Torque down a cylinder

chillydog · December 02, 2013, 11:22:09 PM

I've put together cheap homeowner saws with good ol' seat of the pants torquing of the cylinder to a good firm, solid "that oughta do ya", but I have a couple of nicer Stihls that I'd like numbers on. How much torque is needed for the jugs on a 026 and a 036?

Andyshine77 · December 03, 2013, 12:23:07 AM

7.7ft lb on the 026 and 8.5 on the 036 I normally snug them down good "AKA that oughta do ya", heat cycle the engine and check them after it cools down.

motard · December 03, 2013, 08:19:19 AM

I been turning bolts so long my wrist just clicks when it's just right!

NCFarmboy · December 03, 2013, 08:34:08 AM

I've been turning wrenches for over 50 yr's. My mentor would come back from the grave and whup (whup is worse than whip) my behind if I didn't use a torque wrench. I always torque my cyl screws and base screws on clam shell motors. I know a lot of guys go by thats tight enough just not me. Too many years as professional mechanic.
Shep

submarinesailor · December 03, 2013, 12:59:34 PM

I agree with that "NC Farmboy". After the work I did in the Navy, I would NEVER put something like a saw together with a torgue wrench. And thats a GOOD one, not a cheap one.

Bruce

JohnG28 · December 03, 2013, 02:29:01 PM

Quote from: submarinesailor on December 03, 2013, 12:59:34 PM
I agree with that "NC Farmboy". After the work I did in the Navy, I would NEVER put something like a saw together without a torgue wrench. And thats a GOOD one, not a cheap one.

Bruce

Fixed that for you.

Andyshine77 · December 03, 2013, 03:33:42 PM

Quote from: submarinesailor on December 03, 2013, 12:59:34 PM
I agree with that "NC Farmboy". After the work I did in the Navy, I would NEVER put something like a saw together with a torgue wrench. And thats a GOOD one, not a cheap one.

Bruce

I get what you're saying, it's simply not necessary, but at the same time it doesn't hurt a thing to use a torque wrench, so buy all means have at it.

clww · December 03, 2013, 08:43:17 PM

After the work I did in the Navy, using a torque is NOT an option, only a NECESSITY. ;)

Al_Smith · December 03, 2013, 09:05:55 PM

Part of my job concerns threaded fasteners used on automotive engines and the setting and calibrations of the automatic and semi automatic machines that do the tightening .

Statement : A properly torqued fastener will almost never fail if the design criteria is correct as a far as buried threads to engage .An under torqued fastener is certain to fail given enough time.

As far as torque wrenchs I have both a Snap-On dial type 1/4" in inch pounds and a Wiha break away beam in Newton Meters .

Yeah I'm part of that fraternity of underwater sea dogs too .Somethings stick forever I guess . ;)

NCFarmboy · December 04, 2013, 08:46:46 AM

Quote from: Al_Smith on December 03, 2013, 09:05:55 PM
Part of my job concerns threaded fasteners used on automotive engines and the setting and calibrations of the automatic and semi automatic machines that do the tightening .

Statement : A properly torqued fastener will almost never fail if the design criteria is correct as a far as buried threads to engage .An under torqued fastener is certain to fail given enough time.

As far as torque wrenchs I have both a Snap-On dial type 1/4" in inch pounds and a Wiha break away beam in Newton Meters .

Yeah I'm part of that fraternity of underwater sea dogs too .Somethings stick forever I guess . ;)

Snapon 3/8" dial type in in # & nm is what I use for saws. Old sea dog myself. Ship I was on had 4' torque wrench for cyl bolts on Detroit 268A IIRC. Torque was 750 ft #. I used to do em with no cheater but I was 20 yrs old too. ;D
Shep

motard · December 04, 2013, 11:38:02 AM

Torque wrenches are good.

Torque multipliers when you need to get serious.

shootingarts · December 05, 2013, 04:32:17 PM

Al mentioned undertorquing issues, a fine time to point out that too much torque causes a lot of grief too. A friend couldn't keep head gaskets on his race car. He had started off with the "if a little is good a lot is better" theory and as head gaskets failed he just kept tightening the head bolts tighter and tighter with less success all the time!

I finally got him to buy a new set of quality bolts and tighten them down to factory spec's. No more blown head gaskets. Even if an over tightened bolt doesn't break it can still exceed it's fail load and stretch like a rubber band! Clean threads, lightly lubed or apply your favorite snot, torque on the numbers.

