Mowing Stump Jumper question...

Eastbx · Jan 30, 2011

I've been rebuilding what I think is a very old and beat up 5' Howse brush cutter. I replaced seal on input shaft, had the steel casing rebuilt and purchased a new blade pan. Now I purchased the $45 blade bolts, recommended by the sale rep, from the same place so I assumed they would smoothly fit the blade pan but they didn't. The bolts have a squared key while the pan has a rounded key slot. I'm not sure this is the first time I had to assemble a cutter but when I explained to the sales rep about the lack of easy fit, he explained the bolts had to be POUNDED into place, then tighten to some 300lbs torque.

I'm not sure but square key into round key slot just doesn't sound right? Can anyone advise or confirm "The Pounding".

SandburRanch · Jan 30, 2011

Eastbx said:
I've been rebuilding what I think is a very old and beat up 5' Howse brush cutter. I replaced seal on input shaft, had the steel casing rebuilt and purchased a new blade pan. Now I purchased the $45 blade bolts, recommended by the sale rep, from the same place so I assumed they would smoothly fit the blade pan but they didn't. The bolts have a squared key while the pan has a rounded key slot. I'm not sure this is the first time I had to assemble a cutter but when I explained to the sales rep about the lack of easy fit, he explained the bolts had to be POUNDED into place, then tighten to some 300lbs torque. I'm not sure but square key into round key slot just doesn't sound right? Can anyone advise or confirm "The Pounding".

-------------------------------------------------------------------
Try checking the hardness of one the bolt keys with a file. If a file won't touch it like it's hard as the hubs of **** they may have designed it to act as a broach as it enters the rounded key way.

wood butcher · Jan 30, 2011

That doesnt sound right.

whistlepig · Jan 30, 2011

Eastbx said:
I've been rebuilding what I think is a very old and beat up 5' Howse brush cutter. I replaced seal on input shaft, had the steel casing rebuilt and purchased a new blade pan. Now I purchased the $45 blade bolts, recommended by the sale rep, from the same place so I assumed they would smoothly fit the blade pan but they didn't. The bolts have a squared key while the pan has a rounded key slot. I'm not sure this is the first time I had to assemble a cutter but when I explained to the sales rep about the lack of easy fit, he explained the bolts had to be POUNDED into place, then tighten to some 300lbs torque. I'm not sure but square key into round key slot just doesn't sound right? Can anyone advise or confirm "The Pounding".

This looks good to me. The blade stud is swaged into the stump jumper. A very tight press fit between the shoulder and key is important. You want the blade wallowing around the stud and not the stud wallowing around inside your stump jumper. I don't pound these in. I take my super duper impact wrench and let it do the work.

TO_Bud · Feb 1, 2011

From the looks of your photo of the keyway slot there is a rounded portion but the sides of the slot are straight. If the fit between the key and the straight sides is nice and tight the rounded portion becomes irrelevant. That's if the key has clearance to fit snugly into the round area as well and doesn't slip out of the bolt slot. As Whistlepig states just hammer it (or pull it) flush with the bolt shoulder and you should be good to go.

Eastbx · Feb 1, 2011

Thanks Gentlemen, It just didn't seem right at first... I'll just slam that puppy in there and be done with it.
Appreciate the help!!

gpick · Feb 4, 2011

I think the main (if not only) purpose of the key is to keep the bolt from turning while tightening the nut through the hole in the deck. There are a variety of bolt types used for different mowers and some have no key but have a hex head on the bolt as well as the nut. Good luck installing that one by yourself. When I last changed blades on mine after 20 years, I found my blades must have been installed by the 300 lbs of torque guy. That, combined with the 20 years made the nut so tight a dozer mechanic couldn't free the nut with a super heavy impact air wrench. We had to cut the bolts off with a torch.

I replaced the blades with bolts that look just like yours except mine had a castle nut. No 300 lbs of torque necessary -- just snug as the nut cannot back off which is the only real issue. Takes a little fishing to get the cotter pin in or out, but the nut comes off easy. Easy enough I actually plan to sharpen the blades this time.

P.S. I think that salesman is the one that needs pounding into place.

Soundguy · Feb 5, 2011

if the round part of the yeyay is too shallow hit it with the side of a flat file till the key has room to enter.. then pound away. just don't make the keyway wider.. only deeper, and only if needed.

it's very likely that bolt is way harder than the pan/carrier bar..

soundguy

kjung17 · Feb 5, 2011

The square peg/round hole system allows for deformation when the bolt is torqued. Properly torqued, Not hammered til the impact wont turn anymore or mashed down with a 6 foot cheater. As stated above, the blade should move on the bolt. The bolt should not move in the disk. Over torque is every bit as dangerous as under torque. Use your torque wrench. We service commercial boom mowers requiring 850 ft/lbs on the blade bolts. A customer tried to guess at his torque and sent a blade through a womans house trailer and ruined her above ground pool, no injuries.

mojoinco · Feb 9, 2011

I usually am able to remove old nuts using a fair amount of heat on the nut and bolt (thought 300# is a lot to remove).

But wait, you have a new pan, and new bolts. All you need are the old blades. Cut/hack/grind away!