So I had the harmonic balancer off and sand blasted it without enough prior reflection. So sandblasted the outer surface that I now realize should mate with the crankshaft front seal The whole thing had so much gunk on it everywhere so the last thing it looked like was some sort of sealing surface. The plan is to put the balancer in a lathe and polish the seal mating surface. Before final assembly I want to put it onto the crankshaft and check the total runout at the seal surface. What is a reasonable tolerance of the total runout at this seal surface? I see SKF specifies 0.005 mm (0.0002 ") for industrial radial seals (see page 80 below). The chances it will get there or ever was there is quiet slim I think Many engine builders seem to accept 0.05 mm (0.002") runout at crankshaft bearing surfaces on non-race engines. Which isn't really comparable to a seal surface but anyway, maybe says something about the magnitude of numbers here. I am planning to put a modern radial type shaft seal in. Intuitively it feels a stock rope type seal would handle runout better, but that is just a guess. What do you say? https://www.skf.com/binaries/pub12/...SC_220121_EN_linked_18729_1_tcm_12-524179.pdf
Other seal manufacturers seem a bit more relaxed about this. Eriks group seem to state round 0.17 m.m. of shaft static eccentricity on a 36 m.m. shaft, reading from their graph: https://static.eriksgroup.com/en/oil-seals/brochures/oil seals technical manual/eriks - sealing technology - eccentricity and shaft oscillation.pdf GBSA then has similar numbers. I think I read around 0.007" (0.17 mm) in their table: https://www.gbsa.com/products/seals/oil-seals/oil-seals-shaft-and-bore-tolerances/ So 0.17 m.m eccentricity, that is like a cavemen flintaxe precision When finishing this sentence I also realize that this number is for the crankshaft. The balancer diameter is even larger and as such has an ever looser tolerance. Should be a cakewalk to achieve. Why is SKF sooo much more pedantic than others then... Maybe they specify general industrial applications and Eriks Group and GBSA refer to oil seals rather. Then Parker has some more info. https://www.parker.com/content/dam/Parker-com/Literature/Engineered-Polymer-Systems/5350.pdf The shaft surface shouldn't be too smooth (section 2-12). Would never have guessed! So what grit of emery cloth is good for the final touch then? Parkers document was the most informative, but they don't specify a number for runout/eccentricity. Sorry if I am spamming now, it turned out it was easier to find information than I first thought after figuring out what to search for. Conclusion A static runout of 0.17 mm (0.007") seems alright for this application, yet to determine is a proper grit for final polishing. Here I haven't found any as authoritative sources as for numbers on shaft eccentricity, but most people on forums seem to stop at somewhere 400-600 grit.
I've routinely polished the ugly part of driveshaft yokes that slide into trans tailshaft seals, axle shaft bearing and seal areas, dampers, etc. with 180-grit emery cloth, because that was what the shop supplied. For my own use, I've gone to 220.
Aha, there are sleeves. I am thinking, turning down the whole surface area to the next fit on radial seals might be an option too. Will be a bit painful for the next guy to find a seal though. EDIT: So it looks we sleeve it without even machining the the harmonic balancer. Well that puts that solution in a completely different light. Didn't realize we can leverage on the looser tolerances on seals compared to bushings bearings. I see there is also this one: https://www.summitracing.com/parts/fel-16203 Went by your advice, looks like I got a decent surface smoothness.