When both ends of a fastener can be reached like a rod cap bolt on a car sometimes stretch is measured instead of torque. Stretch more accurately measures that each individual bolt is properly tensioned.

Seven to nine footpounds isn't much. I would bet most cylinders cranked down by feel are overtightened.

Hu

SPIKER · December 05, 2013, 08:18:46 PM

I'm EX Air Force so in the use a torque wrench camp for sure. On the Light Torque fasteners it is harder to gauge proper torque and damage gaskets than the 150 ft lb ones. On my first evaluation for Hydraulics Tech I was installing some hyd actuator jack screw or something forget now. I actually failed because they said I had over torqued the AN fitting! >:( The guy was standing back about 5 or 6 feet behind me and when tightening it up with the torque wrench I hit the handle end against a different hard Line and it "CLICKED" noise NOT the head of the unit clicking for proper torque. I ratcheted it up and was taking some more and he stopped me, YOU FAIL !!

>:( :

Well I tried to explain what happened but the guy was a royal P.I.T.A. Anyhow he would not have it and failed me for my evaluation. Guess what when HE signed off on the fitting and they test rant it it spewed oil like crazy. 8) 8) :D ;D Needless to say when they asked me WHY it was leaking I had to tell them! ;) HE was written up for not listening to the Technician who had high competency at his job

The crew chief wrote up that other SSGT for failing to properly preform checks or even follow up on what I had said. Luckily for me it was all documented in the aircraft forms. (BTW it took almost a full turn to get to proper torque on that line he failed me on...)

Mark

Al_Smith · December 05, 2013, 08:41:12 PM

You can get really into the science of it if you want to .Standad SAE methods depending on grade ,size ,threads per inch etc .You take the fastener to yield then a certain amount of degrees past depending .Yield is a point of the torque rising liniar in relation to the degrees of rotation .If it fails to rise you have exceeded the fasteners strength and either the fastener is failing or you are pulling threads .

That's hocus pocus on machine tightening and is seldom used by the average mechanic .

FWIW improper fastening methods are the leading cause of recalls on automotive products which is why the auto industry is so keen on it .I'm right there in the trenchs I deal with it every day .

Al_Smith · December 05, 2013, 08:57:25 PM

Let me ramble on a little longer--facts:
By definition in physics a screw as we know it is an inclined plane around the circumference of a cylinder .SAE threads are given in threads per inch .Metric threads are by thread spacing such as M14 1.25 which is world wide standard for most spark plugs .

By simple assimulation a screw acts like a spring under tension .Under tensioned it won't hold .Over tensioned it exceeds its' elastic strength just like a hyper-extended spring .Screws 101 not to be confused with junk yard dawg 101 . ;D

shootingarts · December 05, 2013, 11:16:51 PM

Quote from: Al_Smith on December 05, 2013, 08:41:12 PM
You can get really into the science of it if you want to .Standad SAE methods depending on grade ,size ,threads per inch etc .You take the fastener to yield then a certain amount of degrees past depending .Yield is a point of the torque rising liniar in relation to the degrees of rotation .If it fails to rise you have exceeded the fasteners strength and either the fastener is failing or you are pulling threads .

That's hocus pocus on machine tightening and is seldom used by the average mechanic .

FWIW improper fastening methods are the leading cause of recalls on automotive products which is why the auto industry is so keen on it .I'm right there in the trenchs I deal with it every day .

Al,

A quick question to satisfy idle curiosity and then I'll let the thread get back to it's regular program. On things like head bolts and main bearing bolts do they still use the machine that torques down every bolt in the set at the same time and holds torque pressure for a set time or until manually released? I know these beasts were in use long ago but I don't know if they still go to that expense for every engine.

Hu

Al_Smith · December 06, 2013, 06:42:33 AM

Head bolts are sequencialy ran down in steps .

Rod bolts are ran down one rod at a time with a torgue to turn rotational test .The mains are also done somewhat that way .Not one fastener on the entire engine is hand tightened .

Al_Smith · December 06, 2013, 06:58:50 AM

More on that .That every bolt at one time deal on machine tighening is the old FEC method .FEC is "first electric company" .Very reliable but "old school" .

Now of days it's done with basicaly servo motors and computors .Rocket science for a bolt more or less . Righty tighty,lefty loosey .Tight is tight ,too tight is broke . ;D