Tools: calibrated torque wrench, screwdriver too?
I'm shopping for a quality, calibrated or calibratable torque wrench. I'm finding a price range from $200 (Aircraft Spruce) to $375 (Snap-On, 2% accuracy electronic). Stanley makes a really nice set of the "CX" series with a 3% accuracy. But I have no strong opinions. In the past, I just bought auto-grade torque wrenches and hoped for the best. Right now, I'm thinking 3/8" drive, 40-200 in-lbs Any recommendations from personal experience either angels or goats?
I have tapped, aluminum blocks to deal with along with the usual 4130 tubes attached via AN hardware. Now I like a ratchet wrench as much as the next guy but am I being a little paranoid about whether they can accurately measure the torque? I like the "memory" dial gauges but the electronic ones can be used "blind" and remember the max torque.
Also, does a torque screw driver make sense? I want to buy a quality tool but this is not going to be my livelyhood (although it might be important for my life.) Thoughts? Suggestions?
Thanks, Bob Wilson
Use the internet and check out CDI Torque. CDI Torque makes the Snapon Torque wrenches and is a Snapon owned company. With a little web surfing, you can find places where to procure CDI Torque wrenches at a discount.
Ratcheting types built by quality companies are fine. Just remember that anything in the bottom 10% and top 10% of full scale is most likely going to be pushing the error limits. For most people, they would be better off with two wrenches instead of one. A 1/4 drive 10-50 inch-pound fixed head and then a compact 3/8" 40-200 ratchet head. With the two, you have virtually everything covered on most light aircraft. With the small 1/4 drive, you can get it into very small places that would be difficult to swing a larger wrench. Also, with the fixed head, you are going to force yourself to learn to get the torque close by feel before you ever put the wrench on it. You would be suprized at how badly most people overtorque hardware. You generally don't need it to be gorilla tight.
At work, we have Stahwille handles with seperate heads for anything under 1000 inch-pounds. Over that and we have the big SnapOn 3/4" and 1" drive units for installing wings and pylons. The main thing is to take care of what ever you buy and if it gets dropped then it needs calibration.....
A quick little helper if you are torqueing for a cotter key or safety wire.... use a fine sharpie pen and draw a line on the head and the tip of the bolt to show the drilled hole. If you are working with edged drilled bolt heads, color the top of the head where the holes are. If you are using spline bolts, color the splines next to the holes. The lines or coloring makes it very easy to find the holes for alignment for the key or for safety wire in areas with limited visual access.
I don't know that there is a lot of value in having a torque screwdriver - most screws that need torqued aren't very tight, I just use a screwdriver socket with my regular torque wrench.
I don't care much for either the digital or dial type torque wrenches, I prefer the ones that you set & they click at the appropriate torque value.
Thank you! This is just what I needed.
I'm looking at the CGI tools and sent a question about calibrated models. Also, I like the idea of a 3/8" and 1/4" wrench and using a screw-driver adapter for those that need them. I also like the tip about marking safety wire holes on the face of the bolt head . . . that will save me a lot of grief.
Bob: Something that I forgot to add... If you buy ratcheting type wrenches, make sure you read the calibration/accuracy information that comes with it. There are some brands that have wrenches that meet the spec when going in only one direction. We got past that by having ones that were calibrated for both directions in our metrology lab. Those that didn't make the grade in both directions got color identifiers that let a user know if they had to watch direction when used. And there are times that I have had to run them backwards to torque fittings due to access.
Be sure to check the requirements for your prop bolts before you buy a torque wrench. Depending on your engine/prop combo it may not be sufficient to torque prop bolts, which can go as high as 70 foot pounds (840 inch pounds). I have a 1/4" drive torque wrench (clicking, ratcheting type) that goes up to 240 inch pounds and a 3/8" drive one that goes to 100 foot pounds.
Found a YouTube video on checking the accuracy of a torque wrench.
The majority of screws don't need to be torqued unless you are the type of person that tends to "screw" it up all the time (pun). The only time that I would worry about torquing screws is when it's going into something critical (engine block) or there are times when overtorquing might mess up the sealant you are using (in fuel tanks) or gaskets (like smashing out silicon valve cover gaskets). In most cases, just adapting your existing ratcheting torque wrench works fine.
I personally have the snap on electronic torque wrench and I love it! Because it is a strain gauge, it self calibrates at start up. So no worrying about getting it calibrated every year like you are supposed to with all other types. Simple and effective, it vibrates and beeps when you get to your torque then it tells you exactly what you torqued it to. Also, it does the conversions for you from InLb - FtLb. It's not that hard to do the math, but who WANTS to do math when you don't have to. I'm sure the CDI wrenches are j
As it has been said above, you really do need more then one wrench. Chances are you don't use them all very often, but when you need them you will have them. I personally need to get the next size up (1/2) probably up to 1000 inlbs
Also, just because they have a ratchet, doesn't mean you should actually ratchet with them. If you are just getting that last half turn and need to reset the wrench to hit your torque, fine. But if you are running down a 3 inch bolt with your torque wrench you are causing unnecessary wear.
Don't judge a torque wrench by its price. We won't buy Snap-on anymore at work due to them going out of calibration in about six months. Meanwhile I've taken my cheap $20 Harbor Freights in for calibration every year and they've been perfect at 2-3%. They do use standard parts so if there was a problem it could be fixed. There is nothing on a plane that would fail if your wrench was 5% out. I would consider a screwdriver if you are working on small fasteners like in magnetos.