PT425 48" Brush Hog Broken Bolt Removal Tip

MossRoad · Sep 4, 2012

Here's a trick that works well for me to remove a broken brush hog bolt on my PT425 48" brush hog.

I replaced the stock bolts with 2.5" bolts the first time they broke. That leaves about a 1.5" stub inside the hub. I use jam nuts and a wrench to back the broken bolt out from inside the hub.

It takes about 20 minutes if you use air tools and your compressor doesn't toss a belt, break its tensioning device and your kid doesn't spring a last minute 5 mile cross country training run on you that you have to follow on yuur bike. Then it takes 4 hours.

cqaigy2 · Sep 4, 2012

MossRoad said:
Here's a trick that works well for me to remove a broken brush hog bolt on my PT425 48" brush hog.

I replaced the stock bolts with 2.5" bolts the first time they broke. That leaves about a 1.5" stub inside the hub. I use jam nuts and a wrench to back the broken bolt out from inside the hub.

It takes about 20 minutes if you use air tools and your compressor doesn't toss a belt, break its tensioning device and your kid doesn't spring a last minute 5 mile cross country training run on you that you have to follow on yuur bike. Then it takes 4 hours.

Lol, sounds like one of my typical projects. Nice mod.

KMA · Sep 4, 2012

I replaced mine with grade 8 bolts a while back. I also picked up some tire retread off the highway and cut some pieces and added them onto the stop bolts for shock absorption. Hopefully they won't break on me, but I think they protrude slightly into the hub like yours so your trick would come in handy... not sure I would have thought of it myself. Nice job. :thumbsup:

Clumber · Sep 4, 2012

KMA said:
I replaced mine with grade 8 bolts a while back. I also picked up some tire retread off the highway and cut some pieces and added them onto the stop bolts for shock absorption. Hopefully they won't break on me, but I think they protrude slightly into the hub like yours so your trick would come in handy... not sure I would have thought of it myself. Nice job. :thumbsup:

I am assuming that grade 8 bolts have more shear strength? Do you have a photo showing the rubber attached to the bolts? I thought of doing that but I thought the bolt would protrude into the blade path...

Anyway, great ideas guys.

KMA · Sep 4, 2012

Yeah, the grade 8 bolt has more tensile strength and shear strength is a percentage of tensile I believe (not an expert though). Unfortunately I don't have a photo right now of the rubber on the bolts. The retread I happened to pick up was about 3/4 inch thick and had a sort of hexagon pattern that I followed when cutting chunks out. Once mounted, there was approximately a 3/4 inch of material around the stop bolt. I cut them out, drilled holes and added them as if they were washers. I haven't checked them lately to see how they were holding up. I always throttle down before turning on PTO with the brush cutter so the blades don't whip back as hard against the stop bolts.

MossRoad · Sep 4, 2012

This last time I switched to grade 8. We'll see how that goes.

The thread on the 2.5" bolts does not go all the way to the head, which requires the addition of some flat washers. I use three on the bolt, then the blade with bushing, then one more washer between the blade and the bottom of the drum. It ads about a 1/4" to the length that sticks down under the blade. I've been doing this for many years and the washers take a beating. I am finding that if I hit stumps with the blades and back off, nothing bad happens. However, if I progress forward and hit the stump with the bolts, I tend to cause damage to them. Each time I break a bolt, I remove the one that did not break also and inspect it. It is always bent. I wish there was a way to make the blades lower than the bolt heads that hold them on. Gull wing blades, perhaps??? :confused3:

SpringHollow · Sep 5, 2012

I may be way off here but hardened metal is pretty brittle usually. Very strong in tensile strength but I would think a grade 8 bolt will snap when a grade 3 would bend. So, personally, I would not recommend going to grade 8. But maybe I am all wrong.

Ken

woodlandfarms · Sep 6, 2012

I break on average 6 bolts a year. loose 2 blades a year. Want a metal detector but... PT's design to attach blades is truly worthless. I decided to completely go without bumpers, removing the bolts in the spare holes and putting in hex plugs. My neighbor and I have discussed in detail mods to the mower to make the blades less fragile.

