Torque Question

[CarbideBob]

The correct amount of torque is bolt stretch.
Here is where anti-seize or oil come into play.
Dry some or rusty much torque is lost to friction, any type of lube changes this torque efficiency or loss under pressure.
On super critical stuff you measure the elongation or "bolt stretch".
I realize this not super fancy install but there can be a huge variation in dry and rusty vs new and lubed. Easy 40%.

 

[JIMMIEM]

I did several videos and posted them to Youtube about lubricants, clamping forces, torque applied, and stretching to the breaking point. It really was an eye opener, I would not have believed a lot of it. Go to YT and search for Fanta Machine Engine Studs in the titles.

Ed.

Thank You. I watched the video. Learned some new stuff. Never heard of ARP before.
Next question. Can you recommend a good thread pitch gauge tool....for both ASE and Metric.
Saw a bunch on Amazon, but didn't know which to get.
Thank You

 

[cg285]

there is probably a torque spec for a light switch. sigh

 

[WizardOfBoz]

I use anti-seize on just about every bolt I tighten that's not living in an oil bath. I drop 20% - 25% on torque vs dry rating. Lower end of that range for steel threads, a little more for aluminum threads.

Appreciate this info - very practical and clear how one would apply this paradigm. Thanks for the concise, clear explanation.

It would be interesting to test the strain of the bolt with/without antiseize and with/without the 20-25% reduction you mention.

 

[eKretz]

Appreciate this info - very practical and clear how one would apply this paradigm. Thanks for the concise, clear explanation.

It would be interesting to test the strain of the bolt with/without antiseize and with/without the 20-25% reduction you mention.

Looks like @atex57 did that already. An interesting addition to that test might be testing all the way to bolt failure and seeing how close to failure a bolt with anti-seize would be at rated dry torque without the reduction.

 

[atex57]

Looks like @atex57 did that already. An interesting addition to that test might be testing all the way to bolt failure and seeing how close to failure a bolt with anti-seize would be at rated dry torque without the reduction.

I thought about that but decided not to put my torque wrench to such an impulse load as a breaking stud. If you look at the later videos I actually tested to failure and had to catch the broken pieces with blocks of wood. Didn't do that at first and put a nifty dent in the shop refrigerator. Video 5 shows some very interesting results with depth of thread engagement and breaking strength.

Ed.

 

[JIMMIEM]

More than likely Loctite was used for liability reasons at the factory.
Are the bolts magnetic?


IMHO go to mc master and order alloy (whatever your pitch is?) use red Loctite and call it a day
If you ever need to change again, heat up and spin them out.

Thanks for the heads-up on McMaster-Carr. I placed an order. Good prices and next day delivery. The parts I ordered from the chipper manufacturer took 10 days to be delivered.

 

[JIMMIEM]

Grade 8.8 vs Grade 12.9 question.
The screws I ordered from McMaster-Carr are M10x50, thread pitch 1.5, zinc plated grade 12.9 alloy steel.
The screw that the chipper manufacturer sent to me was the same size but grade 8.8.
I can't find an on-line supplier that carries the grade 8.8 in the dimensions I need.
The chipper folks can't/won't tell me their screw manufacturer.
I will be using Loctite 263.
I have read that grade12.9 should not be used instead of the grade 8.8 due to brittleness.
One post said that the grade 12.9 could be used if only torqued to the grade 8.8 torque value.
I know I'm really overthinking this but do you think that it would be ok to use the grade 12.9 screws for my application?
Thank you.

 

[gbent]

All these questions and not once have you posted pictures of the actual usage of the bolt. Orientation matters. Usage matters. We are all shooting in the dark without the proper information.

But without knowing more specifics I would still be hesitant to use a 12.9 in an application with a cyclical load.

 

[Gordon Heaton]

. . .The chipper folks can't/won't tell me their screw manufacturer. . .

Probably because it's chinese junk. Often, decent-size chippers hold the blade captive in some sort of pocket, the bolts just keep it seated. If that's your situation it probably doesn't matter which of those two grades you use. This is why people are asking for photos. Too many variables. Keep in mind that metric grade 8.8 is approximately equivalent to our grade 5.

 

[technocrat]

The bolts are probably exposed to a shock load, equal torque is likely more important than hitting the correct torque in order to spread the load across the bolts.

 

[JIMMIEM]

All these questions and not once have you posted pictures of the actual usage of the bolt. Orientation matters. Usage matters. We are all shooting in the dark without the proper information.

But without knowing more specifics I would still be hesitant to use a 12.9 in an application with a cyclical load.

Here are some pictures. 3 Bolts are in 1 Bolt is not in yet. The last image of the Rotor Group is where I'm at.

 

[Gordon Heaton]

Not much support for the blades beyond what the bolts will provide. It appears to be a small, low hp chipper, correct? What's the shroud made of? I'm no engineer, but if it were me I'd bolt them in with what you've got and get to work. You can 'what if' yourself into doing nothing forever.

Seeing these pix it appears to be a hammer mill type. . .

It's a combo. There are two straight blades on the back plate, plus the hammer assembly.

 

[JIMMIEM]

Not much support for the blades beyond what the bolts will provide. It appears to be a small, low hp chipper, correct? What's the shroud made of? I'm no engineer, but if it were me I'd bolt them in with what you've got and get to work. You can 'what if' yourself into doing nothing forever.

Yes, a 7 hp machine. Maximum tree branch diameter is 3 inches. Shroud is metal. I don't know the gauge. OK, I'll use the grade 12.9 bolts. I tend to overthink/analyze.
Thank You for your time and patience.
The Y hammers (part # 4) rotate freely on the Spacers (part #3). The Rotor Assembly spins...the knives cut the tree branches and the Y hammers whip around and cut too.

 

[tdmidget]

Probably because it's chinese junk. Often, decent-size chippers hold the blade captive in some sort of pocket, the bolts just keep it seated. If that's your situation it probably doesn't matter which of those two grades you use. This is why people are asking for photos. Too many variables. Keep in mind that metric grade 8.8 is approximately equivalent to our grade 5.

Seeing these pix it appears to be a hammer mill type. The important thing is not to pinch the hammers so they do not swing freely. That explains the Lock tite requirement and no torque spec.

 

[JIMMIEM]

Seeing these pix it appears to be a hammer mill type. The important thing is not to pinch the hammers so they do not swing freely. That explains the Lock tite requirement and no torque spec.

On this machine the Y hammers do swing freely.

 

[gbent]

Are the bolts the axle for the hammer, or are they a retainer for a tubular axle?

 

[Bill D]

there is probably a torque spec for a light switch. sigh

Leviton 12-14 inch pounds, 20 for commercial devices
Hubbel 9-12 inch pounds
Bill D.

 

[JIMMIEM]

Are the bolts the axle for the hammer, or are they a retainer for a tubular axle?

The bolts are the retainer for the tubular axle. In the last schematic the tubular axle is part #3 which they call the Spacer. The Y hammer rotates freely on the Spacer. Part #5, Bearing Sleeve also fits over the tubular axle to position the Y hammer. I watched a Youtube video which made the schematic easier to understand.

 

[gbent]

Vastly different situation than standard screw loading. The screw is being loaded in shear, and the torque is to make sure it doesn't vibrate loose. Your 12.9 should be sufficient. I would install them with blue loctite in the hole, not on the screw threads. Reasonable torque, no value specified.