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showbizkid
02-08-2007, 11:51 AM
We had a Loctite rep at our chapter meeting a couple of months back who said that you need to adjust torque values when tightening bolts with Loctite applied (naturally), and said there were charts on their website with adjustment values. But there aren't, so I called them and the service rep said, basically, to adjust torque value as if adjusting "for a lightly oiled bolt."

Well, this is pretty vague. Does anyone here have a hard-and-fast formula?


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Clark in San Diego
'63 F2/Lark Standard
http://studeblogger.blogspot.com

hank63
02-09-2007, 09:53 AM
Torque-tightening is a very inexact science. Most torque figures are given for clean, undamaged and lightly oiled fastener threads. The objective is not the torque figure itself, but a certain tension in the bolt (which is difficult to measure).
Unless somebody else can provide what you're asking about, I'd make sure the threads are all clean, undamaged and lightly oiled and then tighten to the recommended values.
If you have to tighten in steps, ensure the last step is reasonably big. Do not stop just below recommended torque, with the intention of applying a little more.
Use an indicating wrench if you can. Otherwise, stop as soon as the clicking wrench "clicks".
/H

r1lark
02-12-2007, 12:49 PM
quote:Originally posted by showbizkid

We had a Loctite rep at our chapter meeting a couple of months back who said that you need to adjust torque values when tightening bolts with Loctite applied (naturally), and said there were charts on their website with adjustment values. But there aren't, so I called them and the service rep said, basically, to adjust torque value as if adjusting "for a lightly oiled bolt."

Well, this is pretty vague. Does anyone here have a hard-and-fast formula?


[img=left]http://members.cox.net/clarknovak/lark.gif[/img=left]

Clark in San Diego
'63 F2/Lark Standard
http://studeblogger.blogspot.com


This is a good question, that really got me to wondering about it too! A search of the Loctite website found nothing, same as you. Did some Google searches at work (it's ok, I work in a power plant and we use Loctite quite a bit, so being the good Equipment Engineer that I am, this is 'need to know' information<G>) and didn't find much. Finally I submitted a question to Loctite's Technical group. This is the response:
Paul, to put this in simple terms, the liquid products provide lubricity when you torque an assembly down and they often mimic "oil only" values. In some cases, they're even more lubricating then oil. So they will reduce your torque [requirements]. The stick products also provide some lubricity, but not as much as liquid products. The TDS's show some numbers and the TDS for stick 248 shows slightly more lubricity versus a dry thread. Please test under your own actual conditions.
Regards, Mike Smigel

I added the word "requirements". Loctite has a threadlocker that comes in a stick, so that is what the "stick 258" is referring to. So, for what it is worth, that is Loctite's answer.

As mentioned, little was found with my Google searches. The following was about the best found at http://pweb.jps.net/~snowbum/torquevalues.htm, which appears to be a BMW motorcycle site:
When threads are clean and dry, and then Loctite is used on them, as a rough guide, Loctite causes about a 15% increase in actual torque (acts as a very mild lubricant). Because of the safety factor of parts strengths and typical usages, the effect of Loctite is usually ignored, as far as torque wrench settings are concerned. This is NOT SO when using antiseize compound...you should, and in many cases (spark plug threads) MUST allow for the change (30% approximately with antiseize compound).

Clearly the Loctite adds some lubricity. How much is dependant on the type of Loctite. IMHO, when using it on small bolting (1/4" and less) you would need to be very careful about your torque values. On larger fasteners, especially with quality high strength bolting, the effect may be negligible. But the safest method when using Loctite may be to make the corrections required for a lighly lubricated fastener.

Paul

Visit The Studebaker Skytop Registry website at: http://hometown.aol.com/r1skytop/myhomepage/index.html

Roscomacaw
02-12-2007, 03:46 PM
From the Studebaker shop manual regarding the reinstallation and torquing of the head bolts: "To avoid incorrect cap screw (bolt) tightening due to excess friction in the cap screw threads, dip the cap screws in engine oil or graphite paste before starting them into the cylinder block."

Miscreant adrift in
the BerStuda Triangle
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1957 Transtar 1/2ton
1960 Larkvertible V8
1958 Provincial wagon
1953 Commander coupe

showbizkid
02-12-2007, 07:23 PM
This is really interesting! I'm assuming that Studebaker recommended that procedure only for the head bolts.

Extrapolating from what Paul discovered, then, let's assume we have a 3/8" bolt that's specified for 75 foot-pounds of torque. If I applied 242 (medium-strength blue) to it, I would instead tighten it to about 64 lbs/ft (75 lbs. -15%).

Sound about right? (I'm too anal-retentive for my own good sometimes [8)] )


[img=left]http://members.cox.net/clarknovak/lark.gif[/img=left]

Clark in San Diego
'63 F2/Lark Standard
http://studeblogger.blogspot.com

hank63
02-13-2007, 09:35 AM
Another thing to bear in mind - torque wrenches are not exact. A typical wrench might have 5% error. Beware - this is 5% of maximum scale value.
If we have a 1000Nm wrench, the error becomes 50Nm. This 50Nm stays the same even if you use the wrench to tighten to 200Nm only. Then you would have a 25% error possibility.
Therefore, use a wrench with a max value close to what you intend to apply.
/H

StudeRich
02-14-2007, 08:18 PM
The whole concept of Locktite use on Studebakers seems to me to be a mute point. The only place I have ever needed to use the stuff is where there is a good amount of vibration on a critical part. The only such place I know of, is on the '63-'66 Disc. Brake mounting bracket (3) 3/8 screws that do tend to loosen and proceed to destroy your entire brake setup. At Frost & French Studebaker we used to use Teflon Button bolts to secure those little devils!

StudeRich
Studebakers Northwest
Ferndale, WA