torque wrench inadequecy??

[Ferd/289]

I need to torque a crankshaft bolt to 180 Ft. Lbs. I have two torque wrenches that only go to 150 ft. lbs. Do I need to get a larger torque wrench? Any tricks to use the ones I have.

Ferd

[Dragonfly]

Torque = force X length. With that if you were to increase the effective length of your torque wrench you could achieve the torque you want. Since I don't know how long the effective length of your wrench is I can only guess but you will need to add aproxamately 1 1/4" in length to the wrench. The easiest way to do that is to get an offset crows foot but that would be very difficult to use on the crankshaft bolt.

 

Probably the best thing to do would be to go to a parts store and ask them if they have a tool loaner program then borrow a 200 ft/lb torque wrench to do the job.

 

Dragonfly

[Pop N Wood]

Yeah, borrow a bigger wrench from Autozone or rent one from a rental place.

 

Or just buy one for your self and consider it an investment in your tool future.

[TimZ]

Torque = force X length. With that if you were to increase the effective length of your torque wrench you could achieve the torque you want. Since I don't know how long the effective length of your wrench is I can only guess but you will need to add aproxamately 1 1/4" in length to the wrench. The easiest way to do that is to get an offset crows foot but that would be very difficult to use on the crankshaft bolt.

Dragonfly

 

I'm pretty sure that this won't work - the torque wrench is still going to read or click at the torque it sees at the socket end. Adding length will only change how much force you have to apply to get it to read a given torque. If the wrench maxes out at 150 then you need a bigger torque wrench.

[grumpyvette]

adding LENGTH to the tq wrench handle will NOT change the tq readings it will mearly make it easier to apply the force necessary on the end of the handle to reach the readings

 

look you can buy what you need fairly cheaply, Ive got several TQ wrenches, and youll be surprized but most sears/husky/and similar priced tq wrenches are fairly consistant and reasonably accurate, and if your off by 1% or so IT WON,T MATTER A BIT

 

http://www.homedepot.com/webapp/wcs/stores/servlet/ProductDisplay?storeId=10051&productId=100058237&langId=-1&catalogId=10053&PID=1319015&URL=http://www.homedepot.com/webapp/wcs/stores/servlet/BuildLinkToHomeDepot?linktype=product&id=100058237&cpncode=08-42923053-2&AID=10368321&cj=true&srccode=cii_13736960

[grumpyvette]

btw

http://www.harborfreight.com/cpi/ctaf/displayitem.taf?Itemnumber=808

 

don,t bother, MY brother-in -law bought one, we tested it against several of mine, its NOT consistant

[Ferd/289]

grumpy..you are saying to NOT buy from HARBOR FREIGHT, but to buy from sears or home depot ie Husky brand, etc?

I have a click type to 150lbs, and spring indication type again to 150lbs. I never really checked for accuracy.

Anyway I will probably buy one from sears, I hate to borrow one from a parts store not knowing if its accurate.

Ferd

[Dragonfly]

I pretty sure that this won't work - the torque wrench is still going to read or click at the torque it sees at the socket end. Adding length will only change how much force you have to apply to get it to read a given torque. If the wrench maxes out at 150 then you need a bigger torque wrench.

 

I was a little concerned that it would not be understood which is why I also suggested borrowing one. The way it works is that you do not add the length to the handle of the wrench but rather you add the length to the wrench by attaching an extension that would look something like this O----C onto the 1/2" drive, this extension is parallel to the wrench handle not 90* from the handle. By doing that you have effectively increased the amount of rotational force (torque) for the same amount of force (weight i.e. how hard you push or pull the wrench), by doing this you can not use the dial or click to read your torque value you have to calculate the value.

 

Here is a link that gives a pretty good explination with pictures. http://www.specialpatrolgroup.co.uk/spooky/torque/torque.html

 

Dragonfly

[Dragonfly]

look you can buy what you need fairly cheaply, Ive got several TQ wrenches, and youll be surprized but most sears/husky/and similar priced tq wrenches are fairly consistant and reasonably accurate, and if your off by 1% or so IT WON,T MATTER A BIT

 

You are correct in that 1% won't matter. The wrenches that you are describing have a stated accuracy of 4% indicated value (IV) in a clockwise direction and a 6% IV in a counter clockwise direction. What is more important is repeatability which is what you get when you use a better built wrench which is what you get when you buy a better brand wrench.

 

Dragonfly (the Metrologist)

[Dragonfly]

Found a good link with a calculator and explination http://www.norbar.com/torquewrenchextensioncalculator.php

 

Dragonfly

[grumpyvette]

if you take the time to have these TQ wrenches tested (and I was lucky enought to have mine tested for free several times) by a buddy in the areo-space industry youll find that most exceed the listed acuracy percentage in REPEATABILITY & CONSISTANCY which is MY main concern and many are very close on the actual tq lbs

its

REPEATABILITY & CONSISTANCY that I look for more than the actual weight as I usually use ARP BOLTS OR STUDS and lube the threads and tighten and loosen the ARP BOLTS OR STUDS plus the fact that I USUALLY use a bolt stretch gauge on rod bolts

 

http://store.summitracing.com/partdetail.asp?autofilter=1&part=ARP%2D100%2D9942&N=700+115&autoview=sku

 

[Ferd/289]

Dragonfly, interesting solution that I never thought of. Really there is no reason not to use this solution.

