[Adam Oke]

I'm in the market for a decent torque wrench for my build. I just need a wrench to get me through the tail/wings/fuse for now. I can pick up another wrench and/or borrow for the engine/prop. As far as I can figure, it should be a 1/4" and in the 20-150 inch pound range. Most of my tools that I use often are Sioux, Klein, Snap-On, Mastercraft etc, so I'm not afraid of buying quality on the tools I use often. With the amount of times I will use it, is it necessary to spend the big bucks on a good torque wrench? Is a wrench from Princess Auto being too cheap in this area? I can also make a run over the boarder and pick up a Harbor Freight wrench as well. The common mid-range wrench that I read around here, appears to be the CDI Wrenches, which are a Snap-On brand.

The more I get reading, the more I wonder if +/-1 to 4% is really necessary. I am building an airplane, not a watch.

Here are some suggested torque values:
AN3 20 to 25 Inch Pounds -- Average 23 = -15/+9% Average Torque Value Tolerance
AN4 50 to 70 Inch Pounds -- Average 60 = -20/+16% Average Torque Value Tolerance
AN5 100 to 140 Inch Pounds -- Average 120 = -20/+16% Average Torque Value Tolerance
AN6 160 to 190 Inch Pounds -- Average 175 = -9/+8% Average Torque Value Tolerance
AN7 450 to 500 Inch Pounds -- Average 475 = -5/+5% Average Torque Value Tolerance
AN8 480 to 690 Inch Pounds -- Average 585 = -22/+18% Average Torque Value Tolerance
AN9 800 to 1000 Inch Pounds -- Average 900 = -13/+11% Average Torque Value Tolerance
AN10 1100 to 1300 Inch Pounds -- Average 1200 = -9/+8% Average Torque Value Tolerance
AN12 2300 to 2500 Inch Pounds -- Average 2400 = -4/+4% Average Torque Value Tolerance

The average torque value tolerances are roughly calculated and rounded. I haven't read too much into the plans beyond the tail, but my understanding is the majority of bolts on this project (tail, wings, fuse) are AN3 and AN4. These have quite a tolerance range. I am wondering if it is really neccessary to buy a wrench that is +/-1% when the tolerance range is about +/-15% for most of the work!

Obviously on critical parts (ie Prop) I will use/rent/borrow an accurate, high end, calibrated wrench. For these parts with such a large range of tolerances, I am starting to think that the Princess Auto torque wrench will suffice. Even if it seizes up, it has a lifetime warranty and I can go swap it for a new one. Heck, if I want to "re-calibrate" every so often -- I can swap it for a new one!

What kind of click-type 1/4" wrench in the 20-150 inch pound range do you suggest?

 

[Rupester]

So you know...

I bought a 0-75 in-lb torque wrench intended for - and sold by - bicycle repair shops. It was w-a-y less costly than a fancy one. I'm totally happy with it.

And yes, you'll rarely encounter machine screws in an RV that aren't AN3 or AN4, hence the smaller in-lb wrenches are far more useful.

 

[krwalsh]

eBay and Sturtevant Torque Wrenches

eBay will find you numerous beam-style Sturtevant torque wrenches. I think I got both of mine for $50 plus shipping. Try to get one that isn;t so rusted and doesn't have any significant scratches on the beam.

Since the beam type have no moving parts, there really is nothing to wear out. Both of mine are older than I am, and they work perfectly fine. Yes, you actually have to read the scale as you torque it, and not just wait for a satisfying "click" but from various sources the clickers are generally less accurate. They are certainly subject to whether or not you unload them after each use.

 

[az_gila]

.....
The more I get reading, the more I wonder if +/-1 to 4% is really necessary. I am building an airplane, not a watch.
....

I think the 1% torque renches are going to be many $$$

This is the spec from Snap-On for their $250 range click wrenches

http://buy1.snapon.com/catalog/item..._ID=640949&group_ID=675226&store=&dir=catalog

Note -

All QD Series Torque Instruments are accurate to ?4% clockwise and ?6% counterclockwise from 20% of full scale to full scale.

The beam ones probably don't drift over time, but who konws what the initial accuracy is? Park Tools does not give a number...

 

[Mike S]

I used a Snap On QC2175 to do my prop bolts, as it is designed to be used with an inline open end head, or other interchangeable heads, including a ratchet.

For most everything else, I used a Snap On 3/8" drive in/lb unit.

Both are click type, not beam.

 

[frankh]

Take the cheapest inch pound wrench you can find (harbor freight).. Use this get get a hand feel of how tight your AN3 botls should be. according to the book values. You will ba amazed at how little torque this actually is.

Put a bolt in a vise and keep adding torque until you feel the thread streatch (or it breaks).. Take a point roughly between th two reading above and replicate that by hand.

You can do this easily without a torque wrench.

The idea that a bolt will break if it has too much torque is nonsense..Unless you have torqued the thread beyond the yield point..By which time it is on the verge of breaking anyway.

You'll save a lot of time needlessly torquing bolts this way.

 

[N941WR]

Every time I look at this wrench, the price seems to go up. Still, I'm happy I have it.


(Click image for details)

Don't forget to get some torque seal. A bolt that is not marked, is not torqued.

I have a beam style wrench for the big stuff but wish I had a click style.