Is degree torqueing more accurate? Im old school and have always click torqued my bolts, but it seems more and more Im running into the degree torqueing. I know its been around for awhile but in my mind I just don't see that degree torqueing is that accurate. Can someone explain this in a fashion that makes sense to me? When Ive done degree torqueing it seems to be all over the place. I still think click torqueing is more accurate.
My opinion is that degree torque is more accurate because it eliminates the variables that affect the click type. The condition of threads on bolt and hole and how much lubrication on threads and shoulder of bolt mainly. When you torque by degrees it stretches each bolt the same no matter what. The main thing I like is torqueing big bolts with an impact and some marks on the socket!
What things are you guys torquing that specify angles? I have only run into that on head bolts. And I was always taught that head bolts that angle torque are generally one-time-use.
Rods and mains on a 3406 cat most recently, it seems like Cummins head bolts, some stuff for the variable valve actuators in certain C-15 cats. Those bolts get reused, I know Chevy head bolts that are torqued by degree are one time use.
The clicker type of torque wrenches I have and have used depend on what is basically a detent with variable spring tension on the detent ball. It is only as accurate as the strength and durability of the spring and the durability of the notch the ball is pushing against. I've had to have the guts of my 600 pound wrench replaced several times over the years. What I was schooled by a bolt salesman who was also an engineer was that the high stress applications pull the bolts into what is called yield. Basically the bolt is pulled until it stretches to the point of not coming back to the same length as it was originally. That is why Cummins give you a bolt gauge when you replace the head gaskets on one of those engines. The initial torque you put on the bolts provides a starting point and the extra turn provides a mathematically calculated amount of bolt stretch and ensures the bolt is pulled to its yield point. Another point I got from a master chief when I was in the Navy was that the click type torque wrench is the least accurate method of torquing a bolt for the reasons I stated above. His statement all the years ago was that the deflecting beam type torque wrench was the most accurate because temperature and your line of sight were the only things affect its accuracy. Someone might correct me but I have been told that click type torque wrenches are not supposed to be used on aircraft. Maybe someone here can confirm or deny that.
At the college where I took mechanic courses they had the calibrated weight type torque wrench testers on the wall across from the tool crib. You got a clicker torque wrench, you calibrated it on the wall to whatever you wanted and you walked back to the shop and used it. They would yell at you if you started dialing it up while looking at the micrometer handle, they said we don't calibrate those things, use the tester!
John C is bang on. These days more fasteners are taken close to their elastic limit. Where years ago it was generally only cylinder head bolts now it's all sorts of fasteners. Torque-turn fasteners are single-use UNLESS the shop manual specifically says othewrwise. The way I see it is that torque + turn is a more accurate way of obtaining a specific bolt loading. Remember that for any bolted joint the tension, bolt loading, call it what you will, is directly proportional to the TPI of the bolt and therefore the number of turns you put on the bolt after app the parts are in contact with one another is directly proportional to the load on the bolt. What really messes everything up is friction. Friction + load is what causes a click-type torque wrench to cllick, that's why you have to be really careful when using any type of lubricant, anything from oil to anti-seize, unless the manual procedure specifically calls for it. I have a story about a 789 front stub axle that sheared brand-new bolts when someone used moly-based anti-seize that wasn't called for in the D&A procedure then pulled the bolts up to the torque specified in the manual. The procedure called for a "thin coating of light oil" on the bolts before installation. So the basic idea of torque-turn is to apply a low torque that is just enough to pull the mating parts together and not enough for friction to rear its ugle head, then apply a known load to the bolt by turning it X degrees.
Only ones I can think of off-hand are the axles on Cat skid steer loaders. The 8 nuts holding the axle assembly to the frame needed to be torqued with the torque and turn method.
Track master bolts and sprocket segment bolts on Cat equipment
I don't think the little text window is big enough to list all the different components I've come across on Cat equipment that are torque-turn ........ I looked at one model that we have in our current fleet and there are 31 different sets of fasteners that are torque-turn. On another model - 23.