Any mod seems to open me up to maybe inbalancing the system. And I have tried every bumper idea there is (From a stack of soft washers to a hockey puck to a tire peice) and none of those work.

For the 1850 taking the mower drive spool out is a PITA. I am perfecting the art of welding a nut to the broken bolt. I have one that refuses to come out. This winter I will pull the spool. I am trying to see if I can put in an acess panel from above to allow me to remove those broken bolts.

I have been running grade 8s for a while. I have no clue if they are any better or worse. I am moving back to 3's just because I don't sense a difference.

SpringHollow · Sep 6, 2012

I broke my first one just a month ago (I only use the bush hog a few times a year right now) and used a metal detector wand used for finding nails in wood to recover my parts. It broke when the head hit a rock and I have not tried removing the bolt yet. I broke one blade a couple of years ago and never found one half. It was near the house - kind of scary.

Ken

MossRoad · Sep 6, 2012

This is the first time I am trying grade 8. I will let you all know how it works out in the future. I will not be brush hogging again, to my knowledge at least, until next spring.

On the subject of locating lost blades/parts... a LONG time ago I bought a toy metal detector from Radio Shack for under $20.00 when I lost some keys in the snow. It found them pretty quickly. Guess what? It works great on large metal objects like brush hog blades buried under an inch of sand, dropped car keys in snow piles, dropped drill bits in grass, etc... Radio Shack does not seem to carry that model any more, but I found these that look very similar to what I have. For under $30.00 it is a fun toy and actually usefull.
If you don't like it, give it to a kid!
Elenco Metal Detector With Beep Alert: Amazon.com: Sports & Outdoors

PTWannaHave · Sep 6, 2012

Since I am not familiar with the issue, the following is an observation more than a suggestion...

If I understand the problem correctly, hex bolt heads get severely damaged or sheared off by hitting something hard at high velocity. The rest of the bolt remains in the welded nut, and can be very difficult to remove. (This is a royal PITA.)

I have a blades for my mower that look like a bush hog setup. Basically, short blades that are free to swivel, attached at one end to the edge of a disc. (Four blades per disc.)

These blades are attached with a Button Head bolt (a.k.a. Round Head). These bolts usually have a hex drive or Torx drive hole in the head. Using such a bolt greatly minimizes 'catching' the ground, as the dome has a much better chance/tendency to 'float over' obstacles.

1/2-20 BUTTON HEAD SOCKET CAP SCREW, Each - Palmer Bolt & Supply Co.

Cheers,

woodlandfarms · Sep 6, 2012

we have reviewed the button head idea on my end and in the end I walked away. I might revisit. Reason for walking away is that the hex portion tends to get bent up, not allowing a hex key to fit in to loosen and remove the blade without substantial work. Now, this is just theory and conjecture but it might take a long time to file the opening on the bolt to get a hex back in. But in its defense I have only once taken a blade off, and that was when a spindle was having an issue. Otherwise I just wait for them to break away.

Second, I am not sold it is only the head that is an issue. while the cutting edge provides a ramp of sorts, the end is blunt, i have broken on small stumps, and y tought was that the blad gets wacked back and on the next time around its blunt end stikes the object.... Theory again.. Probably the blade is staightened out within a half turn of the rotor...

But you know what, why not, right? Next time I am in Woodland I will pick up a bag and give them a try if they make them in our size.

Carl

MossRoad · Sep 6, 2012

How are "regular" brush hog blades attached on "regular" tractors? Do they have the same breakage issues?

MossRoad · Sep 6, 2012

O.K. So here's the real problem as I see it. EVERY brush hog that I can find on the internet has GULL-WING BLADES!!! Meaning, the blades have a bend in them so that when the blade comes around after hitting an object it cannot shear off it's partner's bolt!!!

AND, the center drum on EVERY brush hog I can find on the internet is a LOT SHORTER than the PT design, which allows for the dip in the blade. If you tried to put gull-wing blades on a PT brush hog, you would gouge the ground pretty good, even with the wheelsl set on the highest setting.

