# Disc mower knives hitting bar



## fxrupr (Jun 30, 2009)

I wonder if anyone else has had this problem? When I bolted the turtles back on my NH 617 disc mower I noticed that most of the knives were hitting the bar as they went around. On further inspection I noticed that even with new nuts and bolts the knives were angled down more than I think they should have been. 
I tried finding a shim washer to take the clearance out of the joint but that didn't solve the problem either. 
I finally removed all the turtles and laid them on their backs and using a straight edge measured the distance from the bench to the bottom of the straight edge on each end and at the center hole. The distance varied between 2-1/8th and 2-7/16ths, and was consistently lower on one side than the other. In addition the slots that the nuts seat into varied in angle from perfectly horizontal on one side of one turtle to down more than 5 degrees on several. Doing the math, an angle of 5 degrees over the length of the knife will make a difference of about 3/8 of an inch. If you add that to the wear in the joint it explains why the knives hit the bar. 
I wondered if this was just a wear issue but I checked a new turtle with the paint and decal still on it and it was the same. While I doubt that NH designers intended for the knives to hit the bar at any point I bet that they have the parts subbed out and they aren't checking that the turtles are being supplied to them to spec or they are checking and don't notice the problem.
I talked to my Brother who is running a New Idea MoCo and he says his knives all hit when they first start up. His solution is to cut the end of the offending knife off until it gets short enough to not hit. 
I was wondering if anyone else has come up with a solution to disc mower knives hitting the bar or stone guards? Surely the manufacturer didn't intend for them to hit. 
John


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## okhillbilly (Jun 18, 2009)

My 617 does not ever hit the bar. I've replaced all the blades due to wear or damage and the new ones have never hit. The blades are NH brand. Could you have aftermarket blades for a different model or brand ?

I noticed in another post you mentioned rebuilding it. Is there a shim or spacer missing raising the mounting hub up?


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## hayray (Feb 23, 2009)

The only problem I had that happen was on my 1409 and it was at the left hand turtle were the module bolts had lossened and caused the module to bend upward - obviously not torqued correctly at the factory. I assume that you made sure the shoulder on the knife bolt is pushed up into the resess of the turtle?


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## haybaler101 (Nov 30, 2008)

My 1431 disc mower will hit until RPM's are up. I have trashed out two bottom rollers because of loose bolts between the segments or modules. The first one NH replaced, bolts not torqued from factory. The second will be mine, didn't get bolts tight enough after replacing a shaft between modules. Bolts must be retorqued after a few hours of operation. If modules become loose, cutterbar will flex enough to hit roller.


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## Hayguy (Jun 4, 2008)

It sounds to me like your guards need to be bent down a little. If the knives are actually hitting the gear case , some shims or washers under the turtles should give more clearance.


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## hayray (Feb 23, 2009)

Seems this may be a common problem with New Holland not assembling their cutterbars correctly. I put my module back on after inspecting it to make sure the shaft was not bent. The New Holland dealer told me to how to torque it and he said that after you get the bolts as tight as you can then turn another 3/4 turn, if that makes sense. He said otherwise they will come loose.


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## swmnhay (Jun 13, 2008)

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Sounds to me like faulty manufacturing.No way should it be off 5deg or 5/16",Are the bolt holes a weldement in the turtle?I would say they were not in the jig correctly when welded.I think running it that way will cause bigger problems later.It could knock out a bearing or gearbox.I think you may need to go higher up the ladder maybe they are not even aware of a problem?

Someone else had the same problem at NAT awile back.So you are not alone.

Bottom line there is no way I would run it that way.Who gets to pay for any other repairs that this may cause.


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## haybaler101 (Nov 30, 2008)

I don't know what the recommended torque is on the cutterbar bolts, but the last time I had it apart, I buffed all the threads clean and then used a six-foot cheater bar to tighten the bolts. Ran the mower for about 10 hours and retightened again with the six-foot bar.


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## jshunter80 (Nov 1, 2009)

Hey all, I am new to the site. I thought this would be a perfect time for my first post since I have had this problem with my disc mower. I have a NH463, when I bought this disc mower I noticed after getting it home that the end disc's blades were bent up. I replaced the blades and they hit the cutter bar. I then used a washer as a shim until I could figure out what was going on. After checking it over a few times, I seen the bottom welded rings were worn which allowed the blades to tilt ever so slight. But enough that it would hit the bar. I talked to a few people about it and they said the only fix was replacing the top hat. Don't know if that helps or not, let me know.

