chain tension - allen key size

[dxtans]

Hello,

I do not understand the difference :  use 80Nm instead of 100Nm
when you have (copper) greased the spindle. Surely the nut should be the tightened to the spec of 100Nm.
What am I not understanding here.

Thanks
dxtans

[greywolf]

The grease lowers the friction of the threads so a lower torque stretches the lubricated bolt about the same amount as the higher torque stretches the non lubricated bolt, or axle in this case. There have been many posts of dry galled axle nuts on V-Strom forums. I have been advocating using anti seize and 80Nm for years with zero reports of problems, which is more than I can say for the stock recommendation.

The amount of torque reduction to offset lubrication varies depending on the materials and lubricant. This chart shows a greater reduction to under 50% for waxed fasteners for example. http://zerofast.com/torque.htm

The 80% I've suggested came from a chart on oiled bolts and has been working in practice for years.

[Jacko]

Tightening a nut to 100Nm that has been greased will equate to around 120Nm of pressure on the threads from a non greased fastening. It's basic physics, it will present less friction and therefore turn more before it hits a specific torque.

A simple demonstration would be to clean the threads of both axle and nut with something like brake cleaner, so it's oil free, then tighten to, say 60Nm (the figure itself is unimportant). Then mark the nut and swing arm position relation, then undo and cover the threads in grease and repeat, the nut will continue to spin past the mark before 60Nm is reached, thereby actually putting more pressure through the bolt (axle) for the same torque. To counter this we drop the torque setting.

[Strommer]

Agree with the 80% for lubed nuts.  My threadlock btw says not to reduce torque, despite being wet.  Worth remembering.

[iansoady]

I picked this chart up from somewhere on the web:

.

Greywolf is right, it's the stretch in the bolt that keeps it tight (or deforms it if too much). A lot of bolts, eg head bolts on my Land Rover TD5 engine, are tightened to a specific torque then turned through a specified angle.

[Jacko]

No copper grease in that chart.

[iansoady]

That is of course true. However, it should act as a guide.

[Jacko]

Yes, of course, great find. I'm just puzzled as to why the most popular anti-seize agent isn't present in such an otherwise comprehensive list.

[iansoady]

I don't know, and can't now remember where I found it - a quick google doesn't show it up. I have it as part of a comprehensive set of spreadsheets with spanner / bolt sizes, tapping drills, etc etc which I've been accumulating for years.

Although I have a tin of copaslip I generally use a light smear of HMP grease for fasteners I'm likely to be undoing in the future. I find copaslip (which the previous owner / mechanic of my Wee was a great fan of) rather messy and not really an improvement. I also have an aerosol of an aluminium based ant-seize compound that I use on the back of car wheels etc.

[greywolf]

Yes, of course, great find. I'm just puzzled as to why the most popular anti-seize agent isn't present in such an otherwise comprehensive list.

Copper Grease is a STEL trade name. http://www.copper-grease.com/index.html
It's an anti seize compound containing copper. You won't find it mentioned much outside the UK. Ask them why they don't supply that information. I don't even see it mentioned at the web site.