PT425 48" Brush Hog Broken Bolt Removal Tip

[ponytug]

Big blades = big energy. Great for reducing 4" oaks to chips. Also great for sending 10lb chunks a couple hundred feet. My wife now spots me from at least 350' away after one particularly large branch nearly hit her. Guesstimate was that she was 200' away at the time.

I think that the smaller blades may have impaired brush cutting performance, but might be somewhat safer to be near, rather like flails on a flail mower.

Just idle speculation...

All the best,

Peter

 

[MossRoad]

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.

Reviving an old thread....

After a couple more broken bolts, I, too, gave up and drilled a 1.5" hole through the top of the deck right in front of the hydraulic motor, in-line directly above the arc of the circle that the blade mounting bolts make, and use forceps to place a nut onto the back of the broken bolt and drive it out with the impact wrench. When I have time, I'll weld a nut to a bolt and do it that way. Much quicker. :thumbsup:

I'd still like to find a real 3 point hitch 48" brush hog and either adapt its guts (with better spindle and blade mounting system) to my PT brush cutter, or just remove it's 90 degree gearbox and drive it with my hydraulic motor from the PT brush cutter.

While the PT brush cutter is an absolute beast, I'm averaging one broken bolt for every 4 hours of operation, and its getting old.

 

[woodlandfarms]

My neighbor whom is a mechanic has a different solution I am considering. He wants to cut some wedges out of thick steel and weld them to the hub, so mini stump jumpers just before the blade. A wedge before each blade. Lots of physics I need to thing about on this.

I am not sure on this whole thing for a myriad of reasons. But I too am done with breaking bolts. Yeah, I would say one a day (so once very 8 hours of mowing) at the least.

 

[SpringHollow]

What size bolts are these? I know you can get button head up to 1/2" diameter, I am not sure about larger.

Ken

 

[ponytug]

Despite breaking a bolt every couple of hours before I changed my system, I haven't broken a bolt in five years.

I upgraded to Grade 8 shoulder bolts and sintered oil bushings. (McMaster) I remove the bolts, grease everything, and tighten it back up every eight hours. Greasing everything really improves the lifetime of my blades, as I am usually mowing in dry, gravel conditions that used to wear the bolt and bushing tremendously. An air wrench and welded steel sawhorses make quick work of it.

I gave up on trying to have the bolts in the holes 90 degrees from the blades. As Ken wrote above, I tried to find an oversize (buttoned) version that would match the PT blades, but I couldn't find one, nor could I find a set of "Brush Hog" original blades/bolts that would drop into the PT mower.

I'm on my fourth set of blades, though I am getting better at bending the blades back into shape. I just tried using my welder to fill the elliptical wear hole in one, and I think that I can rebuild most of my older blades by welding and grinding them. (Fun and games with a welder- I'm learning about what you can do with a TIG welder on a copper or aluminum surface.)

All the best,

Peter

 

[MossRoad]

Peter,
I would like to see some pictures if you have any. I also have two sets of bent blades somewhere (maybe I scrapped them already). I'm on my 3rd set in 15 years. And I only replace them because of the egg-shaped hole.

 

[woodlandfarms]

I made my own blades (or have them made I should say) by the local machine shop. they are 1/2" hardened steel. Not cheap, but I think comparable to PT.

Going to get a new set this year....

 

[ponytug]

MR- I just took a tip from a welding video (thank you youtube!) that used an aluminum plat to back up a weld. That gave me an idea to try. I put an aluminum plate below the blade, and then put a slightly undersized aluminum tube in the hole and worked my way in with a couple of layers of TIG. I originally tried tacking the bushing in place in an elliptical hole, but I didn't like the way it came out. If you are better than me with MIG, you could probably do it with MIG. It is way beyond my stick welding skills to try it, at least with a tube in the hole. I could imagine filling the hole in a couple of passes and then drilling a new hole.

I will need a drill press to get the hole back to size.

I used the same trick on the blade edge to lay down more material, and then ground it back down. I tried to be quick about it to not heat up too much of the blade.

Let me try to get photos.

All the best,

Peter

 

[MossRoad]

So the aluminum did not melt? It just acted as a form or guide for your steel welding?

 

[SpringHollow]

Copper and graphite work well for that purpose. For relatively small areas, you can just flatten out a small piece of copper pipe.

Ken

 

[ponytug]

Yes, yes, and yes.

The general idea is that you want the heat sink material not to be weldable under the conditions that you are welding. Since aluminum has a low melting point, you want the aluminum to be thick and large to absorb the heat and conduct it away fast enough not to melt.

