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Question on bolt torque

capetrees

capetrees

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I've replaced the blades on my chipper numerous times and every time I've changed them, I need a pipe extension on the breaker bar to loosen the bolts. I've always torqued them with the same torque wrench over the years. I've, by chance, always removed and replaced the bolts when the drum is room temperature. Never had a problem.

I came back to the shop after working and chipping all day and decided to change the blades. I opened the lid and came to realize the chipper drum was hot, obviously form working it less than an hour prior. I went to remove the bolts and when I did, they backed out relatively easy, no need for an extension pipe and no usual "bink" as the bolt breaks free, just a simple amount of pressure with the breaker bar.

My question is, is this normal? Do the torqued bolts back out easier if they're warm/hot? And after they're out, should I wait till the drum cools down to room temperature before putting the new blades on and torqueing the new bolts down? If I do it when the drum is warm/hot, will they loosen later on down the line when the drum cools down? Or should I wait till the drum cools down and then install the new bolts to the proper torque? Or does any of it matter at all?
 
Rennsman

Rennsman

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How old are lock washers?

It is of note that the standard lock (spring, helical, split) washer is not generally considered effective for use in preventing loosening of a fastener, it can in light duty applications help after loosening has occurred.

It can even increase loosening over standard plain flat washers, many bolted connections would probably be better off with standard flat washers over helical spring lock washers.

The word lock is mostly a historical hangover term for the spring washer.

Nord-lock type washers are what is called for if a locking action is desired from a washer.
 
mrhemihead

mrhemihead

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To adjust the shear bar on my BC1000XL a 4' breaker bar was needed for the first bolt. (same size as the blade bolts).
For the remaining bolts a late model Milwaukee cordless 1/2" impact wrench was used. The bolts backed out without much effort.
Next time when the blades need changed I will try the impact wrench.
 
capetrees

capetrees

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To adjust the shear bar on my BC1000XL a 4' breaker bar was needed for the first bolt. (same size as the blade bolts).
For the remaining bolts a late model Milwaukee cordless 1/2" impact wrench was used. The bolts backed out without much effort.
Next time when the blades need changed I will try the impact wrench.
and then torqued properly when reinstalled.

Interesting that the other bolts didn't need the breaker bar.
 
lone wolf

lone wolf

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and then torqued properly when reinstalled.

Interesting that the other bolts didn't need the breaker bar.
I cant imagine enough heat being there from use it wasnt like you used a torch. Just do what you always do they held so far. If you are worried buy new bolts becuase they can stretch if over torqued . I have a Bandit and just run them down with a half inch air impact gun , but I don't go ape **** on them because they could weaken and break.
 
capetrees

capetrees

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I cant imagine enough heat being there from use it wasnt like you used a torch. Just do what you always do they held so far. If you are worried buy new bolts becuase they can stretch if over torqued . I have a Bandit and just run them down with a half inch air impact gun , but I don't go ape **** on them because they could weaken and break.
I plan to just keep torqueing them when the drum and block are cooled to room temp. Never had a problem. (edit) I was originally just wondering if there would be a difference in the torque if I installed the bolts while the drum and blocks were warm/hot. Would they become less torqued or more torqued when the unit cooled down.
I only use the bolts once due to an incident once where the bolts broke on a rental unit. Those bolts were used at least twice by the rental agency AND had blades as sharp as your thumb. Bolts broke, blades went flying, lucky nobody was hurt or killed. Since then, even though it says they can be used twice, I use new bolts every time I swap the blades over. For the price of 8 new bolts compared to $6K to replace the drum, bearings, blades bolts and of course labor? Bolts are new every time.
 
dboreham

dboreham

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I plan to just keep torqueing them when the drum and block are cooled to room temp. Never had a problem. (edit) I was originally just wondering if there would be a difference in the torque if I installed the bolts while the drum and blocks were warm/hot. Would they become less torqued or more torqued when the unit cooled down.
I only use the bolts once due to an incident once where the bolts broke on a rental unit. Those bolts were used at least twice by the rental agency AND had blades as sharp as your thumb. Bolts broke, blades went flying, lucky nobody was hurt or killed. Since then, even though it says they can be used twice, I use new bolts every time I swap the blades over. For the price of 8 new bolts compared to $6K to replace the drum, bearings, blades bolts and of course labor? Bolts are new every time.
There wouldn't be a difference in torque because the torque was applied by a wrench that was at calibrated temp, or close to. But that's not the point because bolt torque is a proxy for the tensile stress applied to the bolt head vs its threads and I would suspect the relationship between the two may change with temperature similar to how it changes when lubrication is applied. Since the bolts are $3 ea, and the consequences of bolt failure are serious, personally I wouldn't take chances. I bought a box of the bolts from McMaster. Also worth noting that Vermeer manual says not to use impact wrenches on these bolts. It doesn't say why but perhaps out of concern that the bearings could become damaged?
 
mrhemihead

mrhemihead

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and then torqued properly when reinstalled.

Interesting that the other bolts didn't need the breaker bar.

There wouldn't be a difference in torque because the torque was applied by a wrench that was at calibrated temp, or close to. But that's not the point because bolt torque is a proxy for the tensile stress applied to the bolt head vs its threads and I would suspect the relationship between the two may change with temperature similar to how it changes when lubrication is applied. Since the bolts are $3 ea, and the consequences of bolt failure are serious, personally I wouldn't take chances. I bought a box of the bolts from McMaster. Also worth noting that Vermeer manual says not to use impact wrenches on these bolts. It doesn't say why but perhaps out of concern that the bearings could become damaged?
Thanks for the FIY on McMaster, I have been paying way too much for these bolts.
The Vermeer BC1000XL service manual mentions "to prevent bolt damage not to use an impact wrench for installing knife/drum bolts". For sure there is no way to get accurate torque settings with an impact wrench.
 
Jedthro

Jedthro

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Thanks for the FIY on McMaster, I have been paying way too much for these bolts.
The Vermeer BC1000XL service manual mentions "to prevent bolt damage not to use an impact wrench for installing knife/drum bolts". For sure there is no way to get accurate torque settings with an impact wrench.
Just FYI, the specs claim +/- 10%

 
capetrees

capetrees

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Just FYI, the specs claim +/- 10%

I'll stick to my manual torque wrench. My bolts need to tighten to 210 lbs and according to the charts, those adapters are accurate to within 10% so I could over tighten to 230 or under to 190.
 
dboreham

dboreham

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"to prevent bolt damage not to use an impact wrench for installing knife/drum bolts". For sure there is no way to get accurate torque settings with an impact wrench.
Interesting. I hadn't noticed the text relating to bolt installation (who would try to torque a critical bolt with an impact wrench?), but it also says : "To prevent damage, do not use impact tool to remove bolts". That was the part I was thinking of above.
 
capetrees

capetrees

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I'm thinking the trick here is to use the best of both worlds. Remove the bolts when they are warm and then install when the system is back to room temperature.
 
lone wolf

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Interesting. I hadn't noticed the text relating to bolt installation (who would try to torque a critical bolt with an impact wrench?), but it also says : "To prevent damage, do not use impact tool to remove bolts". That was the part I was thinking of above.
Sounds they had lots of trouble with this system if they are warning against removing bolts with an impact gun WTF?
 
mrhemihead

mrhemihead

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Sounds they had lots of trouble with this system if they are warning against removing bolts with an impact gun WTF?
This poster may have a different Vermeer manual. The version I have states "do not to use a power or impact tool to install knife/drum bolts".
Nothing more on this in the manual.
 
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