NH 718 chopper

Doug Wi · Jan 13, 2016

Need to set up the knives on my 718. Housing is moved up as far as it will go, shear bar is near the end of it's adjustment, and it doesn't blow corn silage very well. Knives are in the middle of their adjustment slot. Problem is the bolts that hold the knives are worn enough that the socket won't hold to turn them. Got a couple loose with a 3/4" breaker bar with an 18" cheater pipe on it, but most are rounded enough that socket just slips up and off. tried heating the knife holder behind the knife where the bolt screws in, but the knife started to turn red and I would think they are heat treated, so that's not good. Anybody got any suggestions on what to do next? Chopper really in pretty good shape, so hate to walk away from it, but may have to.

NY 986 · Jan 13, 2016

Can the shear bar be flipped or is it worn on both sides? Would a new shear bar help you out for the time being? I assume you are looking for the least expensive way out? It sounds like moving the knives for the time being is not a preferred way to solve the problem. If the machine is in good overall condition it might be time to look for a 718 parts donor. I tried looking for a parts diagram to tell if there is a removable nut or if the knife bolts go into the cutterhead itself.

NY 986 · Jan 13, 2016

I finally got to view a parts diagram. The knife bolt which is supposed to be grade 8 threads into the knife support. Sounds like the knife support needs to come out along with the knife to apply penetrating oil or heat directly. Sounds like a good winter time occupier and may demand a parts donor machine.

centash · Jan 13, 2016

Should be able to remove the knife support with the knife on it to access the nuts underneath. There should be a bracket (knife holder) that bolts to the cutterhead with 3 bolts on each side. With this out, you can cut the old bolts out as a last resort. Flipping the shear bar won't help it blow; you can get a paddle kit that bolts under the knife to help blow the silage. The procedure to reset the knives/shear bar has to be closely followed to get the best results and to avoid damage to the knife/cutterhead/shearbar.
Those are a pretty good little harvester, ran a super 717 and a 718 for years.
Ben

RickB · Jan 13, 2016

Can you pound a 22MM six point socket on the worn bolt heads? Heating the bolt heads cherry red will allow the bolts to stretch reducing th eclamp load and they will loosen easier. Bolts and washers are junk anyway.

NY 986 · Jan 13, 2016

There are no nuts shown in the diagram in terms of holding the bolts which attaches the knives to the mounts. A fresh shear bar or if the existing bar is good on one side might put off the job of tangling with the knives if the OP so chooses. If the bar as it sets is worn then the cut is getting ragged and taking more power via more fuel to do the job. Paddle kit would no doubt be an improvement but getting a clean cut might get things back to acceptable for the OP.

JDSNOW · Jan 13, 2016

Doug where are you in wisconsin? I am also in wisconsin. Born and raised on new holland pull types feeding 150 dairy cows. We now run two 900 harvesters. Me and my father both work on new holland harvesters on the side. Depending how close you are maybe one of us can stop by. We remove knives with six point sockets and big impact wrench. Then set your knives with the sharpening stone as a reference.

centash · Jan 13, 2016

If you set the knives out as far as they can go, you will have to drop the housing; however, from there you can tighten things up and get like new performance without the paddle kit.

Ben

Buckeye · Jan 13, 2016

I bought a six point socket and 3/4 inch heavy duty impact wrench with 1" air hose to get mine off. Use the impact wrench for a lot of other things too. Really works well on John Deere wheel bolts and disk gang bolts. A lot faster and easier than a breaker bar and cheater! Your 718 should have two guide markers on each side to adjust the blade up to. IIRC they look like square stock steel and move into the chamber.

Doug Wi · Jan 13, 2016

Thanks for the replies. The shear bar is good. jdsnow I am in the nw corner of wis half way between mpls/stpl and Duluth/ superior. I thought about taking it apart at the knife holders but didn't know if I would gain anything. Several mentioned heating. I tried that and the knife was turning red. Isn't that going to mess up the temper of the knives? I have 175psi air preasure. think the impact has 900 ftlbs in reverse. Will have move the chopper to get closer to my 1" air line. May have to get a bigger hose to feed the wrench. Thanks again for you alls time.

RickB · Jan 14, 2016

Heat the bolt head, not the knife. Hard & fast, the knife shouldn't get hot enough to turn red.

NY 986 · Jan 14, 2016

Yeah, I would try avoiding direct heat to the knife hence removing the knife with the support still attached. I would bet the juices from the forage have rusted it good. Direct heat and/or penetrating oil to the support where the bolt threads in. Right now there is plenty of time if things progress real slow.

jim_uny · Jan 17, 2016

had a nh 718 w elec controls and liked it. contactamish NH after market parts maker for catalog and discuss your problems. get a catalog. see item jm717718 thrower paddle on cutterhead. this may help. 717.464.1043

Donald Lehman · Jan 17, 2016

If all else fails, grind the heads off the bolts and then remove the knife. The bolts should come out easily with a pair of vise grips once the pressure is off the threads.

NH 718 chopper

Doug Wi

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NY 986

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NY 986

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centash

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RickB

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NY 986

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JDSNOW

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centash

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Buckeye

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Doug Wi

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RickB

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NY 986

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jim_uny

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Donald Lehman

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