Copper has a higher density and better thermal conductivity. I have a pair of copper "spoons" made of thick walled copper pipe for starting and ending TIG welds and to back holes to keep air from penetrating the welding areas. You can get fairly heavy pieces at scrap yards by looking for copper bus bars. I have heard of people using brass, but I have never tried it.

Graphite has the highest "melting point". I find it trickier to use, but your mileage will vary...

You can, of course, use this the other way around, e.g. using stainless steel to back up aluminum.

All the best,

Peter

 

[MossRoad]

Hmmm. If I would have attempted it, I guess I'd have just filled in the hole in the blade completely with the welder, ground it down flat, then drilled it out with a hole saw. I don't think balance is too critical on these beasts. I don't think I'd have to back the hole with anything. I'd stand the blade on edge and fill in the bottom of the round and work my way up. I've never tigged before. I've got an arc welder and wire-feed welder. I just use flux core right now. I've got a regulator, but never picked up a gas bottle. I think that might be handy to have VS the slag from the flux core in this situation. I'm planning on doing some body work on my old rusty Suburban, so maybe its time for gas.

 

[woodlandfarms]

So. Stupid me. Don't your guys mower blades have bushings? Mine is basically a piece of 3/4 pipe cut to size.

 

[ponytug]

They do have bushings, but un-greased you can wear through the bushing and into the blade in a day.
I upgraded to sintered, oil impregnated bushings, but greasing them is key for me.

All the best,

Peter

 

[MossRoad]

I've never thought about lubrication on those blades and bushings.... I will now, for sure.

 

[bol4fun]

First timer for changing a broken bolt. I luckily found the spacer, washer, and blade. I have read everything but not comprehending a lot. Where to start? ....big nut with cotter pin?.... 4 motor bolts? I am assuming that the drum on the under side has to come off. Any advice would be appreciated. Thanks

 

[MossRoad]

I bumped up an old thread in the PT forums for reference.

What I do to disassemble my brush cutter is (from memory):

- take off the 4 bolts that hold the motor mount bracket.
- loosen the allen set screw in the lovejoy
- lift the motor, bracket and half of the lovejoy off of the deck and set aside.
- I think there are 5 lug nuts that hold the hub assembly to the deck. Remove those 5 nuts and the entire hub, drum, and blade assembly will drop out the bottom of the deck.
- Lift the deck off of that assembly with the PT and back it out of the way, set down and continue.
- Now you have full access to the inside of the drum to work on the back-side of the broken bolt.

Hope that helps.

 

[MossRoad]

I eventually ended up using a hole saw and cut a hole in the top of the deck in-line with the rotation of the blade bolts. That allows me to stick a socket with extension down inside the back of the hub and remove the jam nuts to change out the blade bolts if they start looking damaged. This only works if the blade bolt head hasn't already sheared off. I kinda decided to just buy a box of blade bolts and change them once a year for good measure.

 

[woodlandfarms]

On my machine i cut holes in the deck to allow access to the threaded part of the bolt. My lock nutz are welded onto the drum so i made a long bolt with a nut partially threaded on and welded in place as a wrench. I line the broken bolt up with the hole and thread the bolt nut tool over the broken bolt and use my impact to drive it out far enough to grab with vice grips. Oh and i found for me grade 5 last longer than 8 as 8s are brittle and the bolts i use are longer than stock

 

[bol4fun]

I bumped up an old thread in the PT forums for reference.

What I do to disassemble my brush cutter is (from memory):

- take off the 4 bolts that hold the motor mount bracket.
- loosen the allen set screw in the lovejoy
- lift the motor, bracket and half of the lovejoy off of the deck and set aside.
- I think there are 5 lug nuts that hold the hub assembly to the deck. Remove those 5 nuts and the entire hub, drum, and blade assembly will drop out the bottom of the deck.
- Lift the deck off of that assembly with the PT and back it out of the way, set down and continue.
- Now you have full access to the inside of the drum to work on the back-side of the broken bolt.

Hope that helps.

Finally got around to working on the bolt. I bought my PT new in 2017 so the newer brush hogs are different. You don't have to take anything off the top of the unit. My son just took his impact gun and removed 5 bolts from the underside and it dropped down and we backed the bolt out with a vice grip. Easy Peavey!
The blades are bent a little so am taking them to a friend to see what his big press will do for them. Evidently the blades are made with a small bend at the ends because when I sat them on top of each other they are both the same????.....but need to work on the other bends. I sharpened them and now have to make sure I mount them in the right direction....forgot how they came off but think the unit revolves counterclockwise. Thanks for the tips