT]

I got the guards today. I was looking a the current ones on the bar and it looks like only the end few are worn badly. I may just stick the sickle bar in the old guards and try it out. Otherwise it might turn into a 2 day project the way I work at my age and probably having to adjust everything again.

 

[DogT]

So I put the bar with the new sections back on the old guards. Thing cuts through the grass like a hot knife through butter. In the south field, it's not so hilly, not so many trees or rocks and I can move along in 5th gear. According to the meter that's only a bit above 3mph, but I don't believe it. I certainly couldn't keep up that speed without going into a pretty good jog. So in an hour and a half I finished about 1/2 to 2/3's of the field. I think it's about 10 acres. I could have finished but the wind came up, temps dropped and dark clouds came in so I quit before I got wet. Of course nothing happened, I could have finished the field, at least the easy parts. Left the house at 2, got back in the house at 3:30. If I could have had another 2 hours I would have finished. It's the cleanup around the trees, banks and rocks that takes time.

When I can move along in 5th gear the grass also falls back better, the divider rods separates the grass at the end of the bar better and it makes it easier to work the next row. If it doesn't rain tomorrow I should have that field done in record time.

Seems it might be worth just to put new sections on the bar every year for $50 a bar and move along mowing faster. Something I can do when the weather is cooler, not 90° and 80° humidity. But at 77 I'm not sure how much longer I can do this. I have to work sitting on used spackle buckets, it's just too hard to get on the ground and then get up. All my back and nerve problems don't help.

 

[pmsmechanic]

So I remember my Dad removing sickle sections in the vice. Loosely grip the sickles in the vice and rest the bar on the rear jaw. One good hit with the hammer on the sickle and the rivets sheered off. The sickles were located about 1/4" past the rear edge of the bar. It's a 2 person job but was a quick methid of removing all the old sickles.

 

[DogT]

That's good to know. What I've done is use a grinder on the section side to remove the rivet head and drive it through the section and the bar all at once with a punch. One time after I removed the heads, I knocked off the sections with a hammer but that left the rivet sticking above the bar and then I had to remove the left over rivet again with the grinder and then punch it out of the bar. Not a good idea. Better to knock out the rivet through both the section and bar an one whack.

Anyhow, I'm glad it's working so good. It must be the guards are not that important, the sections must have to be sharp to cut right. I may try just sharpening the other section bar I have and see how it works.

If I could move in the North field as fast as the South, it would take me half the time, but it's too hilly and too many turns/trees.

It's certainly faster than the 5' rotary mower by any count and I don't have to drive through all that grass seed blowing around.

 

[pmsmechanic]

You can also buy bolts that are especially made for sickle sections. Here is one supplier. Just google section bolts or sickle bolts. They are easier to use than rivets. The only downside is that they need to be removed completely to replace a sickle when the knife is in the bar.

cutting section bolts and rivets

qualityfarmsupply.com

 

[DogT]

I have a hard time believing that a bolt would hold the section on better than a rivet. It certainly won't fill up any voids in the holes. I'm sure they're useful though. Whether you use a bolt or rivet, one has to take the bar out to replace it.

So I finished the south field this morning, took me an hour and half including cleaning around some trees and rocks. So a total of 3 hours. I usually plan on at least 5 or 6 hours to do that field so I've cut my time in half. We'll see what I can do the North field in next time. I think it took me 6 hours last time and it was cutting good, but I had to move in 4th gear. I still need to figure how fast I'm going in what gear. I can't believe 3mph is 1500rpm in 5th gear. I can almost quick walk that fast. If it were a rectangular and flat field with no obstructions, I could probably get into 6th gear.

I've still got 2 small maybe 2 acre fields I need to finish up this spring. In the past I used to try to cut all the fields 3 times a year. Since we've gotten rid of the horses and cattle, the weeds are about non existent in the fields now, or at least not noticeable.

 

[pmsmechanic]

I have a hard time believing that a bolt would hold the section on better than a rivet. It certainly won't fill up any voids in the holes. I'm sure they're useful though. Whether you use a bolt or rivet, one has to take the bar out to replace it.

There are many swathers with bolts instead of rivets. I haven't got any experience with bolts so I can't say one way or another. I've replaced many sickle sections without removing the bar. It might not be much of a job on a 5-7' mower but as soon as you get to 14 -36' swathers it's a lot easier to replace sickle sections on the machine. Sometimes you need to remove the guard for room but it's quite easy to set a rivet on the machine.