4" Sundown brush hog, have questions

garye5007 · Aug 8, 2016

Hi,I have a Mahindra Max 25 Tractor and I picked up a 4" sundown brush hog (used) looks to be in pretty good shape. I didn't get a manual for it can't seem to find one online. I know very little about these things...
gearbox oil looks good (not milky)and it spins very freely. My questions are, 1.) is shakes.. I presume it's unbalanced. 2.)the blades attached to a stump jumper, are VERY dull. the nuts holding the blades to stump jumper are welded, is that normal? So to sharpen I figure I have to remove blade and jumper assy? How do I get this somewhat balanced when sharpening? One last thing, do I need a slip clutch? I don't have a clue what to get for bolts if I don't. Probably gonna have to hit you folks up for the adjusting everything to the tractor part in another thread.

Thanks in advance for any advice! Gary

The Deerslayer · Aug 8, 2016

If that is really a 4" (inch) brush hog, I suspect it will take you quite some time to do any brush hogging or like many of us here, you REALLY like your seat time:laughing: Seriously though, don't worry about the dullness of the blades as they are suppose to be that way. A brush hog is designed to smash more than cut. I have never sharpened mine and they have worked extremely well for years. I mainly use it for keeping the pastures down as well as on some actual brush and saplings. Mine does not have a slip clutch but has shear bolts that perform as expected. Check to see if yours has them. Some shaking can be normal, but if excessive could be an issue. Not sure if they can be "balanced" like a lawnmower blade. Check to make sure the blades are the same length and in the same condition. I imagine if one was replaced by the prior owner, it could be off balance with the blade that is more worn.

garye5007 · Aug 9, 2016

I'm so used to typing (") at work, I did it automatically That is Funny though!!

sweettractors · Aug 9, 2016

Sometimes if the blades get crossed and they will vibrate bad at startup and usually smooth out with increased rpm's. I do not know about yours specifically, however, most sheer bolts for rotary cutters are grade 3. Ken Sweet

TractorGuy · Aug 9, 2016

garye5007 said:
Hi,I have a Mahindra Max 25 Tractor and I picked up a 4" sundown brush hog (used) looks to be in pretty good shape. I didn't get a manual for it can't seem to find one online. I know very little about these things...
gearbox oil looks good (not milky)and it spins very freely. My questions are, 1.) is shakes.. I presume it's unbalanced. 2.)the blades attached to a stump jumper, are VERY dull. the nuts holding the blades to stump jumper are welded, is that normal? So to sharpen I figure I have to remove blade and jumper assy? How do I get this somewhat balanced when sharpening? One last thing, do I need a slip clutch? I don't have a clue what to get for bolts if I don't. Probably gonna have to hit you folks up for the adjusting everything to the tractor part in another thread.

Thanks in advance for any advice! Gary

Welded nuts are not normal. Do the blades still spin on the bolts? You may be looking at a new stump jumper and blades if you can't get it apart but I would torch or grind the nuts off and try to sharpen the blades and replace the fasteners. If it weren't for the vibration I wouldn't worry about the dullness if I were hogging brush. If you want to cut grass it will work better with sharper blades. You could probably weigh the blades on a set of bathroom scales to get it close enough to get the shake out if they spin as they are supposed to.

Shear bolts should work fine on the driveshaft. Most implements come with grade 2 I think but they break easy and are hard to get out because they stretch. I usually upgrade to grade 5. The gearbox risk is yours to take but in my experience the grade 5 bolts don't break often and they drive out easier when they do. I have not torn up a gearbox yet but not saying it won't.

sweettractors said:
Sometimes if the blades get crossed and they will vibrate bad at startup and usually smooth out with increased rpm's. I do not know about yours specifically, however, most sheer bolts for rotary cutters are grade 3. Ken Sweet

Not to nitpic but there are no "grade 3" bolts. bolt grades - Google Search

Grade 5 bolts are marked with 3 lines on them. Most grade 2 bolts have no marking.

garye5007 · Aug 9, 2016

Thanks alot for the replies!

JRobyn · Aug 9, 2016

To do a pretty respectable balance job on heavy blades like a lawnmower or bushhog, I clamp a reasonably sharp edge (edge UP) in a bench vise to use as a balance fulcrum. A utility knife blade does nicely. For the bushhog blades, you'll need to get them off and then hang one at each end of a stout balance beam and measure EXACTLY halfway in between the two hanging points. Attempt to balance this halfway point on the knife edge. You will find out right away if one is significantly heavier than the other! I grind material off the non-cutting part of the tip of the heavy one until they do balance.

A shear bolt will work fine on your modest-sized cutter if you don't beat it up too much. No need for a slip clutch.

Fallon · Aug 10, 2016

Sharp blades mean sharp stumps, which mean flat tires. Dull bars that shatter stumps & leave them fuzzy are your friend.

My LandPride usually shakes pretty good on startup. It smooths out after 10-20 seconds though. The bars should pivot around the mount, if not you have a problem. It let's them fold in a bit when hitting hard things. They also fold in when coming to a stop & unbalance everything. They straighten out, or at least should when coming up to speed.

kebo · Aug 11, 2016

A vibration could also be caused by something bent, not just an out of balance condition.

The safety police might jump in here but.... I would suggest that the OP park the tractor on level ground, put it in neutral,and engage the park brake. Then, get the blades to spinning (doesn't have to be full throttle here) with the bush hog raised a couple feet off the ground. Then, shut the tractor engine off and get back there and watch the pan and blades as they spin down. It should have enough momentum that it will keep spinning for a short while until it uses up that inertial energy. If you see any wobble with the pan or a blade, that could be the source of the vibration.

If you do that, just DON'T stick your head underneath the deck, just watch it from a couple feet away, and you should be able to do that safely without endangering yourself. If you aren't comfortable doing that, maybe you could set up a video camera underneath it and record it as spins down.

Let us know what you find out.