Bush Hog blades hitting deck

[kthompson]

First I would do is track down the manufacturer recommended blades. On rough cut I have not known anyone who uses a blade with lift in it. That really sounds like a light (compared to true rough cut blade) weight after market blade especially if it is the one you can get to flex by hand.

I am assuming the blades bolt directly to the stump jump pan so must be bolted on the bottom. I have seen rough cut there is a bar across the stump jumper the blades bolt to and it would be possible to bolt the blades on the top of those bars which would not give the blades the clearance needed.

As to how common hitting rocks are blessed rocks are not normal here but depending on their size would say not good. A broken blade, heavy piece of wood can travel a lot farther than many realize and do damage even then. Know of a heavy piece of wood traveling at least 60 feet and hitting a car door hard enough to cause a large dent. Have known of broken blade to fly across a house.

If you have the proper blades and they hit then somewhere something was changed such as the gear box, stump jumper to affect the clearance of the blades.

Oh, verify if there is suppose to be a spacer to lower the blades on the bolts. Very possible to give easier rotation of the blades in case of hitting something solid and they have been loss over time. kt

 

[LD1]

I dont have any numbers or measurments handy, but I am pretty sure that all of the bushhogs I have owned had the blades ALOT more than 3" from the deck at rest.

Heck, an average stump jumper pan is at atleast 3" in depth. Then there is the 1/2" or so clearance between it and the deck. Then throw in the 2-2.5" offset in the mower blade and we are about 6" from the deck. And I have never seen a high lift bushhog blade that had more than ~1-1.5" wing. So without measuring....I'd say all my mowers have at least 4.5-5" of clearance with a high lift blade. And those mowers to include my woods DS96, Bushhog 105 and 306, And international IM600, and a standard duty KK5'.

Perhaps you could share some pictures of this mower, the blades, and a good shot of the underside showing the deck, blades and stump jumper / blade carrier?

 

[jb1390]

Measure your exact clearance between. The blades and deck.

3" don't sound like it's anywhere close to enough. The cutter is probably not built for....or spec'd to run lift blades.

If they are a common size, you night be able to find some lift blades with more offset.

I will measure later today. You very well may be correct - that the cutter was not designed correctly for lift blades. The sides are fairly low compared to many cutters I've seen - finding blades with more offset might cause the blades to rotate below the sides, which would not be a safe way to go IMO.

I thought about moving the gearbox and extending the sides as a solution, but that seems like a lot more effort and money than adding some 1/4" Hardox wear plate or even mild steel to the bottom.

 

[jb1390]

Reinforcing the deck by welding plate on the underside could conceivably make the problem worse, since it would reduce clearance. Like LD1, I suspect the unit isn't intended to be used with the hi-lift blades.

Agreed, adding material will reduce clearance, and if not done properly could cause further issues. Though I am thinking 1/4" material, and planning on using high strength material that is designed for impact and wear - so a hit from the blade wouldn't cause damage like it is now.

 

[jb1390]

First I would do is track down the manufacturer recommended blades. On rough cut I have not known anyone who uses a blade with lift in it. That really sounds like a light (compared to true rough cut blade) weight after market blade especially if it is the one you can get to flex by hand.

I am assuming the blades bolt directly to the stump jump pan so must be bolted on the bottom. I have seen rough cut there is a bar across the stump jumper the blades bolt to and it would be possible to bolt the blades on the top of those bars which would not give the blades the clearance needed.

As to how common hitting rocks are blessed rocks are not normal here but depending on their size would say not good. A broken blade, heavy piece of wood can travel a lot farther than many realize and do damage even then. Know of a heavy piece of wood traveling at least 60 feet and hitting a car door hard enough to cause a large dent. Have known of broken blade to fly across a house.

If you have the proper blades and they hit then somewhere something was changed such as the gear box, stump jumper to affect the clearance of the blades.

Oh, verify if there is suppose to be a spacer to lower the blades on the bolts. Very possible to give easier rotation of the blades in case of hitting something solid and they have been loss over time. kt

The blades bolt directly to the bottom of the stump jumper pan. I do not think there should be a spacer, since the bolts have a keyway that aligns with the stump jumper to prevent rotation while tightening the bolts.

