Measuring tension on tightening bolts?

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Old 11-05-14, 05:17 PM
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Measuring tension on tightening bolts?

Have two questions regarding the "torque" that is recommended by the EGO user manual when tightening a mower blade back into place, or, when replacing it. Here is the info:

Place a metal rod (e.g., a manual screwdriver) into the fixing hole to act as a stabilizer, then use a 9/16 inch (14mm) torque wrench (not included) to tighten the bolt clockwise. The recommended torque for the blade bolt is 36-43 ft-lb (49-59Nm) (Fig. 21).

Questions:

1) How do you measure the amount of torque you put on a bolt and what tool (or tools) can be used to measure it?

2) And, what does 36-43 ft-lb (49-59Nm) mean?
 

Last edited by homeowner888; 11-05-14 at 05:35 PM.
  #2  
Old 11-05-14, 05:41 PM
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1. A torque wrench is a tool designed to measure the torque when tightening nuts & bolts.

2. 36-43 is the acceptable range of torque for that fastener. Think of a wrench one foot long and 36-43 pounds hanging on the end pulling to tighten the fastener (one pound one foot from the pivot). The odd numbers are probably a result of the conversion from metric.

How critical is all this??? Probably not too serious for a mower blade. You want to tighten the bolt enough that it doesn't work loose and not so tight you can't remove it when needed.
 
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Old 11-05-14, 06:20 PM
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Torque wrench here is the firet one I got after googling it, there's pages of them.
Torque Wrenches: Buy Torque Wrenches in Hand Tools at Craftsman
And, what does 36-43 ft-lb (49-59Nm) mean?
Amount of pressure to put on wrench and will show on dial. here a video
https://www.youtube.com/watch?v=zgwwOJ0B964
 
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Old 11-06-14, 04:07 AM
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I've never used a torque wrench on a mower blade and have never had one come loose. Pretty much snug it up as tight as I can with a wrench without using an insane amount of pressure ..... but it doesn't hurt to own a torque wrench and it will help train you to get a feel on how tight to get the bolt.
 
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Old 11-06-14, 06:57 AM
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I Own two mowers and mow at least 6 lawns a week and have never once used a torque wrench to tighten a blade.
 
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Old 11-06-14, 12:44 PM
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Like the others I have never used a torque wrench to tighten a lawnmower blade. And I do own a nice torque wrench.
 
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Old 11-06-14, 02:29 PM
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Ditto on no torque wrench on blade, Just passed on info on torque wrench.
 
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Old 11-07-14, 06:32 PM
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Thanks for the replies as I have some other questions:

1) Is a craftsman 9/16 in. wrench with a 12-point closed end sufficient for the blade bolt on my EGO mower? Is it possible that a 12-point wrench could strip the bolt?

I just bought one from my local hardware store although someone else told me that the 12-point closed end could strip the bolt when I attempt to tighten up the blade bolt. I was told to buy one with a 6-point closed end, instead. When I went to the hardware store they only had a 12-point wrench so I bought it as they no longer carry the 6-point wrench!*

2) What is the difference between the two (i.e., 6-point, 12-point) and which one is better for tightening a blade bolt?

3) What wrenches do you recommend and use?

The EGO video below recommends a standard 9/16 in. wrench with a 6-point closed end to take off the bolt as they demonstrate it, here:

EGO Mower Blade Changing and Sharpening - YouTube

The Owner's Manual recommends a torque wrench to tighten it.

No one seems to agree upon using just ONE tool.

* Extra note:

Had to order the 9/16 in. wrench with 6-point closed end from amazon since my local store doesn't carry them any longer - bummer! They only sell 12-point wrenches.
 

Last edited by homeowner888; 11-07-14 at 09:08 PM.
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Old 11-07-14, 10:28 PM
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Manufacturers often go a little overboard in the instructions as a means to reduce liability. You are free to use a socket to both tighten and loosen the blade bolt-- the important thing is it Needs to be tight enough not to vibrate loose.
 
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Old 11-07-14, 10:32 PM
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Oh... and a 6- point wrench or socket is less likely to skip or round off the bolt head because it has more contact with the 6 sides of the head.
A 12- point can only grip the corners.
 
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Old 11-07-14, 11:26 PM
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Thanks for the info as the 6-point 9/16 in. wrench is on the way and although I probably won't need to change the mower blade this year (being at the end of the season) I will have one.

Also, has anyone made use of the beam torque wrench, below?

Name:  Craftsman Beam Torque Wrench.jpg
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I now own this and wonder if it will accurately torque the bolt to about 40 ft-lb as recommended in the EGO user manual - i.e., the middle of the 36 - 43 ft-lb range.

It has an odd pivot-style handle (feels weird and loose when picking it up) and I am trying to figure out exactly how to use it. I have no idea as to how one would apply torque and turn the bolt correctly and hopefully in the right direction?

Even the directions with the wrench don't tell you as to how to turn the bolt.
 
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Old 11-08-14, 01:34 AM
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The beam type of torque wrench you pictured is very common, easy to use and can be calibrated (more or less) by the user within a somewhat sloppy tolerance.

