Sport Pilot Talk

I need a torque wrench, any recommendations? Mechanical vs digital? Brand? Also, what size 3/8’s and values? Mostly for oil changes and prop bolts.

FAR part 43 requires that torque wrenches be calibrated within the previous 12 calendar months. It costs something like $45 to get a torque wrench calibrated. Since I choose to use three different torque wrenches (1.4", 3/8", and 1/2" drives), that's $135 a year I have to budget to stay legal. But, when you buy a new torque wrench, it comes with a calibration sticker that covers you for the first year. So...

When Harbor Freight has its numerous sales throughout the year, it offers its torque wrenches for $9.95 each (with coupon). So, I can buy all three of them, new, for less than the cost of calibrating one used torque wrench. And,I'm then good for a full year (after which, there will be another Harbor Freight sale). These are pretty good click-type wrenches, which will certainly hold up to one year of continuous use (after which, they're going to get replaced anyway). So, why would I waste money on calibration, or on more expensive, fancy torque wrenches?

If you don't happen to subscribe to Harbor Freight sales coupons, you can find them in the monthly ads in AOPA Pilot, Sport Aviation, Flying Magazine, etc.

DISCLAIMER: I have NO commercial affiliation with Harbor Freight. Call me a satisfied customer.

BTW, what do you suppose I do with all my old torque wrenches? I give them away as door prizes at my numerous FAA WINGS safety seminars. I just have to be sure to mark them "Caution - this wrench is not calibrated. Not for use on aircraft."

drseti wrote:FAR part 43 requires that torque wrenches be calibrated within the previous 12 calendar months. It costs something like $45 to get a torque wrench calibrated. Since I choose to use three different torque wrenches (1.4", 3/8", and 1/2" drives), that's $135 a year I have to budget to stay legal. But, when you buy a new torque wrench, it comes with a calibration sticker that covers you for the first year. So...

When Harbor Freight has its numerous sales throughout the year, it offers its torque wrenches for $9.95 each (with coupon). So, I can buy all three of them, new, for less than the cost of calibrating one used torque wrench. And,I'm then good for a full year (after which, there will be another Harbor Freight sale). These are pretty good click-type wrenches, which will certainly hold up to one year of continuous use (after which, they're going to get replaced anyway). So, why would I waste money on calibration, or on more expensive, fancy torque wrenches?

If you don't happen to subscribe to Harbor Freight sales coupons, you can find them in the monthly ads in AOPA Pilot, Sport Aviation, Flying Magazine, etc.

DISCLAIMER: I have NO commercial affiliation with Harbor Freight. Call me a satisfied customer.

BTW, what do you suppose I do with all my old torque wrenches? I give them away as door prizes at my numerous FAA WINGS safety seminars. I just have to be sure to mark them "Caution - this wrench is not calibrated. Not for use on aircraft."

Thanks Paul, looks like I’ll be visiting HF this week.

I took the Professor’s advice some time ago and went the Harbor Freight route. 3/8” and 1/2”.

As cheap as they are, I’m a little paranoid. After setting them, I always clamp the drive end into a bench vise and take it to the click to make sure it feels right. With spark plugs, were the clicker to fail, one could do a lot of damage waiting for a click that never came.

That said, I’m on my third set and no problems to date.

That click test is a great idea, Eddie. I think I'll adopt it.

FastEddieB wrote:I took the Professor’s advice some time ago and went the Harbor Freight route. 3/8” and 1/2”.

As cheap as they are, I’m a little paranoid. After setting them, I always clamp the drive end into a bench vise and take it to the click to make sure it feels right. With spark plugs, were the clicker to fail, one could do a lot of damage waiting for a click that never came.

That said, I’m on my third set and no problems to date.

Just an observation, but with new NGK spark plugs I have found that they reach torque after 5/8 of a turn after the screwed in hand tight until the gasket seats. If the one time use gasket has already been compressed all bets are off.

Will 5-80 NM suffice? Is 3/8 drive sufficient for Rotax oil plug and plugs or do I need higher? I don’t have the maintenance manual handy.

I think you should have a 1/2” drive torque wrench as well.

Not sure about the ROTAX max specs offhand, but it may be handy for landing gear attach bolts and the like. Or, outside of aviation, for lug nuts and so forth.