I wish manufacturers would spec torque values using anti-seize instead of light oil like you mention. I think it would make a big difference on the equipment that sees less than 1000 hours a year where it takes years before most things have to taken apart.
Torquing bolts in most cases is a ball park at best. The issue is turning a fastener tight enough so that it doesn't come loose. A torque wrench then is only a way to ensure the bolt gets turned to the minimum needed to not come loose. The torque turn methods are used where bolt tensile strength is engineered to go to the maximum extent. Cummins B and C series engines are an example. They needed to torque turn the bolts because they had to use smaller bolts to get the size of the engines down to fit in small equipment. They could easily have gone to the next larger size bolt and not had to torque turn it to hold the head down. But then again they would have needed to make the head and block physically larger to make up for the space the larger bolts take up. All this is to take the stresses that are at a maximum. Ask someone who has reused Cummins B series engine con rod bolts. They are to be used only once for a reason. They like making holes in blocks the second time they are used. First time I tore down one of those motors it looked to me like the rod bolts were smaller than those used on a 327 Chevy V8. The issue of anti seize compound for me concerns fasteners that are subject to environment issues. Bottom rollers, manifold bolts, accessory mountings and drives, sheet metal, mounting flanges for covers and linkages and on and on are where anti seize is appropriate. Things like component mounting bolts with blind holes or that open to oil sumps aren't that critical. Then again those types of items usually aren't specified to use a torque turn.
There's no reason why anti-seize can't be used with a torque setting when the manual doesn't call for it. All that has to be done is to reduce the torque value by a certain % depending on the type of anti-seize used. I have a table somewhere giving the numbers for all the different types. I don't recall all of them but I do remember that for moly-based anti-seize it's 45%, so my story of the sheared bolts in post #7 above makes sense because the guys didn't reduce the torque setting below what was in the manual when they pulled up the bolts.
I didn't know that was something that could be accounted for. I do wish more stuff was assembled from the factory with anti-seize though.
Lots of questions here and some good information. Click wrenches are not as accurate and not recommended for aircraft? The Snap On clickers I purchased in the eighties still test OK on the tool truck machine. They have been recalibrated a few times. Problem? Some airplanes have some left handed threads and my clickers do not torque left handed. So no not recommended. The new guy has a Snap On wrench which will torque by Ft. Lbs. Nm. and degrees. It is great. Torque everything to spec and double check. Then set to the degrees you want. 90, 120, 180 etc. It does not care if you are right side up, upside down or where the sun and the moon are. If you run out of travel you can rachet back and carry on. Nap time catch ya on the flip flop.
At the college, they had hung another tester crooked on the wall so the pointer hung straight down on the maximum reading. Somebody had made an arc shaped piece of steel and stamped torque readings into it backwards so that became the left handed torque tester. It was ugly but it worked. Not that I can remember torquing anything in reverse there. I suppose old pickup lug nuts but I didn't have any.
Would I be dating myself if I mentioned the 1/2 inch left hand bolt that locked the countershaft clutch brake in the front of a Mack Quadra-plex transmission?
Yea.... Pretty much LOL
I don't recall that. When you have one of those monstars on a jack and a wheel breaks through the 3/4 inch plywood the fun has just begun. I remember that. JD 320 skid steer head, 4240 rods, and tons of Cat stuff.
The digital torque wrench that will do degrees has a row of lights and an alarm when the degree is reached. It also displays Ft Lbs at the same time. In the 200 Ft Lb range it is not uncommon to see a 20 Lb difference between bolts. Yes torque turn is more accurate. Thanks for the info on different torques with anti seize. I have been lucky.
I believe there are different torque specs for plated vs non-plated fastners as well.
I like the old beam type torque wrench with smaller values . http://www.sears.com/craftsman-3-8-...MIyf3p_Nyf2wIVirxkCh06YA3MEAAYASAAEgLW0vD_BwE On heavy torque pounds I go by what it took to break it loose . Pull the same hard when going back together .
