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I just want to say that my particular question doesn't have anything to do directly with the Ninja 300, its more of a general hardware question that may or may not pertain to us 300 owners. I am asking this here because I know there are some engineers and mechanics among us.

My question is, is there a torque limit or suggested range for Phillips head screws/bolts? For example, does a #2 Phillips head bolt have a published or known max torque that should be applied to them. I know they are designed to "cam out", but I haven't seen anything that says what torque a given size screw will do that at. The reason I ask is because I have to on a regular basis torque a countersunk 1/4-28 bolt to 75 in/lbs but with a fairly low success rate. I, and others tend to have about half of the bolts we put in cam out on us requiring them to be replaced and reattempted :(. The bolts are a steel alloy with a #3 Phillips head so its a pretty robust bolt. I end up changing the bit a lot to make sure it is "sharp" and have double checked all of them and the bolt data sheet to make I am using the right size so I know that's not the issue.

Do any of you mechanically inclined people out there have any input? Perhaps point me to a data sheet that tells me that the bolt should be able to do what I am asking of it or possibly the opposite. There are a few avenues I am looking to pursue with this but I want to try and build up some supporting material first before I try to get something changed.
 

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I expect that it would also depend on the hardness of the metal, so I don't think you'll be able to find a general number.
 

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Switch to a Robertson or hex screw to prevent it from caming out as easily. They are much better for high torque situations and are much less likely to strip
 

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Alot of times when torquing phillip or standard head screws/bolts to the higher in/lbs range that its not the torque that is stripping the head, but rather the pressure you put at a downward range not being enough to keep the screwdriver planted in the head of the screw/bolt. Also the angle one holds the screwdriver also makes a big difference. Even tho i've been wrenching for 35+ yrs I will still find myself in a hurry or can't hold the driver in a proper position to keep it seated and end up stripping the driver or the head of the screw/bolt.
Anyway, yes the hardness of the screw/bolt size and angle and number of threads is what determines the actual in/lbs to torque. There are tables out there you can download to tell you the general torque values of sizes and thread angle of most know bolts and screws.

one I just did a yahoo search on
http://www.engineershandbook.com/Tables/torque2.htm
 
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