As an aside, for tiny torques I also have a beam-style 1/4” drive designed for bicycles. It’s rarely called for, but handy occasionally.

As a further aside, there are times a socket is impractical. Then an open end or box end wrench and a spring scale can get the job done. If the force can be applied 12” out, no math involved - apply 50 lbs at 12” and you have 50 ft/lbs of torque. At different arms, some math is required*, and there are apps and websites to help with that.


*For instance, you can get 50 ft/lbs by applying 25 lbs at an arm of 24”. And so on.

Almost all of my work is done with a 3/8 in drive, except for avionics (which generally requires 1/4) and landing gear (which, as Eddie suggests, might need 1/2). The big outlier is the ccw nut which holds the drive gear onto the end of the crankshaft in a Rotax 912. If you have gearbox damage and have to replace the big reduction gear, the small drive gear gets changed with it (they're a matched set). That takes a 3/4 in drive monster socket, a crankshaft locking pin, a heat gun to get the old one off, and a whopping 150 ft lb of torque if memory serves. (But nobody should ever trust his or her memory for torquing anything! Look it up in the maintenance manual every time.)

drseti wrote:Almost all of my work is done with a 3/8 in drive, except for avionics (which generally requires 1/4) and landing gear (which, as Eddie suggests, might need 1/2). The big outlier is the ccw nut which holds the drive gear onto the end of the crankshaft in a Rotax 912. If you have gearbox damage and have to replace the big reduction gear, the small drive gear gets changed with it (they're a matched set). That takes a 3/4 in drive monster socket, a crankshaft locking pin, a heat gun to get the old one off, and a whopping 150 ft lb of torque if memory serves. (But nobody should ever trust his or her memory for torquing anything! Look it up in the maintenance manual every time.)

Funny you should mention this. Last month my mechanic and I had to pull off the gearbox for it's 600 hour service. He was afraid that getting that nut off might shear the locking pin. As it turned out it wasn't hard to get off at all(no heat gun required). It didn't look like there was any loctite. There is now and it's 125 ft/lbs. I'm sure when it's due for it's 1000 hour service it will be a bit more of a challenge to get off.

rcpilot wrote:It didn't look like there was any loctite.

Sounds like somebody didn't follow the maintenance manual last time. Glad you got the loctite on it this time.

I was also a bit afraid of shearing off the crankshaft locking pins, but it turns out if you torque them according to the spec, you put them under compression and they're actually stronger.

Geez, what are you doing with your "expired" torque wrenches? Send them to me :-/

The lowest a HF torque wrench will go is one of them claims 5lbs... most of the rest are 8lbs...

Setting the one I have for 8lbs seems too much for some of the small fine thread bolts I torque... just to the point of almost stripping them... and I've stripped a few that way. I accidentally stripped a headbolt on a motorcycle which was suppose to be 9 lbs...

What is a good cheap torque wrench with a lower limit for torquing ultralight AN bolts..?

choppergirl wrote:Geez, what are you doing with your "expired" torque wrenches? Send them to me :-/

I give them away as door prizes at my safety seminars - always emphasizing that they are not calibrated.

What is a good cheap torque wrench with a lower limit for torquing ultralight AN bolts..?

Harbor Freight 1/4 inch drive. On sale a couple of times a year for $9.95.

Some torque wrench observations:
-- Some "click-type" torque wrenches have a very subtle "click" so be sure you can feel/hear it.
-- Always unload or zero-out the wrench when you have finished using it for the day. And don't drop one!
-- Small "beam-type" wrenches made for bicycle use are very handy for small hardware and 1/4" sockets.
-- Become familiar with the various useful formulas that enable you to use extentions, crowsfoot, and other angles at the end of your wrench.
-- Don't use your torque wrench to initially break free a fastening -- use a ratchet or breaker bar.

RV12Heal wrote:Some torque wrench observations:
-- Always unload or zero-out the wrench when you have finished using it for the day. And don't drop one!

This is copied and pasted from Google, but I would suggest following the instructions that come with the wrench.

When a torque wrench is in regular use it does not need to be wound back. However, when storing a torque wrench for an extended period of time, users should always wind it down to the minimum scale setting and never to zero. ... Operate your torque wrench in a smooth and steady manner and remember that one click is enough