Someone (Power Trac, are you listening?) needs to come up with a retrofit kit that makes the drum shorter by an inch and a half so that we can put gull-wing style blades under it and resolve this terrible design/saftey issue.

There, I feel all better now and will stop using CAPS in my post.

cqaigy2 · Sep 6, 2012

hmmm i may just have to try those out.

BobRip · Sep 7, 2012

Could you change the wheel brackets so the mower could be raised higher or would that allow the blades to be too exposed?

MossRoad · Sep 7, 2012

BobRip said:
Could you change the wheel brackets so the mower could be raised higher or would that allow the blades to be too exposed?

Yeah, I think it would expose the blades too much. It needs a shorter drum. The current one is HUGE. I could probably cut two inches off of it and shorten the shaft, then put on the better blade style. Hmmmm..... DANG! Got me thinking again of projects I don't have time to complete!!!! :mur:

:laughing:

MossRoad · Sep 15, 2015

Had to replace a blade again today. I knocked it off in the spring and now its firewood season, so had to put it back on so I can clear my logging trails. The two jam nuts on the backside did the trick nicely again to get the broken 2.5" bolt out after the head snapped off.

I made my own spacers that go inside the blade holes out of DOM tubing that I bought from On Line Metals last year. That saved quite a few dollars, as I can probably get 20 or more spacers out of a 12" piece.

Order Mild Steel A513 Tube in Small Quantities at OnlineMetals.com

Still haven't had the time to investigate retrofitting a "normal" brush cutter head and blades to the underside of the PT deck. I've been looking at bush hog brand decks, and this parts diagram in particular, for ideas. Sounds like a winter project.
http://www.bushhog.com/uploads/documents/BHRotaryCuttersq36-sq84oldPM-03.pdf

woodlandfarms · Sep 15, 2015

Moss, on your PT how do you reach these nuts? Do you have to drop the Spindle?

I am not sure if I reported this but last year I cut a bunch of holes in my deck (3 to be exact plus 3 drain holes) These holes allow me to use a rig I made (A nut welded onto a long bolt with just a bit of thread hanging out). I rotate the spindel so that the broken bolt is visible through the hole in the deck. I then thread the long bolt with welded nut onto the existing nut. Slap on my impact wrench and down it goes. I then lif the mower and grab on with vice grips and spin the broken bolt out. Right now I am averaging around 5 or 6 broken bolts a year (I am continuing to push back the blackberries and brush and there is always something noisy and sparky and fun to hit buried within). I have to get a metal detector.

Oh, as for spacers on my machine I am just using 3/4" black pipe. Seems to work fine for my system.

MossRoad · Sep 15, 2015

Yeah, I've read about those holes you drilled. Sounds interesting. I just take an air impact wrench and a crescent wrench and remove the two hydraulic motor bolts and get that out of the way. The upper lovejoy section stays on the motor shaft. Then I loosen the allen screw on the lower lovejoy section. Then the impact wrench on the 5 lug bolts and the whole spindle drops to the ground. I stand between the two front wheels, grab the caster arms, do my best Bill Kazmaier impersonation, and lift the deck up and walk it backwards to get it over the spindle.

That whole process only takes about 5 minutes. Then I just back the broken bolts out the rear with those jam nuts and a crescent wrench.

To put it back on again, I just to it in reverse order. If all goes well and I have all the parts, its 15-20 minutes.

I'd rather convert it to a design where the blades can't whack each other's mounting bolts and be done with it.

I have to wonder, though, about blade length. The PT design has long blades and a narrower center drum. The bush hogs I've been looking at have short blades with wider center drums. The blades are gull winged and since they are also short, they can't hit the other blade or blade bolts. But I wonder if the shorter blades have the knock down power of the longer PT blades? I'd hate to convert it only to realize I can't destroy brush as well as the PT does now.

This time I did put in 2.5" bolts with long spacers in the spare holes on the drum. I'm hoping I can sacrifice those and they'll stop the blade from hitting it's partner's mounting bolt. They look to be down a bit lower than the blade bolt heads. I'm guessing they'll hit some rocks or stumps before the blade mounting bolts and I'll hear it and back off before the damage is done. I'll give it a test later this week or weekend and see how it goes.