Solvent for Loctite?
I have a project, 4 broken 8mm SHCS's on the face of a piston. 3 have stubs sticking up, but they will not budge, with moderate heat. This is inside a housing, with little space to work, and I will have to use a small right angle drill to drill a hole in the one that is broken off flush. There is a seal right behind the face of the piston, so I cannot use much heat. Hero or Zero type project, the only other option is to tear down the entire end of the machine, which will require many new seals. Are there any chemicals that will dissolve Loctite?
I believe the active material in LocTite is an acrylic-base adhesive, which means that the solvents useful for cementing acrylic parts together will have some effect, such as methylene chloride, or acetone to a much smaller extent. The problems in using solvents is the very small amount of area available for the solvent to work on the LocTite down inside the engaged screw thread. If ther is some way to soak the part by submerging in solvent, that may work. I have done this before, and been somewhat successful, but it can take days.
Had some powder coated parts that had some loctite'd pieces in them that I needed to get out, tiny little screw head so it kept stripping.
The solution was a soldering iron on the heads, kept the heat nice and local.
Loc Tite is a cyanoacrylate. Others have had success with acetone. Hobby shops sell Super Glue solvent, which should work. Heat on the screw heads both softens the Loc Tite and expands the screw. Since the heat transfer across the thread contact area is poor, applying the heat to the screw and not the part will make the screw expand and crush the Loc Tite, further loosening it.
As mentioned any solvent for acrylic will be a solvent for Loctite, but any of these solvents may also damage the seals, even the vapors could permeate into the seal material causing it to soften and swell.
It is possible the soldering iron on the screws is the safest approach.
You did not mention the grade (type, or color) of locktite that was originally
If it was the red, permanent stuff, and the parts were properly prepared by
de-greasing before assembly, I would say you will have a very very tough
time getting them apart without the application of substantial heat.
In my case it was a pair of shift fork shafts on a jeep transmission that had
the locking screws installed that way. I finally had to resort the application
of flame in the form of an air-acetylene torch to remove the screws.
I was able to do this without dismantling the gearbox very far, fortunately.
My only other suggestion is that the locktite company has a very good web
site. You might look there, or even call one of their application engineers.
My first attempts are always to weld a nut to the stub the heat frm the weld will wick in and walla. used this approach many many times successfully.
Loctite sells a solvent based on Nitromethane - I think it is called XNMS.
Locktite 755 is a solvent for thinning locktite, might not break it loose.
If you can heat the studs and melt Bees Wax into the threads, that will kill it every time.
I use MEK ( methyl ethyl ketone) available at the hardware for plastic pipe primer. I soak hyd. pistons in it to dissolve the loctite out of the threads.
Permatex Gasket Remover works, but you have to let it soak for a while. This was recommended by Loctite in one of their TDS's.
try putting a heat sink
to draw the excessive heat away from the seal areas.
I did have a similar situation in having to remove a stubborn rounded nut on the shaft's end and a seal was close by. This method worked.
Use your judgement as to how close the seals are and what sort of heat they can take. Perhaps cooling the seal area might give you enough time to apply a torch to the parts that need freeing.
Anything can be used as a heat sink to draw and absorb excessive heat from critical parts of the assembly.
Wet rags are simple and can be moulded around the part. Just bear in mind the potential fire hazard!
I have heard of someone using a large potato cut in half and stuck through a 1/2 inch sealed shaft that needed heating in situ.
Alternatively, try a thick piece of metal in full surface contact with the heated area closest to the seals.
If you want to try acetone, ladies use variations of it all the time to remove nail varnish. Some brands might contain very little acetone and therefore weak for your application, so ask the chemist to give you the best one for the job.
I am not an engineer or chemist, but consider the following (guys, pitch in!):
Maybe it isn't the loctite as much as it is a super tight fit, or a standard old stuck bolt. If that is the case, then applying heat will be COUNTERproductive if only the fastener is heated, and none of the heat transmits to the piston. I tried running the numbers on the expansion of alloy steel (the fastener) and came up with this- if you assume that the fastener and the piston are at 70 degrees F, and you apply localized heat to the fastener and none of it is transferred to the piston (it remains at 70 degrees) then the 8mm fastener will increase in diameter by .000185 inches (sorry for the mixed units) in a hole that has not enlarged, resulting in an even tighter fit! If, OTOH, the fastener is cooled to 0 degrees F (use dry ice or liquid nitrogen, freon, etc) then the fastener will reduce its diameter by the same .000185 inches, making for a (slightly) looser fit.
Is this correct, guys?
If this flies with the wiser members of the forum, I might be inclined to warm the piston as much as possible and then hit the fastener with the cooling agent. With luck you might be able to get a 140 degree difference, resulting in a "whopping" .00037 inches additional clearance.
Thanks for the ideas. I spent several hours trying to get the stubs out. and realized that it was easier to tear the machine apart, machine the stubs flat, and drill a new set of holes. In fact, I am going to drill 2 full sets of holes, in case this happens again, they can cut off the bolts and use the extra holes.