The pivot in the handle is so that no matter how you grip the handle the working length of the wrench, from the center of the socket to the pivot on the handle is the same. Otherwise the torque reading will be different with differences on how you hold the handle.

You only use the torque wrench for the final tightening, the last partial turn to bring it to the proper tightness. When you do so the indicator rod will remain stationary as the scale moves with the main wrench handle. Simply turn until the tip of the indicator coincides with the desired scale indication of torque.

How to Use a Torque Wrench - How to Tighten Lug Nuts - Popular Mechanics
 
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Old 11-08-14, 04:30 AM
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As I will have both tools (standard wrench & torque wrench) to remove and replace my mower blade the following questions still remain:

1) Do I trust my own instincts and use a standard wrench to tighten back the blade bolt to whatever I think is snug and tight (which is an estimation at best) or, use a torque wrench to tighten it to the proper specifications the manufacturer recommends?

2) Almost everyone here admits to manual tightening of blade bolts by tension perception so how do you know that you have applied precisely "40 ft-lb" - or, any other degree of torque just by feel alone?

It is now clear to me that a torque wrench should be used since there is no guesswork involved.
 

Last edited by homeowner888; 11-08-14 at 04:48 AM.
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Old 11-08-14, 05:25 AM
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The manufacture specifies a certain torque because they don't want to be responsible for someone not tightening the blade sufficiently. It doesn't really hurt to go tighter than spec'd but too tight will make it harder to remove, extreme over tightening could break something. Years of turning wrenches will give you a feel for how tight it is, not so much the torque setting but whether or not it's tight enough or too tight.

I don't think I have any 6 point wrenches but own a drawer full of 6 point sockets. I don't remember ever having any issues using a 12 point wrench on a mower blade but I am more apt to use a socket/ratchet.
 
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Old 11-08-14, 05:33 AM
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Turned wrenches for 40+ tears and go by feel for almost everything except very specified places (engine and wheel lugs) Wheel lugs from other peoples wheel offs.
 
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Old 11-08-14, 07:44 AM
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You are obviously concerned with safety here and wanting to follow manufacturers specs to the tee.

I highly recommend you return the beam-type wrench you purchased and buy a Micrometer/Click Type Torque Wrench.

The beam type takes too much work. You will have to tighten nut while looking directly at wrench gauge. This is hard to do with little experience.

The click type is expensive. But you can set it and forget it. Once you set torque value, you simply tighten nut until the wrench clicks, using one smooth motion.

Always set wrench back to zero after use.
 
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Old 11-08-14, 07:59 AM
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To get a feel for what the specified torque feels like, if you happen to have or have access to a vise, clamp a 3/8" bolt firmly in the vise, put a 9/16" socket on your torque wrench, and see how it feels at the desired torque. The torque wrench is longer than the wrench, making leverage a factor, but it will give you an idea of how much oomph you should apply to the wrench.
 
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Old 11-08-14, 08:25 AM
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You can get a decent clicker style from Grizzly or one of the other discount places. Sure, they may not be NASCAR grade, but for basic tasks like lugs and mower blades, they'll work fine.
 
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Old 11-09-14, 07:08 AM
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Fairly low-priced nowadays, although the low-end models are probably not necessarily as accurate for exacting tolerances like you would need in the aerospace industry. They would certainly be accurate enough for a lawn mower blade:

Amazon.com: torque wrench: Automotive

Tech tip from a retired military aircraft maintainer: When using a "click-type" torque wrench ALWAYS return the torque setting on the wrench to "0" between uses.

 
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Old 11-09-14, 07:13 AM
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Always set wrench back to zero after use.
Can't be over emphasized! I had a clicker type torque wrench for years that worked well but I didn't know to set it back to zero when done It sat in the tool box unused for a year or two and then wouldn't work when I needed it. While not as handy, my beam torque wrench has been trouble free for decades
 
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Old 11-10-14, 09:52 AM
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There is another type clicker torque wrench that I like and own called a "split-beam" torque wrench. They cost a little more than one from Sears or Harbor Freight but they have the advantage of never needing to return the setting to zero when done. There's no spring in them to weaken over time.

Amazon
 
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Old 11-16-14, 04:22 PM
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@marksr,

Looks like I will be using a $25 beam torque wrench I found at my local hardware place and it's good to know they are trouble free and should do the job as necessary. It is snowing here now and will have 2 to 3 inches by morning so it appears there won't be any more mowing this year. Will be making some "mud" on a cold day!
 
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Old 11-30-14, 02:13 PM
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Unless you turn your mower upside down you'll need to read your torque wrench via a mirror.
 
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Old 12-01-14, 03:25 AM
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Congrats on getting a torque wrench.
Having a lot of experience with manually tightening fasteners often means you have experience breaking bolts or having them uneven or loose.
You are going to skip that process.

After you have used it for awhile you will have a feeling for how tight things should be.
When you torque a fastener you can test the "feel" with a normal length wrench to see what manually tightening feels like.

If you gain confidence hand tightening you can reserve the t wrench for critical fasteners like head bolts and wheel lug nuts.
 
 

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