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

[dan blocker]

I run a Predator 28 and have never had a bolt break - that statement is probably the start of it now! Do you clean the pockets of all grime and muck and dress off any burrs with a file - just the minimum, otherwise you can torque a false reading and it all slackens off, I think a slack bolt is more likely ro snap than a tight one?. I’m sure you do all of this but just covering it?

[Gardenequipment]

22 hours ago, Will C said:

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.

Thank you for your reply Will, it's appreciated.

That's amazing that you haven't sheared a bolt in five years, I'm amazed that I haven't sheared a bolt in seven days, that's almost a record for me! I really like the Multi-Tip set up, I have used finger teeth and green teeth in the past, however, Multi Tip is my preferred setup. It's just frustrating with the bolts shearing.

I like your idea of driving the teeth and the holder right home, this sounds like a good idea. I'm aware that dirt can also become embedded in the pockets and cause the teeth to to not tighten fully. I will give your idea a try, thank you.

I hear you regarding your second point, I will check this out.

I actually used the torque wrench to tighten up the bolts that came with my original machine.

I still wonder if my cutting head has been hardened properly as it almost appears that the wheel is slightly stretched. In other words, when the wheel is new, the teeth and pocket seem to fit nice and snugly, as time goes on the slots on the wheel seem to open up fractionally causing a fractional bit of play.



 

[Will C]

To drive them home I give it a knock each side of the bolt on the holder and a good knock between the teeth on the body of the tooth. I’ve not used a torque wrench with them, just a long Allen key!

[Gardenequipment]

13 hours ago, openspaceman said:

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.

It's a shame when manufacturers design something poorly, it can cause a lot of frustration and aggravation.

I hear you regarding the cutter wheel being clean, this could make the difference between shearing a bolt and not shearing a bolt!

I hear you regarding the 10.9 bolts, they are the hardest. Although a few people have mentioned to me in the past that a softer bolt may be more flexible, just a thought.

[openspaceman]

43 minutes ago, Gardenequipment said:

I hear you regarding the 10.9 bolts, they are the hardest. Although a few people have mentioned to me in the past that a softer bolt may be more flexible, just a thought.

It's not hardness you need but rather toughness and tensile strength.

 

Normal bolts tend to be 8.8, the next common stronger ones are 10.9 and the highest tensile strength is 12.9, countersunk ones seem to be limited to 10.9 although some sellers do claim 12.9.

[lux]

As already mentioned torque settings will be critical. On both my grinders once I have tightened them up I rotate the cutter and give each pocket a couple of knocks with a hammer then recheck. Usually grit / dirt moves and they need a nip up to torque again. Seems to work for me [emoji106]

[Gardenequipment]

On 27/10/2020 at 08:08, openspaceman said:

It's not hardness you need but rather toughness and tensile strength.

 

Normal bolts tend to be 8.8, the next common stronger ones are 10.9 and the highest tensile strength is 12.9, countersunk ones seem to be limited to 10.9 although some sellers do claim 12.9.

I'm pretty sure the bolts that I use say 12.9 on them, I will check though.

[Gardenequipment]

Thank you for all your comments and thoughts, they are all appreciated.

Just for your interest, when I replace a set of teeth I am now taking extra care to thoroughly clean out the pockets etc. I did this before, however, this time I'm taking extra care. I'm also using a centre punch to push the teeth in slightly further once I have tighten the bolt. (As suggested in this thread.) This seems to enable me to tighten the bolt a bit more, which so far seems to be working, which is great news!

So far I haven't broken a bolt for two weeks which is great, in fact, it's exceptionally good going for me! I hope this carries on.

Once again thank you for your help.

Roy

[herco]

On 27/10/2020 at 07:47, Gardenequipment said:

Thank you for your reply Will, it's appreciated.

That's amazing that you haven't sheared a bolt in five years, I'm amazed that I haven't sheared a bolt in seven days, that's almost a record for me! I really like the Multi-Tip set up, I have used finger teeth and green teeth in the past, however, Multi Tip is my preferred setup. It's just frustrating with the bolts shearing.

I like your idea of driving the teeth and the holder right home, this sounds like a good idea. I'm aware that dirt can also become embedded in the pockets and cause the teeth to to not tighten fully. I will give your idea a try, thank you.

I hear you regarding your second point, I will check this out.

I actually used the torque wrench to tighten up the bolts that came with my original machine.

I still wonder if my cutting head has been hardened properly as it almost appears that the wheel is slightly stretched. In other words, when the wheel is new, the teeth and pocket seem to fit nice and snugly, as time goes on the slots on the wheel seem to open up fractionally causing a fractional bit of play.



 

Also never sheared a bolt of, Just use 8.8 one's. On predator 75.

Its all in the proper mounting and torquing.

Well a lot of broken of tips and execcisive waer on some teeth.

Last 3 changes welded some abrasive site on Them winch seems tot help.

[allseasons]

9 hours ago, Scottish Cleaning Service said:

Has anyone used one of these, quite heavy but look good on utube.

We had one and sold it to wide for doorways and hard work to use. Teeth dont last and expensive