While not mechanical as such, an electrical fire I was called out to rebuild, came to a lawsuit. I was subpoenaed as an "expert witness." (what a laugh.) One of the questions that came up, outside of my "expertise," was the torque of the switchgear. It came down to the fact that more than likely everything had been over torqued. Over torquing as other have pointed out stretches the bolts, when the copper bus gets a heavy electrical load on it, it expands as do all metals. (I think.) Anyway , over torquing the bolts allowed everything to stretch, then come loose and then over heat because of resistance due to poor connection. End result, a 3.5 million dollar fire that the original electrical contractor was on the hook for. My part was quite infinitesimal, but sitting there was very educational. 40 years ago, proper torque was "as tight as you could get 'er plus an additional nudge." With the new CAD equipment, everything is right on the nubbins with very little "over build." Torque now is so much more important because of cheaper manufacturing in buildings and associated equipment.
Alll low, medium, & high voltage connections will loosen over time due to the fact the electrical supply is AC rather than the actual load in amps on the switchgear. Part of the PM system on HV switchgear is to tighten all the hardware at least twice a year. My #2 & #3 sons both work in the electrical supply industry. The voltage applied will vary from zero to circuit voltage, back to zero, then to negative circuit voltage and back to zero 60 times a second. Pull any electrical connector apart that has been used on an AC supply and you'll find the hardware will tighten. Tighten it and look at it again in 12 months time and it will again be less than tight rather than plain "loose".
This might be the reason the power company was not happy when the saw that the contractor who did some work on my house a few years back used connectors with set screws in stead of crimp connector at the main power feed lines to the house.
According to #2 son who was here to visit a few minutes ago, the latest UK Electrical Regulations (Part P, 17th Edition) call for all connectors on domestic installations that use screwed hardware have to be checked and re-tightened every 2 years. Remember that's on 230V 50-cycle AC, not 110V.
All that is interesting. Is there any different torque recommendations for bolts with loctite applied?
I was taught as a aircraft mechanic that the dial was more accurate.
Dial not beam! They still do not do degrees.
Not AFAIK. The idea was to stop fasteners coming loose through vibration. Applying Loctite to a bolt indicates that no other product (e.g. oil or anti-seize) would be used at the same time, therefore you stick with the specified torque for the bolt. If Loctite was considered to be some form of lubricant then a case could be made for reducing the torque on a fastener if Loctite was used where the specified torque was on a dry bolt. I've hever heard of this though.
I threw all the clicker torque's away years ago, to me dial torque wrenches seem to be far more accurate and stay accurate better than any clicker torque wrench. I like the degree torques on bolts, never had an issue on any I've ever used degree torques on.
I've never had an issue with any of the types. In the past I had enough feel in my hands to know when a wrench was weak and needed attention. For the most part anymore I pull things snug and do my own turn on the not so critical stuff anyway.
Or enough feel & experience where ya pull according to the bolt size like on rods , main bearing caps & heads . It don't work everywhere ..... Some applications will use a big bolt with low torque value . The 6-71 on the Ford uses 7/16 inch bolts that get pulled down to 20 foot pounds . Any other time we would yank a 7/16 bolt to 55 pounds .
