Multi-Tip Or Green Teeth Stump Grinder Cutting Wheel? What's Your Experience?

[Gardenequipment]

For the last few years I have been using a Predator stump grinder. My present stump grinder is a 38 RX fitted with a Kohler EFI engine, a big improvement on the petrol carburettor version and the Lombardini diesel engine.

 

The cutting head is really my only gripe. I've always been very satisfied how well the Multi-Tip cutting head performs and how easy it is to change the teeth. However, an issue that always seems to arise is the shearing off of the bolt holding the cutter teeth in place.

 

According to Predator a few years ago there were a few soft steel cutting wheels around which were causing issues. They actually gave me a free replacement cutting wheel. After approximately 15 hours work with my latest Predator, I sheared my first bolt. I can break sometimes three or four bolts in a days grinding and sometimes I won't break a single bolt for several days. I'm not quite sure why this is, however, I do believe that the cutting wheel steel is not particularly hard, therefore the pockets become slightly stretched.

 

I'm thinking about possibly changing to a Green Teeth cutting wheel, I would be interested to hear about other people's experience with the above cutting wheels.

 

You can read more and see a short video on a post that I wrote a few days ago.

 

Thank you for reading.

 

Roy

[lux]

For the last few years I have been using a Predator stump grinder. My present stump grinder is a 38 RX fitted with a Kohler EFI engine, a big improvement on the petrol carburettor version and the Lombardini diesel engine.
 
The cutting head is really my only gripe. I've always been very satisfied how well the Multi-Tip cutting head performs and how easy it is to change the teeth. However, an issue that always seems to arise is the shearing off of the bolt holding the cutter teeth in place.
 
According to Predator a few years ago there were a few soft steel cutting wheels around which were causing issues. They actually gave me a free replacement cutting wheel. After approximately 15 hours work with my latest Predator, I sheared my first bolt. I can break sometimes three or four bolts in a days grinding and sometimes I won't break a single bolt for several days. I'm not quite sure why this is, however, I do believe that the cutting wheel steel is not particularly hard, therefore the pockets become slightly stretched.
 
I'm thinking about possibly changing to a Green Teeth cutting wheel, I would be interested to hear about other people's experience with the above cutting wheels.
 
You can read more and see a short video on a post that I wrote a few days ago.
 
Thank you for reading.
 
Roy

I have the same grinder. Have you tried buying bolts from elsewhere or even had some produced. Looks like the bolts are made from the wrong steel for impact work.

[Nick Connell]

Maybe a dodgy batch. We only seem to break a bolt when the tooth is loose.

[Gardenequipment]

1 hour ago, lux said:

I have the same grinder. Have you tried buying bolts from elsewhere or even had some produced. Looks like the bolts are made from the wrong steel for impact work.

Thank you for your reply, it is appreciated. I purchased the bolts from the dealer, so I'm assuming that they are the correct bolts. I may try sourcing bolts from somewhere else, just to make sure though. They have 10.9 stamped on the top which I believe is the hardest bolt.

[Gardenequipment]

8 minutes ago, Nick Connell said:

Maybe a dodgy batch. We only seem to break a bolt when the tooth is loose.

Thank you for your reply Nick, it's appreciated. It's strange how sometimes I can break three of four bolts a day and then go for several days without any issues. It does make me wonder if the bolts aren't up to spec. I do find that the pockets do become more slack with wear and tear, which makes me wonder if the wheel isn't hardened correctly. 

[openspaceman]

21 minutes ago, Gardenequipment said:

Thank you for your reply Nick, it's appreciated. It's strange how sometimes I can break three of four bolts a day and then go for several days without any issues. It does make me wonder if the bolts aren't up to spec. I do find that the pockets do become more slack with wear and tear, which makes me wonder if the wheel isn't hardened correctly. 

Looking at your photo of the snapped bolt there is what appears to be a fatigue crack developed from the thread root which then causes the bolt to fail in tension. Can you get a bolt with a longer none threaded shank?

 

I had a similar but not frequent problem with the Plaisance mulcher where the bolt would snap and the bolt head then fly off, followed by the tooth if I didn't notice the problem. It was caused by the pocket being worn and the cutter could rock very slightly fore and aft flexing the bolt head and  eventually snapping. The Plaisance bolts did not directly hold the tooth in as yours do.

Edited October 25, 2020 by openspaceman
typo

[Gardenequipment]

8 hours ago, openspaceman said:

Looking at your photo of the snapped bolt there is what appears to be a fatigue crack developed from the thread root which then causes the bolt to fail in tension. Can you get a bolt with a longer none threaded shank?

 

I had a similar but not frequent problem with the Plaisance mulcher where the bolt would snap and the bolt head then fly off, followed by the tooth if I didn't notice the problem. It was caused by the pocket being worn and the cutter could rock very slightly fore and aft flexing the bolt head and  eventually snapping. The Plaisance bolts did not directly hold the tooth in as yours do.

Thank you for your reply, it's appreciated.

That's a good thought regarding the threaded bolt, I will find out. I believe the problem may be caused by the cutting wheel, almost stretching and making the teeth fractionally loose. I'm guessing if the cutting wheel isn't hardened properly it will enable the teeth and the holders to move. It's a time-consuming issue, especially if it happens several times in a day.

Were you able to cure the issue you had with your mulcher? That doesn't sound good with lumps of metal flying around in a flail!

[Will C]

I’ve not sheared one of them in over 5 years, multi tip are a good set up, I’ve smashed the odd tooth but never had a bolt go.

there are two things I can think of.

1- are you knocking the teeth and the holder the bolt goes through back hard to the wheel? Tighten them up then hit them back again with a hammer and punch, they will move a few mm but this gives you another 3/4 turn on the bolt and they don’t come lose. your wheel doesn’t look worn, they normally wear a semi circle on the corner under the tooth as it starts to wear

 

2- Check the threaded pocket Is flush with the flywheel when you tighten it up and it’s not that getting hit from the side that’s effecting the bolts.

[Will C]

@Gardenequipment just another thought. What are you doing the bolt up with? They only need a long Allen key not a 2ft breaker bar. (Don’t mean to sound condescending) ??

[openspaceman]

10 hours ago, Gardenequipment said:

Were you able to cure the issue you had with your mulcher? That doesn't sound good with lumps of metal flying around in a flail!

The only solution was to cut the old pockets off the rotor and weld on new ones, it was a poor designe compared with the Awhi.

 

@Will C seems to have a handle on it, making sure the wheel is cleaned of any debris so the cutter seats well.

 

Also if they are allen bolts 12.9 are the strongest.