Thread: AA Workshop Basics

as in accordance with RTFM and general cleanlyness thread cleaning is an important thing as it enables correct torquing... Speaking of correct torquing.

Theres a lot of bolts and a lot of ways to do them up some of them are seemingly quite large bolts with reasonabley low values. Others are quite large with respectabley HUGE torque values. The first type you just to up with a torque wrench and you can reuse them almost as many times as you like the second you get to do up one time and one time only. This type of bolt is normally a torque to yield fastener and it achieves its maximum tension just before it goes all marshmellowy then snaps.

before you start to torque a bolt you need to check the following things.

1. Thread type. Is it the same, theres a lot of different thread forms and sizes out there some of them are close enough to work together but arent.
2. Thread condition. is the thread useable, damaged, contaminated
3. Grade. Is it the right grade for the job? putting to high a grade bolt in can have just a bad result as too low a grade.
4. Material. Is the fastner your about to use the correct material for the job. Did you just put a stainless steel nut onto an aluminium bolt?
5. Lock and Lube. Before you put it in do you need oil, loctite, spring washer,nyloc?
6. Torque Scale. Am I doing it up to inch pound, foot pound, Newton Meters, Kilogram meters Grams/Centimeter or something even more obscure? If you're using the rattle gun dont forget that rattlepascles are different to doogameters.

Once youve got all that done you can have a go at putting it together. Use the correct tool for the job, Tight then belt it with a hammer or rolling it up till the rattlegun stops is an excelent way to produce this, a variable pitch form thread that starts out with a 1.5mm pitch and heads into 1.75mm.

Heres the normal thread, this is where the thread was engaged into the fastner so it couldnt stretch.

lead thread1-50.jpg

heres the bit where the thread didnt make it into the casting and being the weakest bit of the bolt this is where the initial stretching began. Much more torque and this bolt would have let go.

thread stretched1-75.jpg

and here it is in side profile on the thread gauge thats part of my thread file.

thread change.jpg

If you're lucky a snapped off bolt just means an extra hour or so worth of inconvenience as you battle whats left out with the easy outs, drill outs and any other means you can think off. Worst case you melt down a handfull of grands worth of engine. If the manual specifies a torque, use a torque wrench and be sure that its in calibration. If the manual says to just do it up then you're supposed to do it up to the standard torque for the diameter fixing and thread form. These are easy to look up on the net and are avialable at a small cost from professional fixing suppliers and no, just because supercheap and autobahn sell blister boxes with nuts and bolts in them they are not professional suppliers.

Ok so assuming youve got all the above sorted and have a decent calibrated torque wrench to start with, how do you do angle torquing without a torque angle gauge.

For starters you dont use the torque wrench, once the initial torquing is done put it back in its box some where safe and break out the big breaker bar your scribe and your paint pen.

for startes your average bolt is 6 sided and your average socket is 12 sided which means you have 30 degree offsets easily positioned ready to use. all you need is a little prep work

boltpaint.jpg
paint the area around the bolt and put a marker point on the bolt
scribe paint.jpg
Scribe the paint inline with a point of the bolt the scribe mark on this one is way too wide but its only to demo the concept usually you make a skinny mark.
paintsocket.jpg
paint the socket and place it on the fixture up against the existing paint, rotate it firmly in the direction of tighten so that there is no slack between the head and the socket
scribe socket.jpg
Scribe mark the socket exactly in line with your existing scribe mark
offsetsocket.jpg
Remove and rotate the socket the required number of points to get your required torque angle (this image shows 30 degrees)

and once youve turned it all so that the scribe marks line up again you're done for that phase of tightening. (this images shows a 60 degree rotation)
doneturn.jpg

Heres a sketch of how it all works out since the photos were a bit blurry.

angles up.jpg

Remember the key to angle torquing is as it is with all torquings.
Slowly
Smoothly
in Stages
in Sequence

If you yank it around or it starts to jerk and bind you increase the risk of damage and incorrect setting, if you crank down one bolt all the way to its maximum tension you can warp/misalign the casing or plate you're working on and the sequence is pretty much the same reason.