The high lift blades I believe are land pride blades, and are a standard 1/2" by 3" blade, with a nice flare in it to help stand the grass up.

I agree that high lift blades do not seem to be particularly common - though I also read of many people who have trouble getting grass to cut well when laid down by tires. The cut was amazing, even in areas that were laid down by rain, and in the tire tracks.

I also would like to reduce the number of rocks in that field - but in Connecticut, I'm going to hit many more rocks unless I quit using the mower. Just comes with the territory. It seems that worn out blades or worn out bolts are the most common causes for a blade coming off - and I inspect them regularly - I understand the energy involved and the potential consequences of a failure.

 

[jb1390]

I dont have any numbers or measurments handy, but I am pretty sure that all of the bushhogs I have owned had the blades ALOT more than 3" from the deck at rest.

Heck, an average stump jumper pan is at atleast 3" in depth. Then there is the 1/2" or so clearance between it and the deck. Then throw in the 2-2.5" offset in the mower blade and we are about 6" from the deck. And I have never seen a high lift bushhog blade that had more than ~1-1.5" wing. So without measuring....I'd say all my mowers have at least 4.5-5" of clearance with a high lift blade. And those mowers to include my woods DS96, Bushhog 105 and 306, And international IM600, and a standard duty KK5'.

Perhaps you could share some pictures of this mower, the blades, and a good shot of the underside showing the deck, blades and stump jumper / blade carrier?

Yes I think pictures would be helpful. The 3" is an estimate from memory - I'll pull out the camera and tape measure when I have a chance.

 

[Notforhire]

Agreed, adding material will reduce clearance, and if not done properly could cause further issues. Though I am thinking 1/4" material, and planning on using high strength material that is designed for impact and wear - so a hit from the blade wouldn't cause damage like it is now.

Twenty years ago I knew of a rental business that had a BH 285. Being a rental unit, it got a lot of rough use. On the underside of the deck they had welded a ring about four feet in diameter, made from (I think) 5/8 X 1 steel stock. This limited the blade deflection and prevented the blades from hitting and slicing through the deck.

That said, I can't imagine that an arrangement like that would be necessary under normal use.

 

[jb1390]

Here are a couple pictures of the underside of the deck. The blades are actually only 2.5" from touching. I was checking out the brand new Landpride mowers at a local dealership the other day, comparing the design to mine. I asked for some pricing on them - seems to be around 2500 plus tax for an equivalent (but better built) mower. The blades on the new one seemed to have about the same amount of slop as mine, which indicates that nothing is worn out on my mower. There was, however, a tremendous difference in the clearance of the blades - for a couple reasons. One, it had much higher sides to begin with, and the stump jumper is installed a little lower. The other is that they install the subframe underneath the deck, instead of above it. The sales guy told me that many manufacturers are moving that way, because if a blade hits a rounded rock, it gets pushed right up into the deck if it's too close. If the subframe is underneath, the thicker steel works to protect the deck. He told me this without me talking about any of my issues - but it sounds like exactly what's going on with my mower.

I also got some pricing on steel to reinforce mine - it would be around 220 for 1/4" mild steel, and around 450 for 1/4" hardox 450 for a 4x8 sheet sheared into 16" strips. I'm not sure yet which material I'd prefer, but I'm inclined to just reinforce the deck of mine anywhere the blades touch, and buy a better cutter in a few years.

 

[LD1]

I believe the single biggest reason for the push to go with the supports on the underside is ease of cleaning off the top of the deck.

As to your situation....yea thats too close with them high-lifts. You might be able to source some generic blades that are the correct length and have a little more offset?

 

[Gary Fowler]

For a lot less money, I would take those blades to a machine shop and have them bend them to give more offset in the blades. Cold bending should not affect the tempering although I doubt that hot bending in the existing bends would hurt the tempering either. It would take 2 bends per blade to do it right and keep the cutting edge level.
Of course this option would only be used if you cant find replacement blades with enough offset in them.