The clicker torques won't click is the issue I've had with them, on certain airplane parts, which are aluminum to start with and small bolts, some are torqued to 15 ft/lbs and have to be precise, we've over torqued them and ruined and stripped threads out by over torquing by even a few pounds. I've also twisted off head bolts that were torqued to yield with clicker torques before due to the clicker not working and being precise enough. For years we used dial torques as a standard to set the clickers to before doing precise work, just to double check the clicker torques, finally we just threw away the clicker torques and use only the dial torques. On small parts and low torque values one person can use a dial torque, on larger bolts and higher torques it takes two people, one to do the pulling and a second to read the dial. On the clicker torques, you can have them calibrated before you torque to yield head bolts and before your done with all the bolts on the same head, the clicker can be off by a wide margin and you end up over torquing or under torquing bolts. If you can "feel" a certain torque, lucky for you, personally I can't tell if I'm torquing a bolt to 28 ft lbs or actually torquing it to 38 ft lbs, but in aluminum castings and special bolts, the 10 lbs extra can mean stripped out threads in a hole. When we're doing higher torques, say over 200 ft.lbs or even much higher still, and depending on how long the day has been, I might be off by a whole lot depending on where your standing, what your standing on and how many interruptions we've had on the same project from start to finish and how many of them we've done before. When we get into those 500 plus ft lbs torque, again depending on how many bolts need torquing in the same day, I'd rather have a dial torque to read, just to be sure. The same goes for taking things apart, I have one son who's strong as an ox, so when he goes by "feel" and depending on if he used lock tight, anti seize, or oil on the bolts or nuts, can mean me being able to even get the stuff back apart at all, more than once I've had to load a machine up, drag it home, put it in the shop, to get near the shop air and a really big impact to get the fricken part off he's put on. Don't even start on lug nuts on semi's and trucks, I can't begin to count the times I've had a flat and someone's used the impact to rattle those fricken things on to the point not even an inch impact can get them off with heat applied besides and you end up twisting off the bolts to get the rim off, and those times its usually on a weekend, your out of cell service and its either raining or snowing or dark, or all the above and your usually late to either get the wide load off the road or about as far from home as you can physically get. So around my place, if you rattle nuts on to the point the impact can't possible give it any more, instead of using a torque wrench to do the final torquing, your also the same person who's going to go get them back off again, no matter the time of day or day of the week, weeks, months or years later when the rims need to come back off. Also when it comes to rims and tires on trucks, if you "don't" use anti seize on things as you put it back together, your the one who's going to try to figure out how to get those dayton rims off the hub, and if you twist off the bolts, your also the one who's going to pull the drums and hubs off to replace those bolts as well, no matter what the book says to install them dry and without anti seize.
I know everyone says install lug nuts on trucks dry, but in the quarry I always used the anti-seize on them. 98% of the ten-wheelers we had used the cast spoke Dayton type wheels and between the stone dust and the muddy roads from watering the roads down to control dust running the lug nuts dry would almost guarantee you would have major problems when it came time to remove one. I always used one of those clicker type torque wrenches, a good Snap-On one. Now it may not have seen the constant use of say a wrench in a big fleet so it seemed to work just fine. I made it a point to recheck the torques on lug nuts within a day or two of replacing a wheel and most of the time only one or two would turn any amount. Before I was doing almost every tire change it was very common to have wheels slip and damage valve stems or other problems. Back then it was common for other people to just hammer the lug nuts on with a 3/4 inch impact and call that good enough. Most important thing I felt was to have all the components clean of mud and rust scale then I preferred to use a 1/2 inch impact to tighten up and spin the wheel to make sure it was running true and then go to the torque wrench. Another thing I did that may not be considered right by some was to use SAE flat washers under the nuts on all the wheel wedges and I replaced them with new if the old ones were worn or distorted. Now one also has to understand that the trucks I was dealing with probably never saw 25 mph empty or loaded but were loaded to the max a loader operator could fit in the box and ran on rough and uneven roads all the time. If working on trucks running 80 mph on Interstate highways doing 150,000 miles or more a year that might call for a different plan of attack!
After awhile pullin wrenches a feller can look at the bolt size & application and know how hard to pull on it . It takes a little time . Ya just know when it's tight ....
I have an apprentice and he is big and strong and it is hard to get this across that some small bolts just don't need to be that tight. I think I need to start packing a torque wrench so he can learn the correct feel for the sizes of fasteners.
Worked the same on the road equipment but never used flat washers. Problem came from going behind a moron with a big air gun, messing up studs, mixing up wedges, crushing spacers and such.
I like deg. specs; A paint marker and impact is so much easier on my back. I hate to admit it but the old school guys are right that if you know your tools you can get within 5% with feel.
In some applications, specifically JD 6068 head bolts, on the final torque turn you can feel the bolt give and it almost feels like a torsional spring. In attempt to convince my helper I could feel when the bolt reached it's correct yeild I had him mark the bolts with a paint pin and go ahead and place the pull handle on the bolt , each time I was with in 5% .
Great point partsandservice ! You can tell when the hardware is nearing it's limits . Bolt / stud is stretching or threads are pulling out .