Jammed Truss Rod

[hollowbody]

Hi, I dug out my Loar LM-110-BRB mandolin after a few years of not playing it to find the action was high and the neck bowed. It's a relatively new Chinese made model so I set about trying to adjust the Truss Rod however the truss rod is jammed. I've definitely got the correct hex key at 5/16" but it won't budge either way.

I'm wary of pushing it too far and busting the thread so hoping some of you kind people can come up with some suggestions!

The manufacturer says it is a Two-way adjustable truss rod.

Thanks

[hubrad]

It might just be ever so slightly rusted in place if not touched for years. You could try just a drop of penetrating oil like wd40 on a pin or bit of wire to get it to the rod cap.
If it looks like the hole in the cap where the hex key fits gives access to the end of the thread then drop it in there. If that hole looks solid bottom then hope for access down the side to where the cap meets the end of the rod. All this may, of course, be really difficult to view clearly!
Try not to drop oil on the wood, but don't totally panic for the odd drop or smear.
If this sounds too much, consult your local luthier.

[pops1]

I would use an actual penetrating oil. WD40 is 60% water and while it may work something like Deep Creep will work better. Be sure to use the straw to get pin point accuracy to the threads.

[MikeEdgerton]

...WD40 is 60% water ...

You might want to do a little research on that. The WD stands Water Displacement and the 40 isn't a percentage. It's a penetrating oil.

50–60% naphtha (petroleum), hydrotreated heavy. <25% petroleum base oils. <10% naphtha (petroleum), hydrodesulfurized heavy (contains: 1,2,4-trimethyl benzene, 1,3,5-trimethyl benzene, xylene, mixed isomers) 2–4% carbon dioxide.

[pops1]

I stand corrected, thanks again Mike. It was something I read decades ago about displacing water in a distributor, even tho it contained water. It definitely does that as I have used it for water displacement many times. Displacing water is not what is called for here, but penetrating oil of some sort would be more appropriate. While the can of WD 40 that I have says it loosens sticky parts, it doesn't say anything about being a penetrating oil, I think the Deep Creep, or something similar, would do a better job as it is made specifically for that purpose.

[sunburst]

Any oil will get into the wood, perhaps permanently. I wouldn't use oil on a truss rod in a neck.
First of all, don't be afraid to use a fair amount of force to turn the wrench. Too much force can cause damage, but it is difficult to apply that much force with a hex key (without a "cheater bar").
If it just simply won't move, I would try heat. Get a long hex wrench (Allen wrench), put it in the socket of the truss rod and heat the wrench until the heat transfers to the rod, then try turning. Of course, you'll have to use something besides bare hands to turn the hot wrench. I've released rods that had become epoxied in place in neck and were thus useless, so quite a bit of heat can be applied before damage occurs, but still, caution is in order when heating.

[Steve Mead]

Way back when I had one of "The Loars" the only hex key that would fit properly due to the angle was a ball end hex key. Might be worth a try so you do not strip it.

[rickbella]

You also might consider Break Free. They developed it for jammed firearms, but it works on everything that is stuck:

https://www.ebay.com/itm/25605045685...SABEgLEaPD_BwE

[Jeff Mando]

I would probably say WD-40 is the greatest invention of the 20th Century. The only thing I object to is the smell.

Walt Kowalski toolbox contains 3 items -- WD-40, vice grips, and duct tape. Supposedly "any man worth his salt can fix almost any problem with this stuff!"

My former bandmates still mention from 30 years ago on tour, van broke down in Iowa farmland on a Sunday afternoon. Busted radiator hose. I improvised by taking a can of spray paint, emptying the paint, making a tube by sawing off the ends with a hacksaw, wiping it out and attaching to the broken section with 2 clamps. Got to the gig, OK. Took about an hour, but at least it wasn't raining or cold....

[Richard500]

Often, ATF (transmission fluid) plus acetone is preferred by connoisseurs of rusty fasteners, but still is hydrocarbon oil and a very strong solvent, that, if liberally applied, may get to finishes. I’m thinking (no longer my job) that if the neck bow is severe, the truss rod is now under high stress, making the nut even harder to turn, so I’d first take the tension off the strings. Of course, the factory installation of said rod might also have involved cross-threading, or even bad threads. Car companies used to install trim screws using hammers…

[HoGo]

You can also clamp the neck against stiff metal bar to "prebend" it slightly in opposite direction which may help to loosen the rod for adjustment.