spacewrench
Plastic
- Joined
- Apr 2, 2020
Hi, I'm a patent lawyer and motorcyclist, and in no way a machinist or even mechanic. Unfortunately, due to a stripped clutch spline, I'm obliged to dive into both; I need to open a three-shaft, six-speed transmission and replace an input shaft that has a gear, a couple of bearings, and some other gadgets pressed or slid onto it.
The service manual procedure includes a section to measure and shim (if necessary) the transmission shafts to within +0-0.002" over bearing-to-bearing distances of about 8". The procedure is to set up a dial indicator against a reference cylinder, then measure/shim the shafts. (Of course, I don't have the reference cylinder, so I guess I'll have to measure against the two shafts I don't have to fool with.)
I am comfortable working with 0.002-0.012 over short distances (such as intake & exhaust valves) but have never had to measure a large, freestanding object to 1 part in 4000; it seems implausible that you can do this reliably outside of a pretty controlled environment.
I'm hoping that my fear is unfounded, and that with a few simple things you learn the first day at machinists' school, even a hamfisted fool can measure a part like this successfully.
Thus my question: is there a good reference for beginner stuff like this? Is it 2-3 tips that you can put in a reply post? Is this whole measurement thing likely a snipe hunt that the BMW guys are having a laugh over?
Thanks for any help -- I haven't disassembled all the way into the transmission yet, but hope to get there in the next week or so.
The service manual procedure includes a section to measure and shim (if necessary) the transmission shafts to within +0-0.002" over bearing-to-bearing distances of about 8". The procedure is to set up a dial indicator against a reference cylinder, then measure/shim the shafts. (Of course, I don't have the reference cylinder, so I guess I'll have to measure against the two shafts I don't have to fool with.)
I am comfortable working with 0.002-0.012 over short distances (such as intake & exhaust valves) but have never had to measure a large, freestanding object to 1 part in 4000; it seems implausible that you can do this reliably outside of a pretty controlled environment.
I'm hoping that my fear is unfounded, and that with a few simple things you learn the first day at machinists' school, even a hamfisted fool can measure a part like this successfully.
Thus my question: is there a good reference for beginner stuff like this? Is it 2-3 tips that you can put in a reply post? Is this whole measurement thing likely a snipe hunt that the BMW guys are having a laugh over?
Thanks for any help -- I haven't disassembled all the way into the transmission yet, but hope to get there in the next week or so.