How do your remove screws that have thread lock compound applied?

[nevetslab]

Recently, while servicing an Ampeg SVT Heritage CL series amp, I encountered M3.5 pan head machine screws that had been installed with an abundance of thread locking compund at the factory, such as one of Loctite's produts. And, the screws used were soft steel, such that the Philips head pattern began to fail as attempts were made to unscrew them, to the point where they locked up from the compound. One screw head sheared right off on the AC Mains PCB assembly, with the chassis flange in the way inhibiting drilling out the broken screw shank.

I read applying heat directly to the head of the screw was an approach to use, though that was on a bolt at least 1/4-20 thread size.

Anyone have the tried-and-true solution to this kind of issue?

[drewl]

Usually a little alcohol loosens up the compound.

[Mark Black]

I have used the heat method with success. Soldering iron with "screwdriver" shaped tip.

[hodgy]

I've been successful with the soldering iron method on just about every screw I've tried it on.

[Mick Bailey]

Soldering iron works for me, too. Some compounds also loosen quickly with a drop of acetone applied.

A while back I did some trials with different locking compounds and found one that would shear a stock 8mm bolt threaded into a standard nut before it let go. Now either that's a reflection of how good the compound is, or how crap modern fasteners are.

[nevetslab]

While tearing down an Ampeg SVT3-Pro, which has the Talema Toroidal Power Xfmr held in place with 1/4-20 hardware threaded onto a carriage bolt, the nut was locked up with thread lock compound, neither holding the XFMR down, nor willing to move. Following your advise.....heat.....I grabbed my heat gun, and applied heat for a good 10 seconds or so. Worked like a charm....nut came free, hot enough to burn my fingers when it escaped wanting to head for the floor.

Thanks for the advise!!

[R.G.]

Thread locking compounds are generally some form of cyanoacrylate - "super glue" - and are usually subject to the same removal issues. I would try acetone if I could construct masking tape or modelling-clay dams to keep the stuff from eating other things, or heat. Cyanomethyl methacrylate based glues generally decomponse with heating. Good to know that soldering iron temp works.

The hobby machining world often uses "thread lockers" as temporary machining aids, holding parts together while some machining operation is done, then heating the assembly to break them loose.

The trick with a funny soldering iron tip works on epoxy potting compounds, too. A cheap soldering iron with a screw-in tip replaced by a stainless-steel screw that's been ground to a chisel tip makes a great UN-encapsulating tool.

[Jazz P Bass]

If all else fails, give the center of the screw head a good crack with a small hammer & a center punch.

[Mick Bailey]

The threadlockers I'm familiar with are the anaerobic acrylic monomers (usually ethyl or methyl methacrylate) that polymerize in the absence of oxygen and are further accelerated by the presence of metals. There's a huge choice and one of the criteria for selection is whether the fastener is intended to be removed using hand tools. I suspect that a lot of assemblies are put together with a high-strength retainer that's far stronger than necessary to just retain the threaded components in normal use. I sometimes come across equipment where the locking compound easily exceeds the shear-strength of the fastener and the location is such that applying heat or getting a solvent (even acetone or MEK) to penetrate into the joint is difficult.

[gbono]

The threadlockers I'm familiar with are the anaerobic acrylic monomers (usually ethyl or methyl methacrylate) that polymerize in the absence of oxygen and are further accelerated by the presence of metals.

Yes, it's the absence of oxygen and the presence of the metal threads that make an enviornment for thread lockers to work. There are various grades or "colors" to choose from - stick with the blue stuff on small hardware unless you want permanent connection.

There are also "patch lock" versions of hardware fasteners which usually have a "stripe" or ring of material to keep hardware from coming apart.

I see lots of gear where paint(?) is used to show if there has been any tampering - voiding the warrenty no doubt.

[Audiotexan]

Some good ideas above...though I haven't used my primary soldering iron for anything other than just solder in a LONG time because I'm 'anal' about keeping all substances that aren't solder/flux off my tip after a run in with a particular plastic that I never could quite fully remove (and therefor couldn't re-tin the tip properly). I do however keep an exacto around that I heat up for just such occasions. I'm one of those wierdos that think "a soldering iron is for soldering." (Right tool for the job kinda thing...it's not a prybar...nor hole maker for plastics...etc.)

I sometimes come across equipment where the locking compound easily exceeds the shear-strength of the fastener and the location is such that applying heat or getting a solvent (even acetone or MEK) to penetrate into the joint is difficult.

Wow, that's got to be some impressive stuff! I haven't ever run across anything that MEK wouldn't cut through.

Now penetrate OTOH...yeah, not the greatest. But complete removal from the surface area, down to bare "whatever" (usually metal) no problem. MEK would always do it a layer at a time if not the whole thing (especially after a light soak).