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John Deere 5203, NH463, 894A John Deere Rake, 268 NH Baler


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## fxrupr (Jun 30, 2009)

Thanks for all the replies. My first basket case mower was a NH 462 which due to economics is now for sale as parts. JSHUNTER80 I think your 463 uses the same turtles as my 462. I will look and see if any of mine would be worth sending to you. 
According to the NH service manual for the NH 617, they say to torque the module tie bolts to 50 lbs first and then go another complete revolution. I used a 5 foot cheater on a ¾ drive breaker bar and a 1- 1/8" open end box on the other. I also replaced 2 of the spacers between the modules with used ones I got out of Cooks Salvage in Missouri. When the tie bolts get loose and you run it that way the alignment pins work in the holes in the module and auger them out making alignment impossible. What I did was take the old ¾ tie bolts and clean the threads up and paint them. The old nuts were so loose and corroded on the old bolts due to rust that I bought a box of new grade 8 nuts and washers at the bolt dealer. Less than half the price that the dealer gets. The long bolts under the gearbox I had to replace with new from NH because they were rusted 1/3 the way thru in places.

For the knife-hitting problem, what I am going to try is making ½ inch aluminum shim washers to go under each turtle like wheel spacers. Luckily the NH 617 turtle mounts on a simple round hub with four ½ inch bolts. My brothers New Idea mower has a square hole in the turtle which will take more doing. I found a guy who has a small foundry who will make sand castings for the blanks. I will then have to clean them up on the lathe. If they work out I'll let you know. I called NH corp. service and they referred me to my local NH dealer who knows less than I do about this. I think they have a quality control issue with the heat treat or stamping of the turtles. 
When I called Messicks in Pa. The service guy there told me to take a big wrench and bend the knife up so it wouldn't hit. OK that is a one-time fix but what about the new turtle I have which is just as cockeyed as the older ones? Is this one reason why we have a declining American manufacturing economy? I digress.

So before the ½ inch shim idea surfaced, to fix my problem, what I did was weld 18 inches of 1 inch pipe to 2 old knife nuts and bolt them into the 2 sockets on each turtle. I had the turtles back off the mower and this was outside on a welding bench. Then one side at a time I heated the steel around the socket with the gas ax, staying away about an inch from the welded in socket. When I had it dark red all around the socket, I applied pressure to the 2 pipe levers welded to the 2 nuts and tweaked each side back flat, first one side then the other. According to the Messicks tech guy the turtles aren't tempered but I'll bet against that. When I originally tried to flatten one out in the press I had it up to about 10 tons on cold steel and the turtle flattened out but as I let the pressure off it went right back where it had been. It's high strength tempered steel all right. Heating it dull red like I did shouldn't hurt the temper that much. You have to heat it bright red -orange and hold it there to draw the temper out.

When I was working for Trinity Industries before the layoffs, they had a problem with some 1-1/2" thick by 2 foot by 8 foot long bird backs that carried the 50 ton weight of each end of the railcar to the truck. The plant would stamp the red hot blanks and then chuck them on the shop floor to cool. You could watch the steel moving around as the wind hit it and it cooled faster on one side or the other. There wasn't one piece out of 20 made the day I was there that came close to fitting the template we had made to gage it. The assembly plant ended up using a huge press to force the cold pieces down into the welding gig. And the cars came out different shapes. Go figure. They blamed the welders and the engineers. Needless to say QC was not working well on that job.

We're supposed to pour metal Tuesday so maybe I can get the shim parts finished by Wednesday and put together by Thursday. I wonder if NH QC reads this blog?

Who better than the people fixing these things in the field to let the factory know when there is a problem? Are they listening? 
Any other brands out there where the knives hit? Any other remedies besides shims or heating the turtles or bending the knives? What I was thinking was how much longer the knives sharp edges would stay usable if they didn't try and cut steel every time they went around!

My next machine will have shock hubs on it so my drive train won't get torn up from hitting something big. 
John

2001 Kubota B7500 HST 4x4 bucket loader (actually bought new but I've had to rebuild the front axle gearboxes twice because they are not designed for actual work with a front end loader), rebuilt gray market 1982 Komatsu D20PL-6A Dozer, rebuilt 1967 MF 1100 tractor, rebuilt 1961 MF 35, rebuilt NH 617 mower, rebuilt 14' Kewanee offset disk harrow, home made 2 axle 4 yard dump trailer, rebuilt 3 axle 20 foot dovetail gooseneck trailer with rebuilt Warn 20 ton winch, rebuilt 1982 1 ton Chevy pickup to pull rebuilt gooseneck and homemade dump trailer. There are no payments. We own all our junk outright.


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## hayray (Feb 23, 2009)

What are the bottom welded rings you guys are talking about?


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## fxrupr (Jun 30, 2009)

hayray said:


> What are the bottom welded rings you guys are talking about?


I think JSHUNTER80 was talking about the forged fittings which are welded into the turtles for the knife holder nuts to attach to. I noticed on a couple of really worn ones that the underside of the socket fitting gets worn by the knife enough for the knife to hang way down. But I also noticed that with a brand new nut and bolt in a new turtle that the blade isn't held out at 90 degrees but has enough clearance to droop a quarter of an inch. If your turtle has also got a droop to it .....clackity clack.
John


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