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View Full Version : Adventures in M84 cleaning



jmcjr
08-02-2013, 01:27
Cleaned my scope and replaced the crosshair lens. Couple observations and recommendations.
Prep
1. Buy a high quality spanner wrench, cheap will be trouble. Thorlab has a quality wrench for $95.
2. I used white T-shirt material placed on a rimmed (1/2" tall rim), flat bake pan, prevents little screws and things from rolling away. Bright light to illuminate the pan.
3. Quality screwdriver for the windage and elevation unit screws.
4. Buy a manual or download the assembly layout. Keeps you sane when you drop a unit and it disassembles automatically.
4. Patience, (not my long suite) the sealant used for the scope is dried and resists removal of the scope parts.
Takedown
1. I did not disassemble the rear of the scope, the problems were all in the objective end.
2. Pop off the copper wire to your sunshade and slide it off.
3. Examine the scope window, remove it with the spanner wrench, do it slowly as there is a rubber gasket you can break under the window. Set it on the pan.
4. The objective cell assembly locking ring is next, before you remove it, count the number of turns needed to return it to the same position. Use the screwdrive to count the turns, my scope was 9 turns. There will be sealant on the locking ring and objective cell. Be careful you don't scratch/break the lens. As you remove the parts, place them sequentially into the pan.
5. Raise the windage and elevation caps and remove the four little screws holding them to the scope body. place in the pan. Do not disassemble the windage and elvation mechanism. Yuo can carefully unscrew them as an assembly and p[lace in the pan.
6. Locate and remve a set screw in front of the elevation assembly. Be careful, once this set screw is removed your reticle assembly will drop out of the scope.
7. Carefully tilt the scope and your reticle assembly will drop out, place in the pan.
8. Clean the lenses as assemblies, my scope had what looked like fungus on the reticle lens, it is actually delamination of the reticle, Sarco has new reticles, I could not clean the reticle, so replaced both the reticle lens and the frame. Made it much easier to fit new parts. The reticle assembly can be a challenge as it seems to want to fall apart, once the locking rings are out and you can hold the internal parts. A exploded diagram will save you lots of trial and error, mostly error. Clean /replace the parts. The sealant gunk is everywhere so cleaning will be essential to a clearer scope. I found no internal rust on my scope, just sealant. You can do trials with you reassembled reticle assembly without totally reassembling the scope. I pushed the reticle assembly into the scope, replaced, but not tightened the set screw and took a look, took a couple of times blowing air into the parts to remove dust. As I reassembled the scope, I put a small dot of nail polish to fix the locking rings. I had no sealant and doubt I would have used it.
9. I reversed the disassembly order from the pans to asssemble. Places to watch are 1. placement of the set screw retaining reticle assembly. 2. Carefully place the windage and elevation assemblies on the scope and turn the assembly into the scope body. Do not use the covers as leverage unless you want them to come off. Be sure your settings remain at mechanical zero. You will have to zero the scope so getting the units back on the scope body is essential.
More info than most want, but my scope is clear.