[Tony D]

I have to go with Dragonfly on this one: Adding Length. (Though a 250 ft-lb 1/2" drive Torque Wrench is a kind of standard.)

 

If you use a "Crowsfoot" and are simply setting your torque on the wrench to specification, you are overtorquing your fastener! The difference between the crowsfoot drive center, and the effective center of the fastener is an increase in torque-arm length and will skew the torquewrench high in comparison to the set reading (it will click at the setting applied to the crowsfoot, but in reality is applying that to the lever arm of the crowsfoot to bolt centerline---in some cases 1/2")

 

This is common application in larger fasteners: a speciality wrench or 'extender' with a socket on one end, and a finite 6" distance between that socket centerline and the drive centerline. Many times it's simply a piece of 1/2" plate with a drive hole broached out and a socket welded on---this will give you a longer effective arm, and you must decrease the setting on the torquewrench accordingly or you will overtorque your fastener.

 

Same goes for a crowsfoot. Spending time working on Aerospace Structures and you realize how you grip your wrench and what you put on the end of the wrench makes a difference in the torque applied to the fastener!

 

There are crowsfeet wrenches made (like shown in the Nissan FSM for tightening the L-Head Ballstuds) that place the open-end directly under the square drive of the tool, and they don't require the torque arm recalculation. But standard crowsfeet do! 1%? Start checking what even 1/2" of center distance will do to your readings!

 

A prime example of 'get length' is the tool made for VW Axle nuts. They need 280 to 340 ft-lbs of torque. But EVERYBODY has a 250 ft-lb 1/2" drive wrench. You don't want to go out to buy a 3/4" drive just for the nuts. So they make a tool that is cut out of 3/8" plate, kind of 'egg shaped' with a 1 7/16" hex on one end, and a 1/2" drive square drive on the other end. Center to center distance on the holes is some predetermined distance...what it is allows you to set your torque wrench to 250 ft-lbs, but in reality you are actually applying 280 (or 340) ft-lbs on the fastener through the action of the legnthened torque arm. Cheaper than buying the new wrench! And on large fasteners this is very common.

 

Not everybody wants to buck up for the 3/4" drive 600 ft-lb Snap-On Torque Monster.

 

Now, anybody want to play with planetary gear driven reaction bar torque multipliers? 4:1 is good enough eh? 200 ft-lbs in, 800 ft-lbs out. Makes for airfreight of your tools much easier! LOL

[JMortensen]

Tony and Dragonfly have this right. I used the same principle testing breakaway pressure on my LSD. Made a long extension bar and then plugged in the torque wrench at the end. This allowed for less pressure at the handle and accordingly more accurate readings. Austin did the same and took pictures of his: http://forums.hybridz.org/showthread.php?t=117818

[Pop N Wood]

Just to add, beam type torque wrenches hold their calibration better than the click type. Makes them a better choice for the average motor head who doesn't have access to a calibration lab. They are cheaper too.

 

FWIW, the Navy required all torque wrenches used in the reactor plant to be recalibrated every 6 months.

[Dragonfly]

Just to add, beam type torque wrenches hold their calibration better than the click type. Makes them a better choice for the average motor head who doesn't have access to a calibration lab. They are cheaper too.

 

FWIW, the Navy required all torque wrenches used in the reactor plant to be recalibrated every 6 months.

 

You got that exactly right (in bold), the beam type is the most durable and has to be physically damaged to cause it to go out of calibration, but if it is ever damaged it can not be repaired and should be thrown away.

 

I never calibrated any of the Navy's reactor plant wrenches but the wrenches used on launch vehicles (rockets) have a 3 month calibration cycle.

 

Dragonfly

[Ferd/289]

I think I am going to buy a beam TW if they make them for 180 lbs or more? Is this a good choice?

[Dragonfly]

I think I am going to buy a beam TW if they make them for 180 lbs or more? Is this a good choice?

 

Yes and yes, they do make them and it is a good choice. I personaly will recomend that you look at the Craftsman (Sears) beam type wrench as it is one of the best out there and is a decent price. If you find one and you have never heard of the company that makes it (and its cheap) pass it up, they can not be adjusted.

 

Dragonfly

[Pop N Wood]

Here we go, pick it up at Sears

 

Low input Torque 160-190 in/lb. Can easily be applied by one person using standard 1/2 in. drive tools. Accuracy of +/-5%

 

 

http://www.sears.com/shc/s/p_10153_12605_00986520000P?vName=Tools&keyword=torque

[G.I.jonas]

wait, am i understanding that that puts out 8000 ft/lbs and costs $9000!!