QSC 8.3 Coupling Bolts

[Bobby Harvey]

Hi everybody! I have a QSC 8.3 500 HO driving a ZF 305 3A transmission. I’m trying to find 12 couplings bolts (and nuts). 5/8″ fine thread (18) x 2″ long – 12 point “extra hard”. Impossible to find (on this planet). Any help locating these would be appreciated.

Thanks everyone!

Bobby

 

 

Topic

[Bobby Harvey]

Thanks Gene. Very helpful information. I will go with this. 

 

[Clark Leighs]

Ensure the clamping faces of the flanges are free of any marks or raised area.   Likely not a problem but a light stoning with a watchfull eye for any raised spots.    Torque each bolt on opposites sides of the flanges and do it in several stages for the most even torque application.

[Gene Fuller]

The recommended torque for 5/8-18 (grade 8) bolts is on the order of 240 ft-lbs. Good luck reaching that torque in the cramped space available. Not easy! Any stronger bolts with a higher torque spec would be a waste of time.

Keep in mind that the role of bolts in this application is squeezing the flanges together, not by directly carrying the rotational load. The rotation load is carried by the friction between the flanges. Each properly torqued bolt provides over 20,000 pounds of compressive force, so the total friction between the flanges is very large.

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Tony Athens

[Bobby Harvey]

Thanks Tony. Rob is suggesting grade 8 bolts. That will simplify matters considerably. Do you agree? I’m not an engineer, couch or otherwise, I’m just a retired construction manager. LOL  I’m feeling my way through this yacht business with everyone’s help.

Bobby

[Bobby Harvey]

Thanks Rob. So you think grade 8 bolts will be good enough? I can find those all day long. I was trying to get the same ones that were originally on it, 12 point extra hardened, 5/8, 18 x 2″ long. But if grade 8 will be ok that makes it a lot easier. 

[Tony Athens]

ZF 305 Series Output Coupling

The bolt arrangement and coupling dimensions  , IMO, is a couch engineers wet dream.. Extremely difficult to deal with

[Rob Schepis]

McMaster-Carr has 5/8″-18 Grade 8’s in 2″ lengths.  Torque charts available on Google.  Be sure to grease them.

[Bobby Harvey]

QSC 8.3 Coupling Bolts – Torque Value

Also, I am having trouble finding out the torque value for these bolts. Can anyone help me with that as well?

Thanks again.

Bobby

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