Re: Torque on drain bolts

[Bob MacFarland <emoto1@xxxxxxxxxxx>]

Minor, Bob wrote:

>I'm with you too, Tom.  Installing the drain plug by feel is simple; once it seats you can feel the washer crush as you continue to tighten. It doesn't take a lot of crush to make a seal and like you said, it certainly isn't going to fall out.  Same goes with the oil filter, seat it and tighten 1/2 to 3/4 turn and it always seals just like any other spin on oil filter.  Maybe those who haven't change oil in their vehicles for 30 years need a torque wrench, but I've been successful for a long time following that simple procedure.  
>  
>

You have to bear in mind that Falvio's original post was a request for 
the correct torque specs, as he had no confidence that his forearm was 
calibrated. We all make out own choices, and even though I made my 
living wrenching on bikes for a number of years, and have been changing 
oil on one thing or another since the 70s, I tend to use torque wrenches 
all the time. I actually enjoy it. Of course, when I was doing it 
professionally, I felt that I owed it to the customer to do everything 
by the book. That is one (perhaps the only) thing that I have in common 
with all of the best mechanics out there. Some folks have "the feel" to 
do it right by hand. No doubt about that.

If anyone wants a fun thing to try, take some bolt that you know the 
torque spec for and tighten it down by hand. Then put your torque wrench 
on it and tighten it to spec. You'll see if you didn't tighten it enough 
because it will have to turn some more before it reaches spec. An 
interesting exercise, especially if your buddies are there and beer is 
riding on the outcome!

Other comments below...


>The lower torque is not to save money.  I usually buy crush washers in every
>size a dozen at a time and put them in my tool box.   It's simply that, if
>I'm ever on the road and need a change and don't have a washer, I can reuse
>the old one if it's not destroyed with the stock torque.
>

If this is a concern, throw a spare washer in your tool pouch. I may do 
that, now that you have brought it up.

>
>The stripped threads thing is usually not a problem with BMWs if you use the
>stock torque, but it is an aluminum thread and can be stripped.  Make sure
>everything is clean.
>
>Anyway, to each his own, I guess.  Just letting people know that the BMW
>threads are very fine and put a lot of leverage on the bolt with not much
>force on the wrench and the aluminum crush washer serves as a lock washer
>too.  It keeps the bolt on if it's deformed and you don't back it off.
>

So now the crush washer is a lock washer? Can you also make gold from 
straw?  :-).

>
>If you always calibrate your $700 torque wrench and always torque to spec.,
>you certainly won't hurt anything except the crush washer and your knuckles
>when you try to remove the drain plug.
>

A $20.00 beam type torque wrench from Sears is quite accurate for it's 
entire life and needs no calibration. The click type torque wrenches do 
need periodic adjustment, but they're not that expensive and are good 
for tens of thousands of clicks before calibration is required.  It is 
best to use a torque wrench where the torque value you seek is near the 
middle of the wrench's range, especially for sensitive fasteners like 
cam bearing caps.

Bob

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