bolt grading question

[Sawyer Rob]

The bolts were stretching and then the blades were loose and soon getting tore off. Quality bolts fixed the problem!!

SR

 

[SPYDERLK]

The bolts were stretching and then the blades were loose and soon getting tore off. Quality bolts fixed the problem!!

SR

Do you have a couple of those counterfeit bolts left? Could you send me a couple? Its a serious liability concern to sell substandard hi grade bolts and should be taken up with the supplier.
,,,
larry

 

[Sawyer Rob]

NO and HE!! NO! I can't tell you how much grief they caused me!

The blades came loose, so i then torched the heads off and replaced them with GOOD bolts! This on jobs 50 miles away from my shop, so you know how much fun i was having!!

I had other occasional bolt problems from them, but i never put it together until that happened.

SR

 

[Mark @ Everlast]

I keep a generous supply of bolts around. Unless it is a shear pin for a rotary cutter or similar application, I stock/use nothing less than grade 5. I also use grade 8 in a few applications, and even have a handful of L9's. Worse thing to do is put the wrong shear bolt in a rotary cutter. Most recommend a grade 2, but a couple recommend a grade 5. I've seen many a detonated gear box because someone "upgraded" their shear bolt because they got tired of replacing them.
As far as bolts go, most, if not all are imported these days. Quality does matter. Bolt heads contain a good bit more information than the average person realizes. Each bolt brand has a distinctive trade mark which can be traced back to the manufacturer. Bolt distributors worth their salt have documentation back to the factory so that if a fastener fails, ie. an airplane, it can be traced back, batch lot checked etc., with the ultimate blame resting on the manufacturer of the bolt.


As far as the TM's I found a list here: 404 error - page not found | USPTO

Anyone recognize any of their favorites?

It says error page not found but the link works for me.

 

[muddstopper]

Bolt shear strength is measured at least 2 different ways, according to how the bolt is used. Single shear would be like bolting 2 pieces together with stress pulling opposite directions on each piece. Double shear (think PTO pins), would be like bolting three pieces of metal together with the middle piece being pulled one way and the outer 2 pieces being pulled the opposite direction. A grade 8 bolt would have about twice the shear value of a grade 2 bolt, but only slightly more than a grade 5. A a307 is a little less than a grade 2 bolt and is what is normally used as a shear pin, so a grade 2 bolt would be an upgrade to a normal shear pin.

 

[LD1]

If just doing general building and fabbing, grade 5 is fine. Grade 8 and alloy bolts are usually overkill unless spec'd to need the strength. Good reaason for grae 8 or allow bolts is greater torquing, therefore greater clamping ability. Same can be said for fine thread. But there are times where grade 8 is just too hard. Certain suspension components and u-bolts come to mind. But in general, if you are designing and building stuff, it is typically cheaper to upsize and use grade 5 vs grade 8

Much stronger to withstand and spread hi bolting loads.

They also make heavy hex bolts and nuts that take larger wrenches than normal for the size. Helps spread holding pressure over a greater area for things like flanges on airlines or other pressure things

 

[jb1390]

Bolt shear strength is measured at least 2 different ways, according to how the bolt is used. Single shear would be like bolting 2 pieces together with stress pulling opposite directions on each piece. Double shear (think PTO pins), would be like bolting three pieces of metal together with the middle piece being pulled one way and the outer 2 pieces being pulled the opposite direction. A grade 8 bolt would have about twice the shear value of a grade 2 bolt, but only slightly more than a grade 5. A a307 is a little less than a grade 2 bolt and is what is normally used as a shear pin, so a grade 2 bolt would be an upgrade to a normal shear pin.

There's a nice chart here on bolt strength capabilities by size and grade-both in tension and shear.

Grade 5 vs Grade 8 Fasteners - TineLok

One aspect to be careful about is when you side load a tightened fastener (think shear), you are also pulling against the friction that the clamping of the bolt provides. A pure friction joint will use enough bolts that the clamping load will be enough to cause none of the bolts to be loaded in shear. For this reason, don't ever tighten your shear bolts!!! Use a lock nut and run them loose.

 

[jb1390]

If just doing general building and fabbing, grade 5 is fine. Grade 8 and alloy bolts are usually overkill unless spec'd to need the strength. Good reaason for grae 8 or allow bolts is greater torquing, therefore greater clamping ability. Same can be said for fine thread. But there are times where grade 8 is just too hard. Certain suspension components and u-bolts come to mind. But in general, if you are designing and building stuff, it is typically cheaper to upsize and use grade 5 vs grade 8



They also make heavy hex bolts and nuts that take larger wrenches than normal for the size. Helps spread holding pressure over a greater area for things like flanges on airlines or other pressure things

An interesting note about fine thread fasteners - the pitch actually doesn't help increase the clamping load directly. The reason a fine thread will hold more than a coarse thread is the minor diameter is larger for fine thread - hence a larger cross sectional area within the same size clearance hole, so you can torque to a higher value. It's a way of getting a "bigger bolt" when you don't have space to accommodate a bigger bolt.

 

[SPYDERLK]

An interesting note about fine thread fasteners - the pitch actually doesn't help increase the clamping load directly. The reason a fine thread will hold more than a coarse thread is the minor diameter is larger for fine thread - hence a larger cross sectional area within the same size clearance hole, so you can torque to a higher value. It's a way of getting a "bigger bolt" when you don't have space to accommodate a bigger bolt.

Well, yes, but/and the finer pitch has a more gradual advance hence more mechanical advantage. The same torque will give a slightly higher clamp force. So the fine pitch increases the clamp directly. And then by the fact of larger root diameter it can take even more torque.
larry

 

[SPYDERLK]

They also make heavy hex bolts and nuts that take larger wrenches than normal for the size. Helps spread holding pressure over a greater area for things like flanges on airlines or other pressure things

Hi strength heavy head bolts seem to have gotten pretty expensive of late. Flange head might be cheaper. Harder to get either in fine thread too.