Loctite on torqued threads

Torque settings are derived from the stretch required in the bolt or stud, so for a con rod bolts you can use whatever you like on the thread as long as you tighten until the conrod bolt has extended in length by the required amount. As soon as you put something else on the thread but cannot measure the stretch then the torque figure given will be wrong as the toque figure is for a dry thread unless it specifies the thread lubricant (ARP supply a lubricant for use on their bolts and the torque figures they quote are for that lubricant only).

There are hundreds of loctite formula's and also activators that speed up the setting process, so I doubt you can say that the cambox issue did not occur, loctite is based on superglue technology and that will stick fingers together in seconds.

Here is one fast cure loctite

http://na.henkel-adhesives.com/product-search-1554.htm?nodeid=8797961158657&msdsLanguage=EN_US&selectedTab=technical

Hello Tony

I have great respect for your knowledge, although I held a different view on this subject of lubricating torqued threads.

Let's look at the Manx cambox failure as an example. The cambox design relies on the frictional contact between the gear and the cam FACES to transmit drive from the gear to the cam. We may think this is a poor design but it has won races for many years. There are 'vernier' pins sitting in holes in the two faces but these are for timing only and (despite misunderstanding of some) the pins are incapable of transmitting drive. Now I have to rely on memory, but we are talking about a fine thread of around 5/16" diameter on the nut and a torque of around 35 lbs/ft to ensure that the gear does drive the cam. When I put loctite on the (clean) threads and torqued to the desired figure that drive FAILED, the pins tore out a lump from the cam, bits jammed into the gears and it was luck that the piston did not strike a valve. The point I make is that this type of failure was KNOWN about by experienced engine builders and other Manxes had failed for the same build error.

It was said to me that under high pressure loctite will cure very rapidly, i.e. the chemical cure reaction is sensitive to temperature and pressure, as are all chemical reactions, and this effect is not at all surprising. EDIT - I have since searched the web and I can find no evidence for this view that loctite cures instantly under pressure. Why this loctite effect happened to me and others does not seem to be backed up by any other reports.

EDIT:- I have modified the following so as not to mislead future readers:

I had always believed that a lubricated thread is essential if the correct torque is to be delivered to the pressure surfaces. For example, if you fail to lubricate stainless steel threads and nuts they will gall and seize before any torque is applied. This happens to a lesser extent between steel and steel fittings. However, I now accept that aerospace practice is to use dry, clean threads for torqued fittings, wirelock if necessary, and apply anticorrosive to the outside of the fitting. Tony is quite correct in stating that the manufacturers regard loctite as a lubricant when torquing threads and that the torque applied may need to be reduced by 20% if dry fitting figures are being referred to.

In this edited text I apologise to Tony for previously suggesting that he was wrong.

Norm.