They're really just an inefficient lil vacuum cleaner
Something around 400 and 800 grit and a lubricant that trips your trigger...give er take.
Everyones got their own voodoo formula. I prefer the the squeezens from a ripe banana and some comet; but the banana must be picked in Havana during the full moon or your results may vary.
400 to 800 is roughly around the size of all the crud and corruption the gear train normally eats over time. The idea is to simulate in short fashion, a gear set that has been well broken in over time. Under magnification, my observation has always been that T-jets are dirty nasting tar burning beasties. You can polish it to perfection but everything returns to it's naturally scuffed state after some use. I'm not trying to make light of a top five in the fundamental build process, but the idea is to hone in the optimum running clearance with a minimum amount of fan fare and call it good. Most especially after you've scrambled up gear sets. Extra drama time is better spent on selecting good gears in the first place or better yet, pick up shoe voodoo. Lapping should be a one and done process.
LOL @ Al...I'm sure Jim is just expiditing the process in his own way by using ashtray sand, obviously some stuff cuts quicker than others and for the inexperienced is best to sneak up on the process and learn the intricasys . It's been proven time and time again that there is more than one path. I just snip up some small squares of 600 wet and dry carefully polish the top and bottom gear sides on a running gear set with synthetic motor oil. The freed abrasive mixes with the oil and creates the exact slurry we require. I just use an old Aurora tranny and press the contacts against the screws with the chassis front tilted downwards so the spent slurry drools out neatly to the front of the gear plate. Once I hear that the "no go" point is achieved, I spritz the chassis with electrical parts cleaner, then blow it off, and re-lube.
In most cases there's no need for the insanity lappings. No sloppy prolonged immersions in tubs of secret potions, or slathering the contents tubes of high dollar goo and flinging it on yer shirt. Papering the gear set properly cures a multitude of ills. For the special builds, your chosen rouge goes any where 600 paper cant by applying it with the model murdering specialty application tool part # 0001 (aka der toothpick).
Enough lapping is just right, and too much is called excessive wear. Simply put it's and ear thing and the process itself must be developed to suit yourself and your own bench/needs.
Last edited by Bill Hall; 09-06-2013 at 11:17 PM.