Lubricating Threads

[jbasen]

For the holidays I received a Powermatic tenoning jig.  When I was assembling the jig I ran into a problem trying to adjust the miter bar so it fit tightly into the slot on my table saw.  The miter bar is adjusted by tightening 2 allen head set screws.  I believe that the screw holes for these 2 set screws are tapered and when you tighten the set screws into these holes it forces the bar to expand in width. 

The problem I ran into was that bar was fairly loose in my saws miter slot so I really had to tighten the set screws quite a bit trying to expand the bar enough to fit tightly into the slot.  In the process of tightening the screws they each stopped then jerked forward slightly farther and at that point were totally jammed.  I did everything I could to move them again to no avail. In fact I stripped 2 allen wrenches trying; even after applying penetrating oil.

I'm in the process of waiting for a replacement miter bar to arrive from Powermatic and my goal is not to have the same thing happen again.  I believe that the problem is that the threads on these screws were totally dry and if they had some sort of lubrication they wouldn't have locked in place. 

I'm looking for suggestion as to

1) What to lubricate them with. I've thought about using some blue thread lock, anti-sieze compound, or high pressure grease.  I emailed Powermatic about this but they haven't responded.

2) Is this the wrong approach and is there a better one

Thanks in advance for the help

 

[rvieceli]

you'll probably be better off to use anti sieze.
http://www.all-spec.com/loctite-anti-seize

 

[leakyroof]

Don't use Loc-tite since that will Not act as a lubricant.
Wax, oil, Anti-Seize will all help prevent the threads from binding

 

[Mort]

When I worked for a tire shop, I saw a test that showed that lightly lubricating the threads with motor oil produced the best clamping pressure. So that's what I'd use.

 

[leakyroof]

When I worked for a tire shop, I saw a test that showed that lightly lubricating the threads with motor oil produced the best clamping pressure. So that's what I'd use.

. That makes sense since many engine building manuals list lightly oiling the headbolts before installing them and torquing them to spec.

 

[RustE]

Straight SAE 20 or SAE 30 oil is good for consistent torque.  Not the detergent additive oil put in most vehicles.

To the original question, dry film lubricant would be my choice.

 

[Holmz]

I had a coffee grinder that seized up something fierce.
I finally got it apart with a lot of to-n-fro, but the thread had galled up some material.
After I got the thread cleaned up with a dental type of steel pick, I put polishing compound on and ran the parts together a few times.

Assuming that you have a problem with the threads, then that needs to be addressed first.
Maybe with a tap, or with the polishing compound trick.

Whether it is oil, or dry lube, something to keep then from galling makes sense after the basic problem is addressed.
(Assuming that they galled up in the first place)

 

[Cheese]

When I worked for a tire shop, I saw a test that showed that lightly lubricating the threads with motor oil produced the best clamping pressure.

That's absolutely mandatory when rebuilding anything that is subjected to high mechanical stress levels, be that an automobile engine or a bridge. A uniform and consistent fastening torque on the fasteners is mandatory for equalizing and consequently spreading stress levels on the assembled structure.

For the op's situation, I'd recommend using a synthetic oil as they have enhanced shear capabilities or an anti seize compound such as Never Seez. I have a 1# can of Never Seez Nuclear Grade Nickel on the workbench at all times.
http://www.neverseezproducts.com/antiseize.htm

 

[Holmz]

But... the nickel is pretty toxic and best reserved for things like exhaust systems where one needs the extra heat capability.
The copper based ones are just as good if the parts are not glowing red.

Any motor oil should work fine, and even olive oil would likely work. Or do a Marlin Brando, and use some butter.

Usually one uses dissimilar metals to avoid galling.
If the female thread is now bad then maybe a helicoil is needed.
I would probably not use a stainless screw as they seem to gall more easily.

 

[Cheese]

I would probably not use a stainless screw as they seem to gall more easily.

That's the reason you use a 410 stainless nut on a 304 stainless bolt...minimal galling. Or............you could just use Never Seez Nickel.....

 

[Holmz]

I figured the copper was 1/5th the price based upon the pennys/nickles factor ( [2cents] * 2.5)

 

[jbasen]

Thanks All!  I forgot to select notify for this thread.  I've been waiting for replies to show up in my inbox.  [doh]

After reading through all the responses I think I'll give anti-seize compound a try; as soon as UPS decides that the weather is good enough to deliver  [popcorn]

Thanks again.

 

[wptski]

Lubericating threads?  Well read what NGK the spark plug manufacturer has to say with pics.

 

[jbasen]

Thanks but this is not a situation where the set screws are designed to be tightened to a specific torque.  In fact it is quite the opposite situation.  Tightening the set screws is designed to incrementally spread the miter bar so the threads have to be in some way tapered so the tighter the set screw the more the miter bar spreads. 

 

[Cheese]

Well read what the spark plug manufacturer has to say with pics.

Well...the biggest problem in quoting this article is that ALL spark plug manufacturers recommend using a torque wrench when installing their respective spark plugs. They also recommend the use of an oil or some other lubricant (anti-seize) on the threads of the plugs in order to ensure a uniform tightening specification when installing the spark plugs.

Unfortunately, the typical mechanic will not use a torque wrench when installing the spark plugs because to him/her it seems to be an unnecessary encumbrance on a straight forward issue...just crank them down until the metal gasket seals...and then just give it a little bit more and the threads get stripped

What this dilemma can entail is a stripped spark plug hole.
Bottom line...it's imperative that some form of lubricant is used on threaded fasteners to ensure uniform loading on all bolts/fasteners.

Does it even make sense that a "dry" thread and a "wet" thread will in-situ be torqued to the same levels?

 

[Hurricane Whisperer]

I would try anti seize first as they are best for preventing galling and allow easy adjustment later on.

Anti seize compounds typically contain fine particles of metals such as copper or nickel to prevent the galling.  And withstand the high pressure of thread contact without getting squeezed out. 

Loctite threadlockers are stated to lubricate threads (before hardening) and reduce galling. They will also keep the screw from coming loose which may be a handy feature in this application as the mitre gauge may fit tight before the set screw reaches much tightness if the set screw.

 

[wptski]

Well...the biggest problem in quoting this article is that ALL spark plug manufacturers recommend using a torque wrench when installing their respective spark plugs. They also recommend the use of an oil or some other lubricant (anti-seize) on the threads of the plugs in order to ensure a uniform tightening specification when installing the spark plugs.

Unfortunately, the typical mechanic will not use a torque wrench when installing the spark plugs because to him/her it seems to be an unnecessary encumbrance on a straight forward issue...just crank them down until the metal gasket seals...and then just give it a little bit more and the threads get stripped

What this dilemma can entail is a stripped spark plug hole.
Bottom line...it's imperative that some form of lubricant is used on threaded fasteners to ensure uniform loading on all bolts/fasteners.

Does it even make sense that a "dry" thread and a "wet" thread will in-situ be torqued to the same levels?

Well here's two that don't agree with you.  One doesn't mention thread lubricant and the other states don't use any at all: Champion and Autolite

I've also seen where oiled bolts have split thin walled cast iron due to hydraulic action.

 

[wptski]

Loctite threadlockers are stated to lubricate threads (before hardening) and reduce galling. They will also keep the screw from coming loose which may be a handy feature in this application as the mitre gauge may fit tight before the set screw reaches much tightness if the set screw.

Thread lockers used in the production process are in a dry form so they don't pickup dirt because they come in massive amounts.